Tuesday, July 31, 2007

Origins of social groups in infancy

Kinzler et al. report interesting observations on how language influences the selection of social groups by human infants.

What leads humans to divide the social world into groups, preferring their own group and disfavoring others? Experiments with infants and young children suggest these tendencies are based on predispositions that emerge early in life and depend, in part, on natural language. Young infants prefer to look at a person who previously spoke their native language. Older infants preferentially accept toys from native-language speakers, and preschool children preferentially select native-language speakers as friends. Variations in accent are sufficient to evoke these social preferences, which are observed in infants before they produce or comprehend speech and are exhibited by children even when they comprehend the foreign-accented speech. Early-developing preferences for native-language speakers may serve as a foundation for later-developing preferences and conflicts among social groups.
And here is the fascinating introduction to the article, whose PDF version can be obtained here.
The Gileadites captured the fords of the Jordan leading to Ephraim, and whenever a survivour of Ephraim said, "Let me go over," the men of Gilead asked him, "Are you an Ephraimite?" If he replied, "No," they said, "All right, say ‘Shibboleth’." If he said, "Sibboleth," because he could not pronounce the word correctly, they seized him and killed him at the fords of the Jordan. Forty-two thousand Ephraimites were killed at that time.

Judges 12:5–6.

The biblical story of Shibboleth speaks of the ancient massacre of those who could not correctly pronounce a phrase, thereby revealing their out-group status. Modern-day Shibboleth is ubiquitous: United States history alone abounds with examples of linguistic discrimination, from the severing of the tongues of slaves who spoke no English, to the forbidding of the public speaking of German during World War II and the execution of Russian speakers after the Alaskan purchase (1). Recent world history provides examples of linguicide paired with genocide of the Kurds in Turkey (2) and of imposed language policies initiating anti-Apartheid riots in South Africa (3). Favor for one's native language group pervades contemporary politics in more subtle ways as well, for example, in recent debates concerning bilingual education, the politics of sign languages in deaf education, or proposals to make English the national language of the United States. We present evidence that the connection between language and human social groups has roots in human infancy, where it guides early-developing social preferences and predisposes humans to interact with members of their own linguistic group.

Interactions between native and second languages in the brain

It is known from fMRI imaging studies that second languages can recruit brain areas not activated by the native language, and damage to these areas caused by strokes can compromise one language more than the other. Theirry and Wu now show that unconscious interaction and translation occurs between the two systems:

Whether the native language of bilingual individuals is active during second-language comprehension is the subject of lively debate. Studies of bilingualism have often used a mix of first- and second-language words, thereby creating an artificial "dual-language" context. Here, using event-related brain potentials, we demonstrate implicit access to the first language when bilinguals read words exclusively in their second language. Chinese–English bilinguals were required to decide whether English words presented in pairs were related in meaning or not; they were unaware of the fact that half of the words concealed a character repetition when translated into Chinese. Whereas the hidden factor failed to affect behavioral performance, it significantly modulated brain potentials in the expected direction, establishing that English words were automatically and unconsciously translated into Chinese. Critically, the same modulation was found in Chinese monolinguals reading the same words in Chinese, i.e., when Chinese character repetition was evident. Finally, we replicated this pattern of results in the auditory modality by using a listening comprehension task. These findings demonstrate that native-language activation is an unconscious correlate of second-language comprehension.

Monday, July 30, 2007

What drives evolution - natural selection or mutations?

Here is another perspective article, from Masotoshi Nei (PDE here), on what may be a paradigm shift in evolutionary theory.

Recent studies of developmental biology have shown that the genes controlling phenotypic characters expressed in the early stage of development are highly conserved and that recent evolutionary changes have occurred primarily in the characters expressed in later stages of development. Even the genes controlling the latter characters are generally conserved, but there is a large component of neutral or nearly neutral genetic variation within and between closely related species. Phenotypic evolution occurs primarily by mutation of genes that interact with one another in the developmental process. The enormous amount of phenotypic diversity among different phyla or classes of organisms is a product of accumulation of novel mutations and their conservation that have facilitated adaptation to different environments. Novel mutations may be incorporated into the genome by natural selection (elimination of preexisting genotypes) or by random processes such as genetic and genomic drift. However, once the mutations are incorporated into the genome, they may generate developmental constraints that will affect the future direction of phenotypic evolution. It appears that the driving force of phenotypic evolution is mutation, and natural selection is of secondary importance.

Neural correlates of understanding concrete versus abstract words

Pexman et al. have used functional MRI to evaluate several different theories of semantic (meaning) representation that attempt to explain why concrete words (CARROT) are recognized and remembered more readily than abstract words (TRUTH). Clips from their abstract:

This concreteness effect has historically been explained by two theories of semantic representation: dual-coding...and context-availability. Past efforts to adjudicate between these theories using functional magnetic resonance imaging have produced mixed results. Using event-related functional magnetic resonance imaging, we reexamined this issue with a semantic categorization task that allowed for uniform semantic judgments of concrete and abstract words. The participants were 20 healthy adults. Functional analyses contrasted activation associated with concrete and abstract meanings of ambiguous and unambiguous words. Results showed that for both ambiguous and unambiguous words, abstract meanings were associated with more widespread cortical activation than concrete meanings in numerous regions associated with semantic processing, including temporal, parietal, and frontal cortices. These results are inconsistent with both dual-coding and context-availability theories, as these theories propose that the representations of abstract concepts are relatively impoverished. Our results suggest, instead, that semantic retrieval of abstract concepts involves a network of association areas. We argue that this finding is compatible with a theory of semantic representation such as Barsalou's perceptual symbol systems, whereby concrete and abstract concepts are represented by similar mechanisms but with differences in focal content.

Friday, July 27, 2007

The genuine problem of consciousness

Jack, Robbins, and Roepstorff suggest (PDF here) that:

...popular conceptions of the problem of consciousness, epitomized by David Chalmers' formulation of the 'hard problem', can be best explained as a cognitive illusion, which arises as a by-product of our cognitive architecture. We present evidence from numerous sources to support our claim that we have a specialized system for thinking about phenomenal states, and that an inhibitory relationship exists between this system and the system we use to think about physical mechanisms.

The genuine problem of consciousness is a problem about explanation, but it isn’t the sort of problem that can be solved by a theory of consciousness. We have two different ways of understanding the mind: we can understand it as a physical mechanism, and we can understand it from a personal perspective. The problem is that contemporary scientific psychology aims almost exclusively at mechanistic explanations of the mind. This is, ironically, no less true of most supposed scientific theories of consciousness than it is of the regular business of experimental psychology and cognitive neuroscience. Yet, for reasons both intellectual and practical, mechanistic explanation is not enough on its own. We can’t understand the mind unless we can understand it for ourselves, from our own personal-level perspective. If we are right that physical and phenomenal concepts belong to fundamentally distinct networks, then it is a problem that may never be definitively resolved. Nonetheless, it is a problem we can make progress on, for even if these networks always remain distinct, they can still be integrated into a more coherent whole. The genuine problem of consciousness is the challenge of achieving this largescale integration of our conceptual scheme.
See Jack's website for responses to and commentaries on this paper.

Paradoxes Of Our Age

I don't usually inflict homilies on my readers, but I pass on these brief lines found while cruising the web, attributed to the 14th Dali Lama.

We have bigger houses but smaller families;

More conveniences, but less time.

We have more degrees but less sense.

More knowledge but less judgment.


More experts, but more problems.


More medicines but less healthiness.


We’ve been all the way to the moon and back, but have trouble in crossing the street to meet our new neighbor.


We build more computers to hold more copies than ever, but have less real communication;


We have become long on quantity, but short on quality.


These are times of fast foods but slow digestion.


Tall men but short characters.


Steep profits but shallow relationships.


It’s a time when there is much in the window, but nothing in the room.


Thursday, July 26, 2007

Our baseline brain activity alters conscious perception

Our perceptions of weak somatosensory (touching) stimuli can vary widely. Boly et al. (PDF here) ask whether variability in perception of identical stimuli relates to differences in prestimulus, baseline brain activity. Here is their abstract, followed by one figure from their paper:

In perceptual experiments, within-individual fluctuations in perception are observed across multiple presentations of the same stimuli, a phenomenon that remains only partially understood. Here, by means of thulium–yttrium/aluminum–garnet laser and event-related functional MRI, we tested whether variability in perception of identical stimuli relates to differences in prestimulus, baseline brain activity. Results indicate a positive relationship between conscious perception of low-intensity somatosensory stimuli and immediately preceding levels of baseline activity in medial thalamus and the lateral frontoparietal network, respectively, which are thought to relate to vigilance and "external monitoring." Conversely, there was a negative correlation between subsequent reporting of conscious perception and baseline activity in a set of regions encompassing posterior cingulate/precuneus and temporoparietal cortices, possibly relating to introspection and self-oriented processes. At nociceptive levels of stimulation, pain-intensity ratings positively correlated with baseline fluctuations in anterior cingulate cortex in an area known to be involved in the affective dimension of pain. These results suggest that baseline brain-activity fluctuations may profoundly modify our conscious perception of the external world.

Neural correlates of somatosensory stimuli awareness. Consciously perceived stimuli compared with unperceived intensity-matched stimuli were associated with greater activity in bilateral dorsolateral prefrontal (DLPF) and intraparietal sulcus/posterior parietal cortex (IPS) activity (yellow-red sections) (A) and less activity in a network encompassing bilateral posterior cingulate precuneas (Pr), mesiofrontal cortices (MF), temporoparietal junctions (TP), right inferior temporal (IT), and left superior frontal gyri (SF) (blue sections) (B).

Obesity as contagion

Here are some clips from a rather fascinating article by Kolata in the NYTimes. We know that moods are like viruses, contagious - one happy person can lift the mood of the group they are in, one depressed person can do the opposite. Such a process appears to operate on a much longer time scale with respect to body mass. (By the way, I draft this post on Wednesday afternoon and later at happy hour at Genna's bar on Capitol square in Madison, I look up at the NBC evening news to find the material featured there. The marketing of sexy new findings moves very fast).

The Framingham study involved a detailed analysis of a large social network of 12,067 people who had been closely followed for 32 years, from 1971 until 2003. The investigators knew who was friends with whom, as well as who was a spouse or sibling or neighbor, and they knew how much each person weighed at various times over three decades. That let them examine what happened over the years as some individuals became obese. Did their friends also become obese? Did family members or neighbors?...The answer, the researchers report, was that people were most likely to become obese when a friend became obese. That increased a person’s chances of becoming obese by 57 percent....Proximity did not seem to matter: the influence of the friend remained even if the friend was hundreds of miles away. And the greatest influence of all was between mutual close friends. There, if one became obese, the odds of the other becoming obese were nearly tripled...You change your idea of what is an acceptable body type by looking at the people around you.

Wednesday, July 25, 2007

fMRI of "Love"

Wow, count on some scientists to take all the titilation out of it with a title like:
"The Neural Basis of Love as a Subliminal Prime: An Event-related Functional Magnetic Resonance Imaging Study." Here is the abstract from Ortigue et al.:

Throughout the ages, love has been defined as a motivated and goal-directed mechanism with explicit and implicit mechanisms. Recent evidence demonstrated that the explicit representation of love recruits subcorticocortical pathways mediating reward, emotion, and motivation systems. However, the neural basis of the implicit (unconscious) representation of love remains unknown. To assess this question, we combined event-related functional magnetic resonance imaging (fMRI) with a behavioral subliminal priming paradigm embedded in a lexical decision task. In this task, the name of either a beloved partner, a neutral friend, or a passionate hobby was subliminally presented before a target stimulus (word, nonword, or blank), and participants were required to decide if the target was a word or not. Behavioral results showed that subliminal presentation of either a beloved's name (love prime) or a passion descriptor (passion prime) enhanced reaction times in a similar fashion. Subliminal presentation of a friend's name (friend prime) did not show any beneficial effects. Functional results showed that subliminal priming with a beloved's name (as opposed to either a friend's name or a passion descriptor) specifically recruited brain areas involved in abstract representations of others and the self, in addition to motivation circuits shared with other sources of passion. More precisely, love primes recruited the fusiform and angular gyri. Our findings suggest that love, as a subliminal prime, involves a specific neural network that surpasses a dopaminergic–motivation system.

Coordinated eye movements during dialog.

A commentary on an interesting article by Richardson et al. which illustrates yet again the social synchrony of our brains. See also this PsyBlog link on our nonverbal symphony and synchrony of interactions, as well as this previous post on an EEG signal that reflects social coordination. Or, this link on social context reflected at the level of single cell recordings in the monkey parietal cortex.

A dialogue, though generally understood to be a conversation between two people, allows for much more than the mere exchange of verbal information. Linguistic (for example, syntax) and nonlinguistic (for example, body postures) tell-tales develop and become synchronized as people talk and listen. Visual attention is another dimension in which behavior can become coordinated as when a listener's gaze is directed toward an object of mutual interest by pointing.

Richardson et al. show that the eyes of conversants--who are looking at the same scene but are not within sight of each other--tracked the same objects within the scene for several seconds, starting from the time at which the speaker began to fixate on the object before talking about it and including the time taken by the listener to saccade to the object after hearing what the speaker had begun to say. Another important contribution to the coordination of visual attention comes from having a common ground of understanding. Conversants looking at a Salvador Dalí painting were more likely to exhibit synchronized eye movements if they had previously heard the same introduction, either to the painting itself or to Dalí's life, as compared to pairs of conversants in which one had heard about the painting and the other about his life.

Tuesday, July 24, 2007

Neuroeconomics - a site to browse

I thought I would point you to the website of Read Montaque's Human Neuroimaging Laboratory at Baylor University. He is is guy whose work on behavioral preference for culturally familiar drinks is credited with a large part of the responsibility for the current neuromarketing craze. A new direction is the hyperscanning method by which multiple subjects, each in a separate MRI scanner, can interact with one another while their brains are simultaneously scanned. This permits study of the brain responses that underlie important social interactions.

Mild stress during pregnancy increases risk of subsequent brain lesions

I'm passing on this work from Rangon et al. Not exactly a friendly abstract, but it gets the message across:

Cerebral palsy remains a public health priority. Recognition of factors of susceptibility to perinatal brain lesions is key for the prevention of cerebral palsy. In most cases, the pathophysiology of these lesions is thought to involve prior exposure to predisposing factors that make the developing brain more vulnerable to perinatal events. The present study tested the hypothesis that exposure to chronic minimal stress throughout gestation would sensitize the offspring to neonatal excitotoxic brain lesions, which mimic lesions observed in cerebral palsy. Pregnant mice were exposed to chronic, ultramild stress, applied throughout gestation. Neonatal brain lesions were induced by intracerebral injection of glutamate analogs. Excitotoxic lesions were significantly worsened in pups exposed to gestational stress. Stress induced a significant rise of circulating corticosterone levels both in pregnant mothers and in newborn pups. The deleterious effects of stress on excitotoxicity were totally suppressed in mice with reduced levels of glucocorticoid receptors. Stress induced a significant increase of neopallial NMDA binding sites in the offspring. At adulthood, animals exposed to stress and neonatal excitotoxic challenge showed a significant impairment in the Morris water maze test when compared with animals exposed to the excitotoxic challenge but not the gestational stress. These findings suggest that stress during gestation, which may mimic low-level stress in human pregnancy, could be a novel risk factor for cerebral palsy.

Monday, July 23, 2007

dericbownds.net - new website design

My website apart from this blog has been an evolutionary accretion of my amateur code done over many years, kind of a mess. Also a confusion of professional and personal stuff. Having received comments on how much more coherent the blog design was (a professional template, provided by blogger), I've enlisted the assistance of a friend and internet consultant, Kelly Doering, to clean up the act. You might have a look at the new product.

Novel environments stimulate memory molecules

Remembering something requires changes in how our nerve cells talk to each other, and a process called long termed potentiation, or LTP, is regarded as a good model for one such underlying change. LTP refers to an enhancement of the synapse between two nerve cells such that an action potential arriving in a presynaptic terminal causes a larger voltage change in the postsynaptic terminal. This process is thought to require the synthesis of new proteins in the synapse and is essential in establishing long term memories(LTM). Moncada and Viola have made the interesting observation that weak inhibitory avoidance training, which induces short- but not long-term memory (LTM), can be consolidated into LTM by an exploration to a novel, but not a familiar, environment occurring close in time to the training session. "This memory-promoting effect caused by novelty depends on activation of dopamine D1/D5 receptors and requires newly synthesized proteins in the dorsal hippocampus. The results indicate the existence of a behavioral tagging process in which the exploration to a novel environment provides the plasticity-related proteins to stabilize the inhibitory avoidance memory trace."

Imperceptible cross modal stimuli produce percepts.

A brief review by Chapman notes that Ramos-Estebanez et al. have done an intriguing experiment involving visuotactile interactions, asking whether subthreshold sensory stimulation can sum across modalities to produce a reportable percept. Some clips from the review and the original article:

The study combined transcranial magnetic stimulation (TMS) to V1 with peripheral electrical stimulation (PES) to the left and right index fingers. For many subjects, TMS at sufficient magnitude directly over V1 evokes phosphenes, spots or "sparks" of light in the visual field that do not correlate with any external stimulus.

Figure. Test conditions used in the experiment in conjunction to TMS delivered to the occipital cortex. PES was delivered in conjunction with occipital TMS at varying ISIs (40, 60, 80, and 100 ms) to either the right or left hand and with the hands in the uncrossed or crossed position.


TMS and PES levels were set at 80% of the threshold stimulation intensity. Subthreshold TMS to left V1 produced phosphene perceptions in ~10% of trials. When subthreshold PES to the left hand was added to TMS, there was no significant change in phosphene perception. However, when PES to the right hand was combined with TMS, a dramatic effect emerged: subjects suddenly reported phosphene perceptions up to 50% of trials. This result suggests that the two imperceptible stimuli combine across modalities to produce a salient percept. At no point did the subjects experience reportable sensations in either hand. The striking effect of stimulation to the right hand persisted whether the hands were crossed or uncrossed. This is what one might expect from "hardwired" connections between the right side of the body and unimodal areas representing the right visual hemifield.

These experiments supplement previous work by showing that even subthreshold sensory stimuli can combine across modalities and that the time course of this interaction occurs within an early, specific temporal range. Many questions remain, because the physiological and anatomical underpinnings of early crossmodal interactions are still being uncovered. However, as our understanding of crossmodal interactions evolves, studies such as these may gradually reshape our current concept of brain organization.

Friday, July 20, 2007

Irritating Images

A 'random sample' from a recent Science Magazine, on Art that Jars:

Some images are literally eyesores. Scientists have long known that the wrong mix of shapes and colors can cause discomfort, headaches, or even seizures. Now, they're starting to figure out why.

Psychologist Arnold Wilkins of the University of Essex, U.K., and artist Debbie Ayles--who creates paintings inspired by her migraines (such as the one shown here)--used a Sciart grant from the Wellcome Trust to tease out the keys to annoying art. Focus groups at an exhibition of Ayles's work last year helped identify narrow stripes and juxtaposed complementary colors as inducers of discomfort. Wilkins then compared the subjective ratings of a variety of paintings with each picture's energy intensity, measured by Fourier analysis of stripes' spatial frequency.

At a talk in Cambridge, U.K., last week, Wilkins said the pictures the focus groups found unpleasant featured vertical stripes at the width that we're visually most sensitive to--about 3 stripes per degree of the visual field (a finger held at arm's length corresponds to about 1 degree). The stripe factor applies to type fonts, too--letter length and thickness make Times New Roman a slower read than Verdana, says Wilkins. He says his results can be applied to design, from picking an optimal type size and font for children's books to choosing public murals.

Suppression of emotional memories.

Here is the abstract from Depre et al.'s article (PDF here):

Whether memories can be suppressed has been a controversial issue in psychology and cognitive neuroscience for decades. We found evidence that emotional memories are suppressed via two time-differentiated neural mechanisms: (i) an initial suppression by the right inferior frontal gyrus over regions supporting sensory components of the memory representation (visual cortex, thalamus), followed by (ii) right medial frontal gyrus control over regions supporting multimodal and emotional components of the memory representation (hippocampus, amygdala), both of which are influenced by fronto-polar regions. These results indicate that memory suppression does occur and, at least in nonpsychiatric populations, is under the control of prefrontal regions.
They used used a Think/No-Think paradigm (T/NT) in which individuals attempt to elaborate a memory by repetitively thinking of it (T condition) or to suppress a memory by repetitively not letting it enter consciousness (NT condition).
Fig. 1. (A) Experimental procedure. Individuals were first trained during structural scanning to associate 40 cue-target pairs. During the experimental phase, brain activity was recorded using fMRI while individuals viewed only the face (16 faces per condition, 12 repetitions per face; 3.5 s per face). On some trials they were instructed to think of the previously learned picture; on other trials they were instructed not to let the previously associated picture enter consciousness. The presentation of only the cue (i.e., the face) ensures that individuals manipulate the memory of the target picture. The additional faces (8 items) not shown during this phase acted as a behavioral baseline. During the test phase, the individuals were shown the 40 faces and asked to describe the previously associated picture. (B) Behavioral results: percentage recall for each participant for T trials (green) and NT trials (red), with the dotted line indicating baseline recall for items not viewed in the experimental phase.

Fig. 2. Functional activation of brain areas involved in (A) cognitive control, (B) sensory representations of memory, and (C) memory processes and emotional components of memory (rSFG, right superior frontal gyrus; rMFG, right middle frontal gyrus; rIFG, right inferior frontal gyrus; Pul, pulvinar; FG, fusiform gyrus; Hip, hippocampus; Amy, amygdala). Red indicates greater activity for NT trials than for T trials; blue indicates the reverse. Conjunction analyses revealed that areas seen in blue are the culmination of increased activity for T trials above baseline as well as decreased activity of NT trials below baseline.
Here is the last portion of their discussion:
At a broader level, our findings extend research suggesting that prefrontal brain areas associated with inhibitory mechanisms (BA 10 and superior, inferior, and middle FG) are lateralized predominantly to the right hemisphere. We have shown the involvement of these areas in the suppression of emotional memories, which replicates current literature suggesting that these areas are active in the suppression of emotional reactivity. Activity in these brain areas, along with inhibition over Hip and Amy, suggests that suppression of emotional memories may use mechanisms similar to those used in emotion regulation. Thus, various right-lateralized PFC areas may be involved in coordinating suppression processes across many behavioral domains, including memory retrieval, motor processes, feelings of social rejection, self motives, and state emotional reactivity.

Our findings may have implications for therapeutic approaches to disorders involving the inability to suppress emotionally distressing memories and thoughts, including PTSD, phobias, ruminative depression/anxiety, and OCD. They provide the possibility for approaches to controlling memories by suppressing sensory aspects of memory and/or by strengthening cognitive control over memory and emotional processes through repeated practice. Refinement of therapeutic procedures based on these distinct means of manipulating emotional memory might be an exciting and fruitful development in future clinical research.

Our results suggest that effective voluntary suppression of emotional memory only develops with repeated attempts to cognitively control posterior brain areas underlying instantiated memories. In this sense, memory suppression may best be conceived as a dynamic process in which the brain acquires multiple modulatory influences to reduce the likelihood of retrieving unwanted memories.

Thursday, July 19, 2007

Remembering small pattern differences.

Bannerman and Sprengel discuss (PDF here) and offer perspective on work of McHugh et al. from Tonegawa's laboratory showing synaptic details of how the mouse hippocampus carries out pattern separation. The findings explain how we detect small changes in our environment, perhaps allowing us to update and guide our choices. They offer a nice graphic of the hippocampus, which is central in this processes.

Knowing what, when, and where. In the mouse brain, the dentate gyrus region of the hippocampus can detect small changes in the animal's spatial environment and differentiate between recent experiences that occur in the same place. The white arrows trace a path of signaling between different regions of the hippocampus. Sensory information can enter the hippocampus from the entorhinal cortex and is sent back to the entorhinal cortex after processing.

Can Systems Biology integrate Chinese and Western Meidicine?

Here is the PDF of an interesting article by Jane Qui that I pass on in part because I have been struck by the number of emails I have received from readers of this blog asking questions about alternative medicine and cures (a subject on which I an NOT an expert). The article addresses the question of whether a formidable gap can be addressed:

Modern Western medicine generally prescribes treatments for specific diseases, often on the basis of their physiological cause. Traditional Chinese medicine, however, focuses on symptoms, and uses plant and animal products, minerals, acupuncture and moxibustion — the burning of the mugwort herb (Artemisia vulgaris) on or near the skin. But whether these methods are effective and, if they are, how they work remain a source of some derision. The greatest divide is in the testing. In the West, researchers test a drug's safety and efficacy in randomized, controlled trials. Traditional Chinese treatments are mixtures of ingredients, concocted on the spot on the basis of a patient's symptoms and characteristics and using theories passed down through generations.
The article discusses how researchers in China and elsewhere, meanwhile, are advocating systems biology — the study of the interactions between proteins, genes, metabolites and components of cells or organisms — as a way to assess the usefulness of traditional medicines.

Wednesday, July 18, 2007

Attentional expertise in long-term meditators: neural correlates

More from Richie Davidson's laboratory here at Wisconsin. The article is open-access, you can go there for the graphics:

Meditation refers to a family of mental training practices that are designed to familiarize the practitioner with specific types of mental processes. One of the most basic forms of meditation is concentration meditation, in which sustained attention is focused on an object such as a small visual stimulus or the breath. In age-matched participants, using functional MRI, we found that activation in a network of brain regions typically involved in sustained attention showed an inverted u-shaped curve in which expert meditators (EMs) with an average of 19,000 h of practice had more activation than novices, but EMs with an average of 44,000 h had less activation. In response to distracter sounds used to probe the meditation, EMs vs. novices had less brain activation in regions related to discursive thoughts and emotions and more activation in regions related to response inhibition and attention. Correlation with hours of practice suggests possible plasticity in these mechanisms.

Internet connectivity model

Don't ask me what k-shell decomposition is, but Carmi et al. (PDF here) perform an analysis of the internet using it to yield an interesting model of internet connectivity and a summary graphic. Analysis of this sort is also applied to brain networks. Their abstract, followed by the graphic:

We study a map of the Internet (at the autonomous systems level), by introducing and using the method of k-shell decomposition and the methods of percolation theory and fractal geometry, to find a model for the structure of the Internet. In particular, our analysis uses information on the connectivity of the network shells to separate, in a unique (no parameters) way, the Internet into three subcomponents: (i) a nucleus that is a small ({approx}100 nodes), very well connected globally distributed subgraph; (ii) a fractal subcomponent that is able to connect the bulk of the Internet without congesting the nucleus, with self-similar properties and critical exponents predicted from percolation theory; and (iii) dendrite-like structures, usually isolated nodes that are connected to the rest of the network through the nucleus only. We show that our method of decomposition is robust and provides insight into the underlying structure of the Internet and its functional consequences. Our approach of decomposing the network is general and also useful when studying other complex networks.

Visualization of our data of the Internet at the AS level. (Upper) A plot of all nodes, ordered by their k-shell indices, using the program of ref. 13. The legend to the left denotes degree, and the legend to the right denotes k-shell index. (Lower) A schematic plot of the suggested Medusa model decomposition of the AS level Internet into three components.

Tuesday, July 17, 2007

Thoughts on, reservations about, science blogging...

I've just had a brief exchange with David Dobbs, who wrote the piece on Williams Syndrome mentioned a few posts back. He has decided to cut back on blogging, and I found his comments on this, and a reaction to comments by Andrew Sullivan, worth passing on. The mindsets of blogging and book writing are very different. (And...the reason I haven't gone beyond very preliminary efforts to do a second version of my "Biology of Mind" book.)

Whole brain structural networks - some neat movies

Hagmann et al propose that diffusion MRI provides an efficient methodology to generate large, comprehensive and individual white matter connectional datasets of the living or dead, human or animal brain. This non-invasive tool enables study of the basic and potentially complex network properties of the entire brain. For two human subjects they find that their individual brain networks have an exponential node degree distribution and that their global organization is in the form of a small world. The link to their article takes you to three fascinating movies: one showing whole brain tractography, a second showing partition of the white-gray matter interface into approximately 1000 regions of interest, and the third, included here via YouTube so you don't have to download the quicktime movie, showing connections between different visual areas.

A musical interlude...

I put my playing of a Debussy Reverie on YouTube about 10 months ago, and am completely amazed that it has by now had ~18,000 viewings, and over 50 largely constructive comments, many of which suggested to "slow down." So, I did a second version and posted it two months ago, which I pass on here. Response has been more favorable.

Genetics and tonal languages

It is likely that there are heritable differences of brain structure and function that affect language acquisition and usage...cognitive biases in a population of acquirers could influence the direction of language change across generations. These biasing effects could result in linguistic differences between populations, producing nonspurious (causal) correlations between genetic and linguistic diversities. Dediu and Ladd:

... propose that the linguistic typology of tone is affected by such a bias. Human languages differ typologically in the way they use voice fundamental frequency (pitch). All languages use consonants and vowels to distinguish one word or grammatical category from another, but, in addition, so-called "tone languages" (e.g., Chinese) use pitch for this purpose as well, whereas "non-tone languages" (e.g., English) use pitch only at sentence level (to convey emphasis, emotion, etc.). In tone languages, that is, pitch is organized into tone phonemes that are functionally comparable with consonant and vowel phonemes. Tone languages are the norm in sub-Saharan Africa and are very common in continental and insular southeast Asia. They are rare in the rest of Eurasia, North Africa, and Australia. They are relatively common in Central America, the Caribbean, and the Amazon basin, and occur sporadically elsewhere among the aboriginal languages of the Americas..
Here is their Abstract:
The correlations between interpopulation genetic and linguistic diversities are mostly noncausal (spurious), being due to historical processes and geographical factors that shape them in similar ways. Studies of such correlations usually consider allele frequencies and linguistic groupings (dialects, languages, linguistic families or phyla), sometimes controlling for geographic, topographic, or ecological factors. Here, we consider the relation between allele frequencies and linguistic typological features. Specifically, we focus on the derived haplogroups (note: these are sets of nucleotide polymorphisms) of the brain growth and development-related genes ASPM and Microcephalin, which show signs of natural selection and a marked geographic structure, and on linguistic tone, the use of voice pitch to convey lexical or grammatical distinctions. We hypothesize that there is a relationship between the population frequency of these two alleles and the presence of linguistic tone and test this hypothesis relative to a large database (983 alleles and 26 linguistic features in 49 populations), showing that it is not due to the usual explanatory factors represented by geography and history. The relationship between genetic and linguistic diversity in this case may be causal: certain alleles can bias language acquisition or processing and thereby influence the trajectory of language change through iterated cultural transmission.

Monday, July 16, 2007

Most popular consciousness papers for June 2007

That is, the five most downloaded from the eprint archive maintained by the Association for the Scientific Study of Consciousness.

1. Rosen, Alan and Rosen, David B. (2006) The Design of a
Sensation-generating Mechanism in the Brain: A first step towards a
quantitative definition of consciousness. In: Consciousness and
Cognition (1223 downloads from 9 countries).
http://eprints.assc.caltech.edu/195/

2. Sagiv, Noam and Ward, Jamie (2006) Crossmodal interactions: lessons
from synesthesia. In: Visual Perception, Part 2 (1171 downloads from
20 countries). http://eprints.assc.caltech.edu/224/

3. Ruby, Perrine and Legrand, Dorothée (2007) Neuroimaging the self?
In: Sensorimotor foundations of higher cognition. OUP (882 downloads
from 14 countries). http://eprints.assc.caltech.edu/275/

4. Koriat, A. (2006) Metacognition and Consciousness. In: Cambridge
handbook of consciousness. CUP (804 downloads from 15 countries).
http://eprints.assc.caltech.edu/175/

5. Windt, Jennifer Michelle and Metzinger, Thomas (2006) The
philosophy of dreaming and self-consciousness: What happens to the
experiential subject during the dream state? In: The new science of
dreaming (780 downloads from 22 countries).
http://eprints.assc.caltech.edu/200/

Modulating emotional appraisal by false physiological feedback.

Grey et al. examine how emotional appraisal is influenced by physiological feedback. Their observations make me wonder whether trying the opposite trick, giving false feedback that suggests less autonomic arousal, could chill out reactions to an emotional stimulus... Their main points:

James and Lange proposed that emotions are the perception of physiological reactions. Two-level theories of emotion extend this model to suggest that cognitive interpretations of physiological changes shape self-reported emotions. Correspondingly false physiological feedback of evoked or tonic bodily responses can alter emotional attributions. Moreover, anxiety states are proposed to arise from detection of mismatch between actual and anticipated states of physiological arousal. However, the neural underpinnings of these phenomena previously have not been examined.

We undertook a functional brain imaging (fMRI) experiment to investigate how both primary and second-order levels of physiological (viscerosensory) representation impact on the processing of external emotional cues. Twelve participants were scanned while judging face stimuli during both exercise and non-exercise conditions in the context of true and false auditory feedback of tonic heart rate. We observed that the perceived emotional intensity/salience of neutral faces was enhanced by false feedback of increased heart rate. Regional changes in neural activity corresponding to this behavioural interaction were observed within included right anterior insula, bilateral mid insula, and amygdala. In addition, right anterior insula activity was enhanced during by asynchronous relative to synchronous cardiac feedback even with no change in perceived or actual heart rate suggesting this region serves as a comparator to detect physiological mismatches. Finally, BOLD activity within right anterior insula and amygdala predicted the corresponding changes in perceived intensity ratings at both a group and an individual level.

Our findings identify the neural substrates supporting behavioural effects of false physiological feedback, and highlight mechanisms that underlie subjective anxiety states, including the importance of the right anterior insula in guiding second-order “cognitive” representations of bodily arousal state.

Williams Syndrome - evidence for a discrete social brain

David Dobbs offers a very well written essay (PDF here) on Williams Syndrome in the Sunday New York Times Magazine (7/8/07). The syndrome is caused by a well-defined deletion in chromosome 7 that occasionally occurs during the synthesis of egg or sperm cells. Patients have a low IQ (~60) and compromised spatial skill and analytical thought, but are hyper-sociable and friendly, very talkative. An pathway from the orbitofrontal (OFC) cortex to the amygdala that usually signals dangerous or angry faces is inactive; but curiously the OFC-amygdala connection still works normally for nonsocial threats such as pictures of snakes, sharks or car crashes. The existence of this syndrome provides perhaps the strongest evidence for genetically and developmentally distinct class of 'social brain' mechanisms distinct from other higher sensory, motor, and analytical skills.

Sunday, July 15, 2007

A Sunday Walk....

Around my house on Twin Valley Road in Town of Middleton, Wisconsin. (It is a stone schoolhouse built in 1860, converted to a residence).





Friday, July 13, 2007

How pain preempts cognition - and about itching

I found these two articles on pain and itching interesting, particularly since I've been going through an orgy of both after exposing myself to poison oak or ivy while working in the yard. Bingel et al. show some brain correlates of why I found it difficult to focus on normal cognitive activities during this period:

It is well known that pain attracts attention and interferes with cognition. Given that the mechanisms behind this phenomenon are largely unknown, we used functional magnetic resonance imaging and presented visual objects with or without concomitant pain stimuli. To test for the specificity of pain, we compared this modulatory effect with a previously established modulatory effect of working memory on visual object processing. Our data showed a comparable behavioral effect of both types of modulation and identified the lateral occipital complex (LOC) as the site of modulation in the ventral visual stream, for both pain and working memory. However, the sources of these modulatory effects differed for the two processes. Whereas the source of modulation for working memory could be attributed to the parietal cortex, the modulatory effect of pain was observed in the rostral anterior cingulate cortex (rACC), an area ideally suited to link pain perception and attentional control.
A) fMRI effects of the interaction of background visibility with working memory load were observed in bilateral LOC, reflecting a phasic modulation of LOC activity.
(B) Corresponding activation and parameter estimates related to the interaction of Pain × Visibility.

Now, on to itching (also central to my poison oak story, still going on....). Johanek et al. note a curious distinction between histamine induced itching and itching caused by cutaneous application of spicules from the cowhage plant. They show a different class of afferent C-fiber afferents signaling non-histamine induced itching:
The neuronal pathways for itch have been characterized mainly based on responses to histamine. Intracutaneous application of histamine produces intense itch and a large area of axon-reflexive vasodilation ("flare") around the application site. Both phenomena are thought to be mediated through neuronal activity in itch-specific, mechanoinsensitive C-fiber afferents (CMi). However, mechanical and electrical stimuli that do not activate CMi fibers can cause the sensation of itch, and itch may occur without flare, suggesting that other neuronal itch pathways exist. Because cutaneous application of spicules from the plant Mucuna pruriens (cowhage) has been anecdotally reported to produce itch without flare, we performed psychophysical experiments to investigate whether the mechanisms underlying cowhage- and histamine-induced itch differ. Although histamine and cowhage produced itch of similar magnitude, the itch to cowhage was not correlated with the itch to histamine; some subjects had intense itch to cowhage and little itch to histamine and visa versa. Laser Doppler measurements of blood flow revealed that histamine led to a large area of vasodilation, whereas cowhage produced vasodilation restricted to the application site. Pretreatment of the skin with an antihistamine blocked the itch produced by histamine but did not prevent cowhage-induced itch. Desensitization of the skin with topical capsaicin abolished cowhage-induced itch but did not significantly alter histamine-induced itch. These findings indicate that cowhage itch is signaled through a population of capsaicin-sensitive afferent nerve fibers that is distinct from CMi fibers mediating histamine-induced itch. Cowhage may be useful to investigate the neural pathway mediating nonhistaminergic itch.

Negative suggestions enhancing pain -an antidote?

Benedetti et al. provide an interesting review of the nocebo effect (the anticipation of pain enhancing its magnitude). This is the opposite of the placebo effect, where a more positive expectation can lower perceived pain. Their article (PDF here) provides some interesting graphics of brain imagining showing this effect, and discusses relevant brain receptors.
Recent experimental evidence indicates that negative verbal suggestions induce anticipatory anxiety about the impending pain increase, and this verbally-induced anxiety triggers the activation of cholecystokinin (CCK) which, in turn, facilitates pain transmission. CCK-antagonists have been found to block this anxiety-induced hyperalgesia, thus opening up the possibility of new therapeutic strategies whenever pain has an important anxiety component.

Thursday, July 12, 2007

Rodent Altruism - Lending an Anonymous Paw

Krista Zala writes a nice summary of work by Rutte and Taborsky. Some clips:

Rats given a helping paw are more prone to helping others--even complete strangers. This suggests that the animals' social life may be richer than we thought...Many animals, including rats, demonstrate direct reciprocity--described as "I'll help you if you help me." But generalized reciprocity, in which individuals remember how they were treated in the recent past and apply it to others, including strangers, has been thought to be a uniquely human trait...However, previous studies haven't specifically looked for generalized reciprocity in other animals.



To find out if rats have this capacity, Rutte and Michael Taborsky of the University of Bern in Switzerland trained rats to pull a lever that would deliver an oat flake reward to another rat on the other side of a wire mesh wall in a shared cage. Some of these rats were then put on the receiving side, paired for several days with either other rats trained to be helpful—-three different ones over the span--or with untrained rats that didn't pull the lever and provide food. After several days of living with such generous or not-so-generous neighbors, these test rats were then switched back to the lever side of the cage, paired with a new neighbor rat, and watched to see if they would provide food for it. Rats who had been paired with food-providing neighbors helped their new partner more often than those who had had unhelpful neighbors. Rutte's team also found that when a test rat was paired with one of the rats that had earlier provided it with oak flakes, it pulled the food lever even more--showing direct reciprocity. When the cage was empty of any neighbor rat, it barely pulled the food lever at all.

In a pack of 200 rats, where it's hard to remember who's been helpful and who hasn't, a general willingness to help others makes sense as a strategy...It may be a mechanism for how cooperation can evolve when you cannot recognize your partner...rats are notoriously bad at remembering other individuals.

Looking into the prevalence of generalized reciprocity among social and nonsocial animals may help our understanding of the evolution of cooperation.
The New York Times Science section has now also done a popular summary of this work (PDF here), and the graphic above is from that review.

Altruistic Chimps and Children

As a companion to the blog posting on helping rodents, this work from Tomasello's laboratory. The article has some nice videos. Here is the author's summary:

Debates about altruism are often based on the assumption that it is either unique to humans or else the human version differs from that of other animals in important ways. Thus, only humans are supposed to act on behalf of others, even toward genetically unrelated individuals, without personal gain, at a cost to themselves. Studies investigating such behaviors in nonhuman primates, especially our close relative the chimpanzee, form an important contribution to this debate. Here we present experimental evidence that chimpanzees act altruistically toward genetically unrelated conspecifics. In addition, in two comparative experiments, we found that both chimpanzees and human infants helped altruistically, regardless of any expectation of reward, even when some effort was required, and even when the recipient was an unfamiliar individual—all features previously thought to be unique to humans. The evolutionary roots of human altruism may thus go deeper than previously thought, reaching as far back as the last common ancestor of humans and chimpanzees.

Wednesday, July 11, 2007

Neuroimaging of emotions driving political strategy...

My October 23 post mentioned the work of Westen, who has used functional neuroimaging to show how emotions prevail over reason when people rationalize their political choices. This material - up to date neuroscience of decision making - has been taken up and absorbed as a guide to campaign strategy in an amazingly short time, with democratic party strategists particularly engaged by Westen's recent book, “The Political Brain: The Role of Emotion in Deciding the Fate of the Nation” (Public Affairs).

Westen takes the unlikely position that the Democratic Party should, for the most part, forget about issues, policies, even facts, and instead focus on feelings. His book takes a very different tack than, say, “What’s the Matter With Kansas?” by Thomas Frank or Al Gore’s “Assault on Reason,” which try to explain voter behavior in terms of self-interest and factual analysis.

The recent review of Westen's book by Patricia Cohen in the New York Times, notes that Westen has by now given numerous talks to political groups and set up a political consulting company. She notes Bill Clinton's positive reaction to the book, as he "particularly liked the discussion of how one could evoke emotion without being intellectually dishonest.” Cohen's review is worth reading (PDF here).

In this vein, it is interesting that Louis Menand in a recent New Yorker review titled "The Fractured Franchise" has an elegant discussion of evidence that most voters are massively ignorant and misinformed about political reality (PDF here). Thus, even when 'democracy works' the results can be a disaster. (So we should prefer rule by economists?) He reviews the recent book by Bryan Caplan, “The Myth of the Rational Voter: Why Democracies Choose Bad Politics” (Princeton; $29.95). (By the way, see also Menand's earlier article "The Unpolitical Animal." He is a brilliant guy. )

Hi-Tech fMRI lie detection - another scam?

Margaret Talbot writes an interesting article in The New Yorker (PDF here) about the current hype over lie detection using brain scanning techniques, and the sprouting of numerous companies wanting to sell their services to private investigators, police departments, U.S. and foreign government agencies, etc. The article is a broad discussion of lie detection also by other physiological indicators such as skin conductance and blood pressure. Most interesting to me were the critical points raised. Here are a few clips from the article:

Paul Bloom, a cognitive psychologist at Yale, believes that brain imaging has a beguiling appeal beyond its actual power to explain mental and emotional states. "Psychologists can be heard grousing that the only way to publish in Science or Nature is with pretty color pictures of the brain," he wrote in an essay for the magazine Seed. "Critical funding decisions, precious column inches, tenure posts, science credibility, and the popular imagination have all been influenced by fMRI's seductive but deceptive grasp on our attentions." Indeed, in the past decade, Nature alone has published nearly a hundred articles involving fMRI scans. The technology is a remarkable tool for exploring the brain, and may one day help scientists understand much more about cognition and emotion. But enthusiasm for brain scans leads people to overestimate the accuracy with which they can pinpoint the sources of complex things like love or altruism, let alone explain them.

Brain scans enthrall us, in part, because they seem more like "real" science than those elaborate deductive experiments that so many psychologists perform. In the same way that an X-ray confirms a bone fissure, a brain scan seems to offer an objective measure of mental activity. And, as Bloom writes, fMRI research "has all the trappings of work with great lab-cred: big, expensive, and potentially dangerous machines, hospitals and medical centers, and a lot of people in white coats."

Deena Skolnick Weisberg, a graduate student at Yale, has conducted a clever study, to be published in the Journal of Cognitive Neuroscience, which points to the outsized glamour of brain-scan research. She and her colleagues provided three groups--neuroscientists, neuroscience students, and ordinary adults--with explanations for common psychological phenomena (such as the tendency to assume that other people know the same things we do). Some of these explanations were crafted to be bad. Weisberg found that all three groups were adept at identifying the bad explanations, except when she inserted the words "Brain scans indicate." Then the students and the regular adults became notably less discerning. Weisberg and her colleagues conclude, "People seem all too ready to accept explanations that allude to neuroscience."

Nancy Kanwisher, a cognitive scientist at M.I.T., relies a great deal on MRI technology. In 1997, she identified an area near the bottom of the brain that is specifically involved in perceiving faces. She has become a pointed critic of the rush to commercialize brain imaging for lie detection, and believes that it's an exaggeration even to say that research into the subject is "preliminary." The tests that have been done, she argues, don't really look at lying. "Making a false response when instructed to do so is not a lie," she says. The ninety-per-cent "accuracy" ascribed to fMRI lie detection refers to a scenario so artificial that it is nearly meaningless. To know whether the technology works, she believes, "you'd have to test it on people whose guilt or innocence hasn't yet been determined, who believe the scan will reveal their guilt or innocence, and whose guilt or innocence can be established by other means afterward." In other words, you'd have to run a legal version of a clinical trial, using real suspects instead of volunteers.

She points out that the various brain regions that appear to be significantly active during lying are "famous for being activated in a wide range of different conditions--for almost any cognitive task that is more difficult than an easier task." She therefore believes that fMRI lie detection would be vulnerable to countermeasures--performing arithmetic in your head, reciting poetry--that involve concerted cognitive effort. Moreover, the regions that allegedly make up the brain's "lying module" aren't that small...Saying 'You have activation in the anterior cingulate' is like saying 'You have activation in Massachusetts.' "

Kanwisher's complaint suggests that fMRI technology, when used cavalierly, harks back to two pseudosciences of the eighteenth and nineteenth centuries: physiognomy and phrenology. Physiognomy held that a person's character was manifest in his facial features; phrenology held that truth lay in the bumps on one's skull. In 1807, Hegel published a critique of physiognomy and phrenology in "The Phenomenology of Spirit." In that work, as the philosopher Alasdair MacIntyre writes, Hegel observes that "the rules that we use in everyday life in interpreting facial expression are highly fallible." (A friend who frowns throughout your piano recital might explain that he was actually fuming over an argument with his wife.) Much of what Hegel had to say about physiognomy applies to modern attempts at mind reading.

Elizabeth Phelps, a prominent cognitive neuroscientist at N.Y.U., who studies emotion and the brain, questions another basic assumption behind all lie-detection schemes--that telling a falsehood creates conflict within the liar. With the polygraph, the assumption is that the conflict is emotional: the liar feels guilty or anxious, and these feelings produce a measurable physiological response. With brain imaging, the assumption is that the conflict is cognitive:the liar has to work a little harder to make up a story, or even to stop himself from telling the truth. Neither is necessarily right. "Sociopaths don't feel the same conflict when they lie," Phelps says. "The regions of the brain that might be involved if you have to inhibit a response may not be the same when you're a sociopath, or autistic, or maybe just strange. Whether it's an emotional or a cognitive conflict you're supposed to be exhibiting, there's no reason to assume that your response wouldn't vary depending on what your personal tendencies are--on who you are."

Tuesday, July 10, 2007

When watching a tactile stroke is the same as receiving one.

An interesting report from Banissy and Ward (PDF here)... People who have 'mirror-touch' synesthesia, when watching another person being touched, have the same experience as being touched themselves...an extreme form of empathy! They developed a protocol to provide evidence for the authenticity of this form of synesthesia, in which participants have difficulty in discriminating between actual and synesthetic touch. Their abstract:

Watching another person being touched activates a similar neural circuit to actual touch and, for some people with 'mirror-touch' synesthesia, can produce a felt tactile sensation on their own body. In this study, we provide evidence for the existence of this type of synesthesia and show that it correlates with heightened empathic ability. This is consistent with the notion that we empathize with others through a process of simulation.

Making up our Minds...

Rebecca Saxe's review of "Making Up the Mind" by Chris Frith (Blackwell, 2007, 232 pp, paperback, $24.99) is a very nice summary of why we need an empirical science of the mind that does not rely on introspection, noting that experiences of how minds work, both our own and other people's, are just fantasies whose predictions often coincide with reality. Frith's book argues that there is no qualitative difference between perceiving the outside world and our own actions in it, compared with trying to infer the thoughts, feelings and goals inside other people's heads. Here is Saxe's review:

Perceiving the outside world and one's own actions in it might seem easy, at least when compared with trying to infer the thoughts, feelings and goals inside other people's heads. These intuitions are wrong, however, and debunking them is the main task of Chris Frith's new book, Making Up the Mind. The apparently effortless perceptions of the world and the self mask sophisticated computation and 'unconscious inferences'. On the other hand, he claims, these same kinds of inferences support access to other people's feelings and intentions. There is no qualitative difference between perceiving minds and perceiving anything else.

If perceiving the world is a hard problem, studying these perceptions is possibly a harder one. By their nature, 'unconscious inferences' are not accessible to introspection. Indeed, the major trick of the scientific psychologist's trade is to devise alternative nonintrospective methods for studying the mind. The need for such methods arises not just because conscious experiences are 'soft', imprecise or hard to verify, the reasons that Frith entertains in his prologue. More importantly, as he shows in the rest of the book, the contents of introspection are simply unreliable as guides to the real structure of the mind.

Frith is especially enthusiastic about one such method: studying the brain. Brain function provides a window onto the intermediate stages of mental computations, between the inputs at the senses and the outputs in behavior and conscious experience. These days, this approach is called 'cognitive neuroscience' and its popularity is booming with the increasing availability of noninvasive brain scanners.

Making Up the Mind is an accessible and enthusiastic introduction to the field, and a great way to whet the appetites of smart beginners. Particularly nice is Frith's clear affection for doing science. During one experiment, he remembers, "we all had a very exciting Saturday in the imaging laboratory, which is not reflected at all in the paper we wrote about it afterwards." At another point, he expands on a reference to "my lab" with this footnote, "In the 1960s, this was a small bathroom that had been converted into a 'laboratory' by putting a sheet of hardboard over the bathtub."

Part 1 of the book covers the most charismatic discoveries of cognitive and neuropsychology, the gaps between the real world and the world constructed by the mind: phantom limbs, blindsight, anosognosia, change blindness, color constancy (including a fantastic demo in the color plates), priming, motor adaptation, illusions of causal control, synesthesia, implicit memory, dreams and hallucinations. (Surprisingly, he doesn't mention confabulation or false memories, two other famous illustrations of his thesis that our brains 'make up' our world.) The message is that nothing that appears simple or direct in our perceptions of the world, and of ourselves, can be taken for granted.

So how does the brain construct the consciously experienced world? No one knows. Instead of giving an answer, Part 2 introduces some basic concepts: neurons and synapses, associative and operant conditioning, Bayesian inference, and forward and inverse models. The result is a useful informal survey of the foundations of current research.

Finally, in Part 3, Frith turns back to problems of perception, now focusing on the question of social perception: how we can ever 'know' about someone else's thoughts, feelings or goals? The situation, Frith claims, is not as bad as it looks. Other people's actions are represented in the same way we represent our own actions, using a forward model to predict their causal effects. Frith illustrates this idea with an illusion. When a sound acts as a signal to start an action, the cause (the sound) and the effect (the hand motion) are perceived to be closer together in time than they really are, both for one's own and other people's actions, but not for an externally caused event. Another great example that Frith does not mention, which was reported by Sebanz and colleagues, is that the (task-irrelevant) direction that an arrow is pointing interferes with participants' ability to respond on the basis of color, if and only if the arrow points to another possible action, either for the participant or for another person. That is, a representation of another person's possible (but unseen) actions can compete with the participant's own action plans.

In all, Making Up the Mind is an accessible, fun and up-to-date introduction to the hot ideas and phenomena in and around cognitive neuroscience. Only the conclusion feels out of place. In it, Frith writes that we all do successfully 'read minds', achieving direct access to other people's thoughts and goals. How we take this conclusion depends on what Frith means by success. It is true that inferences about other minds are not qualitatively harder than other inferences, but neither are they (as Frith sometimes implies) any easier or more accurate. Inferences about other minds have the same structure as self-perception, going beyond the data given using a sophisticated combination of prior knowledge and current data, and then masked by an illusion of effortlessness. As a result, inferences about others are just as prone to leaps, gaps and confabulations. The conclusion ought to leave us where the book began in the prologue. Psychologists who want to study the mind scientifically do not rely on social perceptions of the participants any more than they rely on introspection, precisely because social mind-reading fails. Our experiences of how minds work, both our own and other people's, are just fantasies whose predictions often coincide with reality. That is why we still do need an empirical science of the mind.

Monday, July 09, 2007

Tone deafness is associated with deficits in spatial processing

Representations of pitch and space in the brain seem to interact. An article from Douglas & Bilkey in Nature Neuroscience (PDF here) now reports that people with amusia, a pitch processing deficit, do not show the interference between these concepts that is found in control subjects. The abstract:

Amusia (commonly referred to as tone-deafness) is a difficulty in discriminating pitch changes in melodies that affects around 4% of the human population. Amusia cannot be explained as a simple sensory impairment. Here we show that amusia is strongly related to a deficit in spatial processing in adults. Compared to two matched control groups (musicians and non-musicians), participants in the amusic group were significantly impaired on a visually presented mental rotation task. Amusic subjects were also less prone to interference in a spatial stimulus-response incompatibility task and performed significantly faster than controls in an interference task in which they were required to make simple pitch discriminations while concurrently performing a mental rotation task. This indicates that the processing of pitch in music normally depends on the cognitive mechanisms that are used to process spatial representations in other modalities.
Here is a graphic from the review of this work by Janata in the same issue of Nature Neuroscience.

Figure... The link between musical and spatial processing was investigated via a set of tasks. (a) In a stimulus-response compatibility task, subjects press either the closer or farther of two buttons on a computer keyboard to indicate whether the second of two pitches is higher or lower than the first. The response that the second pitch was higher was made more quickly, on average, when the answer "higher pitch" was mapped to the 'higher' (farther) of the two response buttons, than when the response "lower pitch" was mapped to the higher button. (b) In the contour violation task from the Montreal Battery for the Evaluation of Amusia, subjects have to detect whether a single note in the repetition of a melody changed direction. Amusic individuals have extraordinary difficulty with this task. (c) In the Shepard and Metzler mental rotation task, subjects must determine whether two geometric figures are the same or different. (d) In the animal matching task, a large set of 15 animal pictures is shown to the subject along with a set of three probe pictures. Subjects must determine whether all three pictures from the small set are in the large set.

Some music to start the week...

Valse Romantique by Debussy, on my Steinway B at Twin Valley...

Ambiguity and anxiety: overreaction and a serotonin receptor

Nader and Alleine describe work of Tsetsenis et al.

When the threat of terrorist attack is elevated, the United States Department of Homeland Security changes its prediction of danger from yellow to orange to red. Most of us can manage our levels of vigilance and of anxiety appropriately in response to these cues. However, imagine how debilitating it would be if you were unable to manage your anxiety and reduce your fear of attack when the threat level was reduced. In fact, many people with anxiety disorders suffer from precisely this kind of condition. The paper by Tsetsenis et al. finds that mice lacking the serotonin 1a receptor overreact to ambiguous predictors of aversive events in this same way, providing insight into factors that could predispose individuals to such disorders and into the neural locus of the effect.

Understanding the neural bases of contingency is not simply an academic question, but very much a mental health one. Unpredictable aversive events can be much more stressful than the same events when they are anticipated. In addition, psychopathologies can influence the perception of contingency. For example, depressed people have a different sense than nondepressed people of how their responses affect the environment, and exposure to unpredictable or uncontrollable aversive events is suggested to directly influence the development of depression.

The new study by Tsetsenis et al. makes a significant contribution to our understanding of the neural mechanisms mediating contingency learning. The authors studied mice in which the serotonin 1a receptor (Ht1a) gene was knocked out or inactivated during development. This receptor causes membrane hyperpolarization of nonserotonergic neurons and acts as an autoreceptor on serotonergic neurons in the raphe. Ht1a dysfunction is linked to anxiety disorders and depression, and mice lacking Ht1a receptors show increased avoidance behavior. This phenotype is attributable to the absence of the Ht1a in the forebrain during development; eliminating these receptors during adulthood does not cause the mice to show the anxious phenotype. Although fear of an aversive context is comparable in knockout and wild-type mice, the knockout mice over-generalize their fear of the 'aversive' context to a similar context containing novel elements, a situation in which wild-type mice are able to decrease their fear levels11. This finding suggested that these mutant mice focus unduly on cues that have been paired with shock rather than on cues that have not.

Figure: Humans and other animals can accurately estimate the probability of danger from their experience of specific environments or cues and use this information to respond appropriately. A normal mouse (top) accurately estimates the threat from an ambiguous cue, a sleeping cat, and a less ambiguous cue, an alert cat, and is appropriately cautious or alarmed, respectively. In contrast, anxious people and animals, such as the Htr1a knockout mouse assessed by Tsetsenis et al. (bottom), often overestimate the danger represented by ambiguous cues and over-respond, given the level of threat. This is likely to interfere with the need to respond to other important events in the environment (such as cheese).

Here is the abstract from Tsetsenis et al.
Serotonin receptor 1A knockout (Htr1aKO) mice show increased anxiety-related behavior in tests measuring innate avoidance. Here we demonstrate that Htr1aKO mice show enhanced fear conditioning to ambiguous conditioned stimuli, a hallmark of human anxiety. To examine the involvement of specific forebrain circuits in this phenotype, we developed a pharmacogenetic technique for the rapid tissue- and cell type–specific silencing of neural activity in vivo. Inhibition of neurons in the central nucleus of the amygdala suppressed conditioned responses to both ambiguous and nonambiguous cues. In contrast, inhibition of hippocampal dentate gyrus granule cells selectively suppressed conditioned responses to ambiguous cues and reversed the knockout phenotype. These data demonstrate that Htr1aKO mice have a bias in the processing of threatening cues that is moderated by hippocampal mossy-fiber circuits, and suggest that the hippocampus is important in the response to ambiguous aversive stimuli.

Friday, July 06, 2007

Threads of our lives in dreams...

Rebecca Cathcart writes an article on dreaming and "big dreams" (PDF here) that resonates with my own experience of having, particularly before waking, emotionally intense dreams whose story line seems to be an obvious attempt to integrate important personal issues. Some clips:

Big dreams are once again on the minds of psychologists as part of a larger trend toward studying dreams as meaningful representations of our concerns and emotions...The dreaming imagination does not just harvest images from remembered experience...It has a “poetic creativity” that connects the dots and “deforms the given,” turning scattered memories and emotions into vivid, experiential vignettes that can help us to reflect on our lives....Cultural narratives in regions like Vietnam and North and South America assign special importance to such dreams and consider them actual encounters with the spirits of lost loved ones...This notion is so widely shared by traditions all across the globe that some scholars have gone so far as to argue that religion itself actually originated in dream experience.
The article emphasizes the role of dreams in dealing with death and grief.
Grief itself is transformative. It is a process of disassembly. The bereaved must let go of the selves they were, as well as the loved ones they have lost. The dreams we have while grieving are an important part of that process...Our dreams have to do with how we internalize the people we love...You learn to look within for the loved one and the particular function that person played in your life, such as caretaking or guidance in the case of a parent. This becomes part of a function that you can provide for yourself.

Dreams that occur during rapid eye movement, or REM, cycles are the most memorable and emotionally powerful...The dreams have power because brain activity during REM is most similar to that of a waking state. The emotional responses to REM dream content, therefore, are most like the responses during waking cognition...Core body temperature rises gradually from its nadir in the middle of the night during slow-wave sleep, the least active brain state. As morning nears, subcortical brain activity tied to the circadian cycle increases. When these cycles coincide in the last and longest REM phase... the mind produces its most dramatic dreams...the four or five phases of REM in a normal night’s sleep might include similar dream content. Just as the image of a lost loved one stimulates parts of the brain associated with loss, the content of dreams early in the sleep cycle could set the tone for that night’s dream experiences. Our memories upon waking, therefore, may be our recollection of a night’s cumulative dream content.

Thursday, July 05, 2007

Where the brain understands animate agents..

Wheatley et al offer an interesting study in a recent issue of Psychological Science (vol 18, pg 469, 2007, PDF here). Here is the abstract and two figures:

How people understand the actions of animate agents has been vigorously debated. This debate has centered on two hypotheses focused on anatomically distinct neural substrates: The mirror-system hypothesis proposes that the understanding of others is achieved via action simulation, and the social-network hypothesis proposes that such understanding is achieved via the integration of critical biological properties (e.g., faces, affect). In this study, we assessed the areas of the brain that were engaged when people interpreted and imagined moving shapes as animate or inanimate. Although observing and imagining the moving shapes engaged the mirror system, only activation of the social network was modulated by animacy.

Lateral and medial views of the social network (top, highlighted in yellow) and mirror system (bottom, highlighted in blue). The social network includes areas associated with biological motion (superior temporal sulcus, labeled "1"), biological form (lateral fusiform gyrus, labeled "6"), mentalizing (medial prefrontal cortex and posterior cingulate, labeled "3" and "4," respectively), and affective processing (insula and amygdala, labeled "2" and "5," respectively). The mirror system consists of the inferior parietal cortex (labeled "7") and the ventral-premotor/inferior-frontal cortex (labeled "8").


Experimental results. The brain slices in (a) depict areas of the social network that were more active when moving shapes were inferred (red) or imagined (orange) as animate than when they were inferred or imagined as inanimate. Yellow areas were more active for both animate inference and imagery ("conjunction"). The graph in (b) displays the average hemodynamic responses within the conjunction areas as a function of animacy (animate, inanimate) and condition (motion, imagery). (Results are not shown for the posterior insula, although this was also a conjunction area.) The illustration in (c) shows areas of the mirror system that were more active when subjects watched and made inferences about the moving shapes (purple) and when they imagined (dark blue) the moving shapes relative to when they viewed the backgrounds alone; light-blue areas were more active during both the motion and imagery conditions ("conjunction") than in the background condition. The graph in (d) shows the average hemodynamic responses of the conjunction mirror areas as a function of animacy and condition. For purposes of illustration, all group data are presented on the N27 (AFNI software) brain. Error bars represent standard errors. STS = superior temporal sulcus; PFC = prefrontal cortex.

Yawn to cool your brain?

A curious and slightly flakey bit: Eric Nagourney in Tuesday's Science section of the NY Times describes work by Gallup et al (PDF here) published in the Journal Evolutionary Psychology. It seems to me they might have actually measured brain temperature instead of just speculating about it. Nagourney notes the proposal by Gallup et al. that:

yawning... is a way for the body to cool the brain...volunteers yawned more often in situations in which their brains were likely to be warmer...To prove their theory that yawning regulates brain temperature when other systems in the body are not doing enough, the researchers took advantage of the well-established tendency of people to yawn when those around them do — the so-called contagious yawn...The volunteers were asked to step into a room by themselves and watch a video showing people behaving neutrally, laughing or yawning. Observers watching through a one-way mirror counted how many times the volunteers yawned...Some volunteers were asked to breathe only through their noses as they watched. Later, volunteers were asked to press warm or cold packs on their foreheads...“The two conditions thought to promote brain cooling (nasal breathing and forehead cooling) practically eliminated contagious yawning,” the researchers wrote.

The study may also help explain why yawning spreads from person to person...A cooler brain, Dr. Gallup said, is a clearer brain...So yawning actually appears to be a way to stay more alert. And contagious yawning, he said, may have evolved to help groups remain vigilant against danger.

Wednesday, July 04, 2007

Is Darwin due for an upgrade?

I would recommend you have a look at this article by Douglas Erwin (PDF here) on the prospects of a paradigm shift in evolutionary biology. Here are some clips:

...constructed from the 1930s to 1950s by early geneticists, paleontologists and others..the modern synthesis...holds that mutations to DNA create new variants of existing genes within a species. Natural selection, driven by competition for resources, allows the best-adapted individuals to produce the most surviving offspring. So adaptive variants of genes become more common...Computer simulations have shown how selection can produce a complex eye from a simple eyespot in just a few hundred thousand years.

In the past few years every element of this paradigm has been attacked. Concerns about the sources of evolutionary innovation and discoveries about how DNA evolves have led some to propose that mutations, not selection, drive much of evolution, or at least the main episodes of innovation, like the origin of major animal groups, including vertebrates.

Comparative studies of development have illuminated how genes operate, and evolve, and this places less emphasis on the gradual accumulation of small genetic changes emphasized by the modern synthesis. Work in ecology has emphasized the role organisms play in building their own environments, and studies of the fossil record raise questions about the role of competition. The last major challenge has argued for a hierarchical view of evolution, with selection occurring at many levels, including between species.

The Achilles’ heel of the modern synthesis.. is that it deals primarily with the transmission of genes from one generation to the next, but not how genes produce bodies. The recent discoveries in the new field of evolutionary developmental biology, or evo-devo, that the gene Pax-6 controls the formation of eyes in mice and humans, Nkx2.5 heart formation, and a suite of other genes the formation of the nervous system, has provided a means to investigate the genetic and developmental mechanisms influencing how the form of organisms has evolved, not just their genes.

Core gene networks appeared long ago that locked development onto a certain path (an example being a kernel of five key genes regulating development of the gut that appeared 500 million years ago). These events, small and large, limit the range of possibilities on which natural selection can act...just as the erosive power of a river changes the future options for the course of the river, so evolution itself changes future evolutionary possibilities.

The first cyanobacteria turned carbon dioxide into oxygen and set off a revolution that completely changed the chemistry of the oceans and atmosphere. Most species modify their environment and this often changes how selection affects them: they construct, at least in part, their own environment. As evolutionary biologists we have little understanding of what these processes mean for evolution.

Does all this add up to a new modern synthesis? There is certainly no consensus among evolutionary biologists, but development, ecology, genetics and paleontology all provide new perspectives on how evolution operates, and how we should study it. None of these concerns provide a scintilla of hope for creationists, as scientific investigations are already providing new insights into these issues. The foundations for a paradigm shift may be in place, but it may be some time before we see whether a truly novel perspective develops or these tensions are accommodated within an expanded modern synthesis.