....from his Sonata No. 10. I thought I might slip in another of my brief recordings, a bit of relief from the heavy neuroscience...
Friday, June 29, 2007
....from his Sonata No. 10. I thought I might slip in another of my brief recordings, a bit of relief from the heavy neuroscience...
There have been several reports that subliminal stimuli (such as flashing a picture of an angry face for 33 msec) can activate the amygdala even though the subject is unaware of the stimulus. Pessoa presented work at the recent ASSC meeting using more rigorous criteria for behavioral performance that suggests, to the contrary, that visibility or attention is required for the expression of the effect of valence on early visual processing (even as early as the 'automatic' parallel processing in V1.) A PDF of a recent Pessoa et al. article is here, and PDF of commentary on this work by Duncan and Barrett here). This work:
...shows that amygdala responses depend on visual awareness. Under conditions in which subjects were not aware of fearful faces flashed for 33 ms, no differential activation was observed in the amygdala. On the other hand, differential activation was observed for 67 ms fearful targets that the subjects could reliably detect. When trials were divided into hits, misses, correct rejects, and false alarms, we show that target visibility is an important factor in determining amygdala responses to fearful faces. Taken together, our results further challenge the view that amygdala responses occur automatically.Duncan and Barrett, in their commentary, suggest
...that the amygdala is acting to increase neural activity in the fusiform gyrus, thereby increasing the likelihood that visual representations that have affective value reach awareness. The psychological consequence is that a person’s momentary affective state might help to select the contents of conscious experience.
Visual awareness is associated with amygdala activation. In the Pessoa et al. study, participants viewed backwardly masked images of faces that depicted fear, presented for either 33 ms or 67 ms. All participants showed greater amygdala activation when viewing fearful faces that were presented for 67 ms, compared with faces that depicted neutral expressions. (a) Pessoa et al. found an increase in amygdala activation (as well as fusiform gyrus activation, which is not shown in the figure) only among those participants who showed objective awareness of 33 ms presentations of faces that depicted fear. (b) Participants who did not show objective awareness did not have significant increases in amygdala activation. Given the excitatory projections from the amygdala to the ventral visual stream, this finding suggests that the amygdala enhances visual awareness for objectives with affective value.
Thursday, June 28, 2007
Rafeal Malach gave an interesting talk at the recent ASSC meeting (PDF of article here) on work from his group that he thinks:
challenges the conventional models of human perception, which assume that sensory experience involves a critical interplay between activity in sensory cortex representing the stimulus and pre-frontal cortex which serves as an “observer” system- receiving and interpreting the patterns of activity originating in posterior, sensory cortex.In an fMRI study in which individuals were exposed to a highly engaging popular movie they find:
a surprisingly robust and wide-spread activation of most of the posterior part of the brain- which was remarkably “synchronized” across individuals watching the same movie. These results attest to the massive engagement of sensory cortex by naturalistic sensory stimuli. However, in contrast to this wide-spread activation in sensory cortex- we have found a remarkably little activation in frontal areas of the brain (Fig. 1).
Fig. 1 Brain activation during repeated movie presentation. Yellow regions show highly activated areas in posterior, sensory cortex. Note lack of activation in frontal areas and in the intriguing “intrinsic” islands in posterior cortex (arrows).
To examine this issue, and also to start mapping in more detail the functional organization of the various networks of pre-frontal cortex:
we have conducted a series of experiments in which we mapped brain activity during tasks that were explicitly targeted at eliciting “self-related” brain activity- such as introspection to visual and auditory modalities, or self-judgment evaluations. Although these were high level cognitive tasks of extreme complexity- our results show a remarkably consistent pattern of activity focused primarily on pre-frontal cortex (see yellow patches in figure 2)...The critical question was now- how do these areas behave when the task shifts to a purely perceptual one? The results were clear cut- the activity shifted now to a different set of areas- located more posteriorly in sensorymotorThe results are:
cortex (green patches in fig. 2).
Fig. 2 Comparing brain activity during reflective self-related tasks and during intense perception. Prefrontal areas (yellow patches) showed significant activation during self-related introspection and self judgment tasks. However a completely different and highly segregated network of more posterior areas were active during engaging perceptual tasks (green patches). No overlap was found between the two networks, and the prefrontal cortex was actually inhibited during intense perception. The results clearly rule-out the need for an “observer” function in self-related
cortex during perception.
... actually compatible with the strong intuitive sense we have of 'losing our selves' in a highly engaging sensory-motor act (such as watching a movie). They are intriguingly reminiscent of recurrent eastern philosophical themes which emphasize the ‘silencing' of the self during intense engagement with the outside world.
Wednesday, June 27, 2007
My april 26 post dealt with a New Yorker article describing the work of Dan Everett on the language of an Amazon people which he interprets as showing humans can invent language without recursion. At edge.org there is now an interesting further conversation between Everett, Steven Pinker, and Robert Van Valin.
Tuesday, June 26, 2007
David Freedberg (Art History, Columbia Univ.) and Vittorio Gallese (Neuroscience, Parma) offer an interesting perspective on possible relationships between mirror neuron systems and artistic experience. Here is their abstract (and PDF of article is here.), followed by some of their illustrations.
The implications of the discovery of mirroring mechanisms and embodied simulation for empathetic responses to images in general, and to works of visual art in particular, have not yet been assessed. Here, we address this issue and we challenge the primacy of cognition in responses to art. We propose that a crucial element of esthetic response consists of the activation of embodied mechanisms encompassing the simulation of actions, emotions and corporeal sensation, and that these mechanisms are universal. This basic level of reaction to images is essential to understanding the effectiveness both of everyday images and of works of art. Historical, cultural and other contextual factors do not preclude the importance of considering the neural processes that arise in the empathetic understanding of visual artworks.
Figure 1. Embodied simulation in esthetic experience: actions. The sense of exertion, which Michelangelo intended his figures to show as they struggle to escape from the block of stone, is effectively conveyed to the spectator. Michelangelo, Slave called Atlas, Florence, Academia (ca. 1520–1523), marble © Scala/Art Resource, NY.
Figure 2. Embodied simulation in esthetic experience: empathy for pain. The viewing of images of punctured or damaged body parts activates part of the same network of brain centers that are normally activated by our own sensation of pain, accounting for the feeling of physical sensation and corresponding shock upon observation of pressure or damage to the skin and limbs of others. Goya, Que hay que hacer mas? (What more is there to do?), plate 33 from Los Desastres de la Guerra (Disasters of War), etching, Biblioteque Nationale, Paris, France © Bridgeman-Giraudon/Art Resource, NY.
Figure 3. Embodied simulation in esthetic experience: implied gestures of the artist. The gestures that are only implicit in the marks on these works of art are corporeally felt by their spectators. (a) Jackson Pollock, Number 14: Gray (1948), enamel over gesso on paper, Yale University Gallery, The Katharine Ordway Collection © 2004 The Pollock-Krasner Foundation/Artists Rights Society (ARS), New York. (b) Lucio Fontana, Concetto Spaziale ‘Atteza’ (‘Waiting’) (1960), canvas, Tate Gallery, London © Tate Gallery, London/Art Resource, NY/ Fondazione Lucio Fontana, Milano.
Figure 4. The mirror neuron system in monkeys and humans. (a) Activation of the area F5 mirror neuron during motor-act observation. (b) Activation of the area F5 mirror neuron during action execution. For both conditions, six consecutive rasters (spike recordings) during six consecutive trials are shown. The arrows indicate the onset of observed and executed grasping. (a) and (b) modified, with permission, from Ref. . (c) Somatotopy of premotor and parietal cortices as revealed by fMRI during action observation. Activation foci are projected on the lateral surface of a standard brain (MNI). Red, activation during the observation of mouth grasping; green, activation during the observation of hand grasping; blue, activation during the observation of foot kicking. Overlap of colors indicates activation foci present during observation of actions made by different effectors.
Monday, June 25, 2007
This is the last day of the annual meeting of the Association for the Scientific Study of Consciousness. I'm going to wait and work up a few posts on some of what I think is the most interesting material over the next period of time. Las Vegas is beyond belief.... like apocalypse now.... it will take weeks for the sensory overload to fade away. Here is the Eiffel Tower in Paris, Las Vegas, and the view of the Bellagio fountains from my lunch in its restaurant (the only peaceful and quiet place in the city I found) ....
I subscribe to a service offered at feedburner.com that lets you see details of the traffic on your blog. I am passing on the titles of the five postings that it indicates have been read the most.
Watching a computer "be nice" activates our brain's agency and goal detectors
A new desciprtion of our inner lives…
A neural network that shares a common genetic origin with human intelligence.
Social Networks - the twenty-first century science?
The pianist in the mirror - human mirror neuron systems for motor learning
Paz et al show how the hippocampal-medial prefrontal cortex interactions thought to support memory consolidation are enhanced by correlated activities in regions around the hippocampus. Their introduction gives a quick summary of known steps in memory consolidation which provides context for their experiment, here are some edited clips:
The hippocampus plays a time-limited role in the formation of declarative memories, with memories gradually becoming independent of the hippocampus over time. It is believed that these remote memories are gradually transferred from the hippocampus to the neocortex for long-term storage..investigations indicate that the medial prefrontal cortex (mPFC) is critical for the consolidation of hippocampal-dependent memories. In trace-conditioning tasks for instance, hippocampal lesions cause a severe deficit when made soon after training, but not after a month, whereas mPFC lesions produce the opposite pattern of impairments. ...The role of mPFC activity in memory formation remains unclear. One possibility is that mPFC affects the transfer of hippocampal activity toward the neocortex. Consistent with this possibility, the mPFC projects to the rhinal cortices, the main route for impulse traffic into and out of the hippocampus...the present study was undertaken to test the idea that the mPFC influences memory formation by modulating interactions between the neocortex and hippocampus at the level of the rhinal cortices. To this end, we examined the relative timing of unit activity in the mPFC, PR, and ER cortices during the acquisition of a trace-conditioning task.And, here is the abstract of the paper:
Much data suggests that hippocampal–medial prefrontal cortex (mPFC) interactions support memory consolidation. This process is thought to involve the gradual transfer of transient hippocampal-dependent memories to distributed neocortical sites for long-term storage. However, hippocampal projections to the neocortex involve a multisynaptic pathway that sequentially progresses through the entorhinal and perirhinal regions before reaching the neocortex. Similarly, the mPFC influences the hippocampus via the rhinal cortices, suggesting that the rhinal cortices occupy a strategic position in this network. The present study thus tested the idea that the mPFC supports memory by facilitating the transfer of hippocampal activity to the neocortex via an enhancement of entorhinal to perirhinal communication. To this end, we simultaneously recorded mPFC, perirhinal, and entorhinal neurons during the acquisition of a trace-conditioning task in which a visual conditioned stimulus (CS) was followed by a delay period after which a liquid reward was administered. At learning onset, correlated perirhinal-entorhinal firing increased in relation to mPFC activity, but with no preferential directionality, and only after reward delivery. However, as learning progressed across days, mPFC activity gradually enhanced rhinal correlations in relation to the CS as well, and did so in a specific direction: from entorhinal to perirhinal neurons. This suggests that, at late stages of learning, mPFC activity facilitates entorhinal to perirhinal communication. Because this connection is a necessary step for the transfer of hippocampal activity to the neocortex, our results suggest that the mPFC is involved in the slow iterative process supporting the integration of hippocampal-dependent memories into neocortical networks.
Friday, June 22, 2007
Here is the abstract from Taziaux et al. Might this tempt pharmaceutical companies to go for a human male equivalent?
Estrogens are classically viewed as hormones that bind to intracellular receptors, which then act as transcription factors to modulate gene expression; however, they also affect many aspects of neuronal functioning by rapid nongenomic actions. Brain estrogen production can be regulated within minutes by changes in aromatase (estrogen synthase) activity as a result of calcium-dependent phosphorylations of the enzyme. To determine the effects of rapid changes in estrogen availability on male copulatory behavior, we mimicked in male mice the rapid upregulation and downregulation of brain estrogen concentration that should occur after inactivation or activation of aromatase activity. A single injection of different aromatase inhibitors [Vorozole, 1,4,6-androstatrien-3,17-dione (ATD), or its metabolite 17-OH-ATD (1,4,6-androstatrien-17ß-ol-3-one)] almost completely suppressed male sexual behavior (mounts and intromissions) expressed 10–20 min later by C57BL/6J mice but did not affect behavior in aromatase knock-out (ArKO) mice, activated by daily injections of estradiol benzoate, thereby confirming the specificity of the behavioral inhibition observed in wild-type mice. The rapid ATD-induced inhibition was reversed by the simultaneous injection of a large dose of estradiol. A single injection of estradiol to ArKO mice also activated male sexual behavior within 15 min. Thus, rapid increases or decreases in brain estrogen concentrations are followed within minutes by corresponding changes in male sexual behavior. Sexual behavior can thus be used to monitor changes in local estrogen concentrations and analyze the mechanisms mediating the rapid decline in estrogen signaling that takes place after inhibition of estrogen synthesis.
Robert K. Night writes a perspective in Science (PDF here) on how neural networks support goal-directed behavior:
Systems neuroscience aims to understand how billions of neurons in the mammalian brain support goal-directed behavior, such as decision making. Deciphering how individual neurons respond to sensory inputs or motor decisions has focused on delineating the neural basis of these processes in discrete regions of the brain's cortex, and has provided key insights into the physiological basis of behavior. However, evidence from neuropsychological, electrophysiological, and neuroimaging studies in humans has revealed that interactions between widespread neural regions in the brain underlie fluid, organized behavior.He then summarizes work reported in three papers to:
...unravel the details of these interactions by assessing the simultaneous activity of neurons in multiple sites of the mammalian brain. The studies show that network interactions among anatomically discrete brain regions underlie cognitive processing and dispel any phrenological notion that a given innate mental faculty is based solely in just one part of the brain.
...Taken together, the three papers indicate that top-down signals between brain regions regulate the flow of information and that distributed neural networks that use oscillatory dynamics support a broad spectrum of neural processing and behavior. The results in cats and monkeys also nicely parallel findings in humans...this particular coupling mechanism is used to delineate task-specific network activity
Thursday, June 21, 2007
I'm taking off now for the annual meeting of the Association for the Scientific Study of Consciousness meeting in Las Vegas, June 22-25, at the Imperial Palace Hotel on the Strip. The program looks fascinating, with many luminaries in the field of consciousness studies. A special feature is a show by famous magicians and illusionists illustrating the psychological and perceptual tricks they employ.
Perhaps I'll have time to give you some "dispaches from the front." Otherwise, I'll try to present some bon-bons from the meeting on this blog when I get back.
From the Assoc. for the Scientific Study of Consciousness eprint committee, the five most popular (i.e. most downloaded from the eprint archive) papers of May 2007:
1. Sagiv, N. and Ward, J. (2006) Crossmodal interactions: lessons
from synesthesia. Progress in Brain Research,155. (1428 downloads from
22 countries). http://eprints.assc.caltech.edu/224/.
2. Windt, J.M. and Metzinger, T. (2006) The philosophy of dreaming and
self-consciousness: What happens to the experiential subject during
the dream state? In: The new science of dreaming (1063 downloads from
22 countries). http://eprints.assc.caltech.edu/200/.
3. Block, N. (2007) Consciousness, Accessibility and the Mesh between
Psychology and Neuroscience. Behavioral and Brain Sciences,
forthcoming. (991 downloads from 18 countries).
4. Robbins, S. E (2006) Bergson and the holographic theory of mind.
Phenomenology and the Cognitive Sciences, 5. (984 downloads from 19
5. Koriat, A. (2006) Metacognition and Consciousness. In: Cambridge
handbook of consciousness. Cambridge University Press, New York, USA.
(941 downloads from 23 countries).
Further information: http://eprints. assc.caltech.edu
A recent study by Harbaught et al. finds that three very different things—monetary payoffs to oneself, observing a charity get money, and a warm-glow effect related to free choice—all activate similar neural substrates. Here is their abstract, PDF of article is here.
Civil societies function because people pay taxes and make charitable contributions to provide public goods. One possible motive for charitable contributions, called "pure altruism," is satisfied by increases in the public good no matter the source or intent. Another possible motive, "warm glow," is only fulfilled by an individual's own voluntary donations. Consistent with pure altruism, we find that even mandatory, tax-like transfers to a charity elicit neural activity in areas linked to reward processing. Moreover, neural responses to the charity's financial gains predict voluntary giving. However, consistent with warm glow, neural activity further increases when people make transfers voluntarily. Both pure altruism and warm-glow motives appear to determine the hedonic consequences of financial transfers to the public good.
Figure: Neural response in the ventral striatum to mandatory payoffs for the subject (yellow), the charity (blue), and both (green). (To test for the pure altruism and warm-glow motives, they used functional magnetic resonance imaging while subjects played a dictator game. Subjects received $100 and then made decisions about whether or not to give money to a local food bank. They also observed mandatory, tax-like transfers of their money to the food bank.)
They suggest that:
...This result supports arguments for a common "neural currency" of reward and shows that this model can be applied not just to choice over money, risk, and private consumption goods, but also to more abstract policy choices involving taxation and charitable giving. Our results are also important for understanding why people give money to charitable organizations. First, these transfers are associated with neural activation similar to that which comes from receiving money for oneself. The fact that mandatory transfers to a charity elicit activity in reward-related areas suggests that even mandatory taxation can produce satisfaction for taxpayers. A better understanding of the conditions under which taxation elicits "neural rewards" could prove useful for evaluating the desirability of different tax policies.
Wednesday, June 20, 2007
Dan Jones writes an interesting essay in a recent issue of Science (PDF here) on how work in evolutionary theory, moral philosophy, and neuroscience casts doubt on the idea that disgust embodies a deep-seated wisdom. Instead it provides an emerging portrait of an evolutionarily constrained emotion that is a poor guide to ethical action. Here are some edited clips from his article:
Although the experience of disgust feels primal, the emotion does not seem to be widespread in other animals. Many species exhibit distaste in response to the sensory properties of food — such as sourness and bitterness — and a monkey, cat or human infant might spit out something disagreeable. But only humans beyond infancy will reject food on the basis of where it might have been and what it might have touched.
A clue is the language of moral indignation itself...All cultures and languages that we have studied have at least one word that applies both to core disgust (cockroaches and faeces) and also to some kind of social offence, such as sleazy politicians or hypocrites...people labelled as disgusting in this way evoke fears of contamination just as rotting food does...disgust drives some moral judgements, but ... they are mainly those relating to behaviour that involves bodily fluids or contact — gay sex, for instance — rather than more abstract issues.
Clues suggest a physiological reality for moral disgust. Whereas anger pushes the heart rate up, being viscerally disgusted makes it drop. Experiments done by Haidt and Sherman showed
... people hooked up to a heart monitor video footage of morally negative but not viscerally disgusting behaviour, such as an American neo-Nazi meeting. The participants said that the video triggered disgust and anger, and on average their heart rates fell, not rose. What's more, those who reported increased clenching in their throat had a greater drop in heart rate, making the link with core disgust look stronger.
...this is the first physiological evidence that socio-moral disgust really is disgust and not just metaphor or anger.
Brain imaging studies might also point to an overlap between core and moral disgust... Moll...used magnetic resonance imaging (MRI) to monitor the flow of blood in the brains of 13 healthy adult volunteers as they mulled over situations evocative of core disgust and those that elicit self-reported moral disgust or indignation. He found that core and moral disgust recruit overlapping brain areas, particularly the lateral and medial orbitofrontal cortex, suggesting that the emotions are related. These regions of the brain are activated by unpleasant sensory stimuli, and they connect with other emotion-related areas, such as the amygdala.
Evolution suggests that the human moral faculty — the psychological systems that make judgements about right and wrong, what's permissible and what isn't — was cobbled together from pre-existing brain systems over millions of years of biological and cultural evolution. Along the way, it latched onto disgust as a useful tool...The experimental data point to the possibility that our disgust system might have been adapted by evolution to allow us to reject or disapprove of abstract concepts such as ideologies and political views that are deeply influenced by culture, as well social groups associated with 'disgusting' concepts...In making symbolic distinctions between us and them visceral, disgust could potentially foster greater cohesion within groups by bringing people together in defence against a common out-group...Disgust works for the group as it does for the individual — what is in the group is 'me' and what is not is 'not me'...Where core disgust is the guardian of the body, moral disgust acts as the guardian of social body — that's when disgust shows its ugliest side.
...disgust is an emotion we are stuck with. Heuser suggests that the challenge... is to make people more reflective about what they say and think. He cites the success that advocates of political correctness have had in lowering the prevalence of casually sexist and racist language. Moll suggests optimistically that cultivating cultural and personal values of tolerance and empathy could function as an antidote to the toxic effects of disgust...by thinking less with our guts, and more with our heads and hearts, we might be able push back the boundaries of our moral world.
As in this Figure, Beauty or beast: things that once disgusted can in new contexts be tolerated.
This neat test from the BBC, based on Paul Ekman's work.
Tuesday, June 19, 2007
From Tomasello's group, work with Malinda Carpenter and Ulf Liszkowski on "A New Look at Infant Pointing" (PDF here).
We propose a new theory of infant pointing involving multiple layers of intentionality and shared intentionality. In the context of this theory, we argue and present evidence for a rich interpretation of prelinguistic communication, that is, one which posits that when 12-month-old infants point for an adult they are in some sense trying to influence her intentional/mental states. Moreover, we also argue and present evidence for a deeply social view in which infant pointing is best understood - on many levels and in many ways - as depending on uniquely human skills and motivations for co-operation and shared intentionality (e.g., joint intentions and attention with others). We conclude with a defense of the claim that children's initial skills of linguistic communication emerge on the heels of their initial pointing gestures because these two forms of interpersonal communication share a common social-cognitive, social-motivational infrastructure.
Almost anything about music attracts my attention, and I thought this was a fascinating demonstration of standing waves and sound visualization.
Battelli et al provide a nice review (PDF here) in the May issue of Trends in Cognitive Sciences:
The order of events, whether two events are seen as simultaneous or successive, sets the stage for the moment-to-moment interpretation of the visual world. Evidence from patients who have lesions to the parietal lobes and transcranial magnetic stimulation studies in normal subjects suggest that the right inferior parietal lobe underlies this analysis of event timing. Judgment of temporal order, simultaneity and high-level motion are all compromised following right parietal lesions and degraded after transcranial magnetic stimulation over the right parietal but not elsewhere. The results suggest that the right parietal lobe serves as part of a when pathway for both visual fields. We propose that the disruption of this mechanism is the underlying cause of a wide range of seemingly unrelated tasks being impaired in right parietal patients.
Figure. The when pathway. The when pathway is represented in the brain. This pathway is lateralized in the right hemisphere. Information from the primary visual cortex (V1) travels along the dorsal pathway (spatial perception, determining where objects are) or the ventral pathway (object recognition, determining what objects are), according to the classical subdivision that has been proposed based on animal models. A third pathway coming from V1 is dedicated to using time information to identify objects (e.g. determining when objects appeared or disappeared). Here, the temporoparietal junction (TPJ; considered the most common substrate of neglect) is identified as a core anatomical locus, within the inferior parietal lobe (IPL); however, the when pathway is likely to include a bigger network of areas, including the right angular gyrus (Ang), the supramarginal gyrus (Smg) and the posterior superior temporal sulcus (included in the superior temporal gyrus, STG). All these areas are often involved in the cortical lesion of right parietal patients. The intraparietal sulcus (IPS) separates the IPL from the superior parietal lobe (not labeled). The middle temporal area MT+ is reported in yellow (also called the motion area, highly specialized in detecting and discriminating moving stimuli).
Monday, June 18, 2007
One effort to rescue free will from the implication's of Libet's famous experiment (showing brain activity underlying an action starts before we are of aware of intending that action) has been to say "OK, even if "it" has started the action before "we" intended it, we can still shut it off. We still have "free won't."
Aron et al have now shown that the ability to stop motor reponses may involve a "hyperdirect" pathway between the right inferior frontal cortex and the basal ganglia (PDF of article here). Here is their abstract, followed by a figure from the paper:
The ability to stop motor responses depends critically on the right inferior frontal cortex (IFC) and also engages a midbrain region consistent with the subthalamic nucleus (STN). Here we used diffusion-weighted imaging (DWI) tractography to show that the IFC and the STN region are connected via a white matter tract, which could underlie a "hyperdirect" pathway for basal ganglia control. Using a novel method of "triangulation" analysis of tractography data, we also found that both the IFC and the STN region are connected with the presupplementary motor area (preSMA). We hypothesized that the preSMA could play a conflict detection/resolution role within a network between the preSMA, the IFC, and the STN region. A second experiment tested this idea with functional magnetic resonance imaging (fMRI) using a conditional stop-signal paradigm, enabling examination of behavioral and neural signatures of conflict-induced slowing. The preSMA, IFC, and STN region were significantly activated the greater the conflict-induced slowing. Activation corresponded strongly with spatial foci predicted by the DWI tract analysis, as well as with foci activated by complete response inhibition. The results illustrate how tractography can reveal connections that are verifiable with fMRI. The results also demonstrate a three-way functional–anatomical network in the right hemisphere that could either brake or completely stop responses.
Figure. Diffusion-weighted tractography results. A, 3-D rendering of the tracts between the right IFC, the right preSMA, and the right STN region. B, Triangulation method for determining the third point in a network from the other two. Tracts originating in one brain area are overlaid on tracts originating from another. The overlap is superimposed on a gray matter mask in standard space. Tracts clearly overlap in the white matter space, but the overlap in gray matter is fairly unique: the preSMA only for tracts originating in the IFC and STN regions; the IFC and anterior prefrontal cortex (not shown) for tracts originating in the preSMA and the STN region and the thalamus only for tracts originating in the preSMA and the IFC.
This from Panskepp. You might check out his other work on affiliative behavior and play. This article has relevant references and links.
Thielscher and Pessoa (PDF here) have examined brain activation that reflects perceptual choices using fMRI during a two-choice perceptual discrimation task of fearful versus disgusted faces. From their abstract:
...Our analyses revealed that reporting a neutral face as "fearful" was associated with activation in a broad network of brain regions that process emotionally arousing stimuli, whereas reporting a neutral face as "disgusted" was associated with activation in a focused set of sites that included the putamen and anterior insula...fluctuations in fMRI amplitude for an individual participant could be used to reliably predict the perceptual choice of individual trials for that subject. In addition to the investigation of choice, we also isolated the neural correlates of decision making per se by using reaction time as an index of decision processes. Overall, our findings revealed that brain responses dynamically shifted according to perceptual choices. In addition, the neural correlates of decision making involved at least the anterior cingulate cortex, middle frontal gyrus, and inferior frontal gyrus/insula, consistent with recent proposals that decisions may emerge from distributed processes.
A review of this work by Tobler and Kalenscher (PDF here) provides a useful summary graphic:
Figure 1. Top, Model of decision process. Bottom, Selected decision-related activations. Regions in orange predict whether a fearful or a disgusted face has been presented. Regions in blue predict whether the participant will choose "fearful" or "disgusted," and regions in yellow correlate with decision as operationalized by trial-to-trial changes in reaction time.
Friday, June 15, 2007
I have now cruised through the 500+ posts of MindBlog since it started up in Feb. of 2006 and done a cursory job of adding keywords to each. Using the labels list to the left, you can pull up all the posts in the areas of greatest interest to me. While I was tempted to distinguish many more categories, I thought this would get unwieldy and run the list too far down the screen, so I've limited the labels or keywords to about 35 items. Here is a list of labels I was also tempted to
add as I went through the old posts:
BUT, entering any of these in the blog search box provided by Google in the left column also gets you there. The Google search function proves to be very powerful for more focused searches, as for specific brain structures (insula, amygdala, whatever....)., or experiments using MRI imaging, etc.
Ross, Choi and Purves (PDF here) offer a fascinating study how vocal tract anatomy and vocal language sounds might explain why humans, across cultures, have created music using pitch intervals that divide octaves into the 12 tones of the chromatic scale:
Throughout history and across cultures, humans have created music using pitch intervals that divide octaves into the 12 tones of the chromatic scale. Why these specific intervals in music are preferred, however, is not known. In the present study, we analyzed a database of individually spoken English vowel phones to examine the hypothesis that musical intervals arise from the relationships of the formants in speech spectra that determine the perceptions of distinct vowels. Expressed as ratios, the frequency relationships of the first two formants in vowel phones represent all 12 intervals of the chromatic scale. Were the formants to fall outside the ranges found in the human voice, their relationships would generate either a less complete or a more dilute representation of these specific intervals. These results imply that human preference for the intervals of the chromatic scale arises from experience with the way speech formants modulate laryngeal harmonics to create different phonemes.
The periodicity in speech sound stimuli is generated primarily by the repeating peaks of energy in the vocal air stream produced by oscillations of the vocal folds in the larynx. The intensity carried by the harmonic series produced in this way is altered, however, by the resonance frequencies of the rest of the vocal tract, which change dynamically in response to neurally controlled movements of the soft palate, tongue, lips and other articulators (see figure). These variable vocal tract resonances, called formants, modulate the harmonic series generated by the laryngeal oscillations by suppressing some harmonics more than others. When coupled with unvoiced speech sounds (consonants), this modulation by the formants creates the different voiced speech sounds that give rise to the semantic content in all human languages. With respect to vowel phones, only the first two formants have a major influence on the vowel perceived: artificially removing them from vowel phones makes vowel phonemes largely indistinguishable, whereas removing the higher formants has little effect on the perception of speech sounds. Indeed, the first and second formants of vowel sounds of all languages fall within well defined frequency ranges. The resonances of the first two formants are typically between approximately 200–1,000 Hz and approximately 800–3,000 Hz, respectively, their central values approximating the odd harmonics of the resonances of a tube approximately 17 cm in length open at one end, the usual physical model of the adult vocal tract in a relaxed state).
Figure - Ranges of the peak harmonic in the first two formants (F1 and F2) for eight American English vowels uttered as single words in an emotionally neutral manner. (A) Diagram of the human larynx and vocal tract; see Introduction for explanation. (B) Distribution of the peak harmonics selected as the index for the first and second formant for the five male participants. (C) Distribution for the five female participants. The somewhat smaller harmonic ranges for females are due to the higher average fundamental frequency of female speech. The mean fundamental frequency for male speakers was 109 Hz (SD = 10) and for female speakers 171 Hz (SD = 20).
Laptop just like the one I'm using right now...
Anyone who has ever thrown around a stack of liras or rupees knows that people are sometimes more extravagant with currencies that have high face values. A paper recently published in The Journal of Consumer Research explored that effect...In one study, students in Hong Kong, when asked to allocate spending from an imaginary paycheck of 9,000 Hong Kong dollars, devoted an average of 532.35 of those dollars to food spending...Two weeks later, the students were asked to imagine that they had moved to the fictional country of Tristania, where a Hong Kong dollar equaled 18 Tristanian dollars, and therefore their pay was 162,000 Tristanian dollars. The students splurged, spending 30 percent more on food in real terms...The opposite effect was seen among students sent to an alternate Tristania where their paychecks were worth only 500 Tristanian dollars...“You feel more rich if you have more units of currency,” said Dilip Soman, a professor of marketing at the University of Toronto, and one of the paper’s authors...Earlier studies have been taken to suggest the opposite — that consumers are wary of spending in “numerous” foreign currencies, because they are put off by the high numbers on price tags. But Mr. Soman said that those studies had not taken budgeting into account.
Thursday, June 14, 2007
Leuner et al offer a nice review PDF here) of work by Tashiro et al. showing that survival of the thousands of new nerve cells that are born in the dentate gyrus of the hippocampus each day is enhanced if mice are exposed to new experiences during a critical window of time. Here is Tashiro et al.'s abstract, followed by a summary diagram from the Leuner review.
Neural circuits in the dentate gyrus are continuously modified by adult neurogenesis, whose level is affected by the animal's experience. However, it is not known whether this experience-dependent anatomical modification alters the functional properties of the dentate gyrus. Here, using the expression of immediate early gene products, c-fos and Zif268, as indicators of recently activated neurons, we show that previous exposure to an enriched environment increases the total number of new neurons and the number of new neurons responding to reexposure to the same environment. The increase in the density of activated new neurons occurred specifically in response to exposure to the same environment but not to a different experience. Furthermore, we found that these experience-specific modifications are affected exclusively by previous exposure around the second week after neuronal birth but not later than 3 weeks. Thus, the animal's experience within a critical period during an immature stage of new neurons determines the survival and population response of the new neurons and may affect later neural representation of the experience in the dentate gyrus. This experience-specific functional modification through adult neurogenesis could be a mechanism by which new neurons exert a long-term influence on the function of the dentate gyrus related to learning and memory.
Here is a summary figure of the results (NeuN+ is a marker for nerve cells; BrdU is a marker for new neurons; Zif268 is a marker for increased neural activation.
Figure legend: Simplified schematic diagram of the results presented by Tashiro et al. (2007). Exposure to environmental enrichment during a critical period (1–3 weeks after BrdU administration; bottom) increased the survival of new neurons in the dentate gyrus (BrdU+/NeuN+). In contrast, new neuron survival was not enhanced in mice exposed to an enriched environment after the critical period (top). The authors also demonstrated that reexposure to the same experience of environmental enrichment at a later time enhanced neuronal activation (BrdU+/NeuN+/Zif268+; bottom). Increased neuronal activation did not occur when mice were only given the initial exposure or were reexposed to a different experience of water maze training.
El comportamiento homosexual en animales como el carnero, el búfalo y el bonobo...
Here is a more extended commentary on a paper I mentioned in my Jan. 30 post "The pianist in the mirror.." D'Ausilio (PDF here) discusses this work of Lahav et al. showing an auditory mirror area in the left inferior frontal gyrus for complex and newly acquired actions. In addition to rote auditory-motor mapping for learning and online execution control, this mirror mechanism might subserve other evolutionary critical functions like action recognition, and interindividual emotional resonance. This auditory mirror-like property seems indeed to be valid for a wide range of functions that in turn elicit very different behaviors.
Wednesday, June 13, 2007
I recommend reading Adami's review (PDF here) of Douglas Hofstadter's recent book on consciousness "I am a Strange Loop," Basic Books, New York, 2007. A few excerpts:
Hofstadter's explanation of human consciousness is disarmingly simple...the main idea is simply that our feeling of a conscious "I" is but an illusion created by our neuronal circuitry: an illusion that is only apparent at the level of symbols and thoughts, in much the same way as the concepts of pressure and temperature are only apparent at the level of 10^23 molecules but not the level of single molecules. In other words, Hofstadter denies consciousness an element of ontological reality, without denying that our thoughts and feelings, pains and longings have an "inner reality" when we have them.
Hofstadter's book and Koch's recent "The Quest for Consciousness" make for an interesting juxtaposition. Each addresses the same problem but entirely on different levels. Yet both authors reach some of the same conclusions, sometimes using precisely the same metaphor (as when they compare the activity of "making up one's mind" in terms of a voting process). In the end, both authors could have profited from peeking at each other's arsenal: Hofstadter would probably be delighted to see some of the putative neural underpinnings of consciousness, to peer underneath the strange loop as it were, at the inordinately complex firework and the neuroanatomy that supports it. For his part, Koch would no doubt appreciate the computational trick that Gödel incompleteness plays on us, as well as the developmental aspect of consciousness that Hofstadter advocates.
Geory Striedter writes a review of David Linden's new book "The Accidental Mind: How Brain Evolution Has Given Us Love, Memory, Dreams, and God" ..Harvard University Press: 2007. (PDF of the review is here) Some clips:
The human brain, and hence the human mind, is not an optimal, designed-from-scratch apparatus. Rather, it is an imperfect amalgam of shoddy components. That is the central thesis of David Linden's new book The Accidental Mind. Neurons are slow, leaky, and unreliable — hardly ideal computing elements. The whole brain, too, is not designed to the plan of some omnipotent engineer. Instead, evolution has endowed it with plenty of 'anachronistic junk'. Which is why, according to Linden, our minds often distort reality and can lead us to act foolishly. For example, when you reach out to touch something, your brain filters out what it expects. This selective neglect of expected input allows us to focus on unexpected stimuli, but it can be counterproductive. It may explain, for instance, why pushing and shoving confrontations tend to escalate. When someone pushes you, you feel it more than when you push the other with the same force, because the sensation caused by your own push is largely, though unconsciously, expected by your brain.
Linden tells his story well, in an engaging style, with plenty of erudition and a refreshing honesty about how much remains unknown. The book should easily hold the attention of readers with little background in biology and no prior knowledge of brains. It would make an excellent present for curious non-scientists and a good book for undergraduates who are just entering into the brain's magic menagerie. Even readers trained in neuroscience are likely to enjoy the many tidbits of rarely taught information — on love, sex, gender, sleep and dreams — that spice up Linden's main argument.
Tuesday, June 12, 2007
..whether unconscious information can influence the cognitive control system in the human prefrontal cortex. Volunteers had to prepare to perform either a phonological judgment (whether the word is bisyllabic) or a semantic judgment (whether the word refers to concrete objects) on an upcoming word, based on the instruction given at the beginning of each trial. However, in some trials they were visually primed to prepare for the alternative (i.e., "wrong") task, and this impaired their performance. This priming effect is taken to depend on unconscious processes because the effect was present even when the volunteers could only discriminate the identity of the primes at chance level. Furthermore, the effect was stronger when the visibility of the prime was near zero than when the visibility of the prime was significantly higher. When volunteers were unconsciously primed to perform the alternative task, there was also decreased neural activity in the brain areas relevant to the instructed task and increased neural activity in the brain areas relevant to the alternative task, which shows that the volunteers were actually engaged in the wrong task, instead of simply being distracted. Activity in the mid-dorsolateral prefrontal cortex was also found to be associated with this unconscious priming effect. These results suggest that the cognitive control system in the prefrontal cortex is not exclusively driven by conscious information, as has been believed previously.
Neural activity associated with priming. (Click to enlarge). Data were extracted from the brain areas that were previously found to be associated with the Phonological task (left ventral premotor area) and the Semantic task (left inferior frontal cortex and middle temporal gyrus). The location of these is schematically illustrated on the brain above. Here, task relevant means activity from the Semantic areas when the volunteers were instructed to perform the Semantic task, and activity from the Phonological areas when they were instructed to perform the Phonological task. Task irrelevant means the activity was extracted from the alternative areas, which was more important for the primed task than the instructed task. When the visibility of the primes was low (LoVis), which means the priming effect was strongest, activity in task-relevant areas was significantly reduced (p = 0.019), and activity in task-irrelevant areas was significantly increased (p = 0.045). This suggests that the volunteers were actually engaged in exercising the wrong neural circuits when they were primed to perform the wrong task. This effect is not present when the visibility of the primes was high (HiVis), suggesting that this effect could not be attributable to the degree of conscious perception of the prime. This is reflected by a three-way interaction between Task Relevance (i.e., activity in task relevant areas vs activity in task irrelevant areas), Congruency (Con; between prime and instruction), and Visibility (of the prime) (p = 0.040). InCon, Incongruency; n.s., not significant.
Mid-DLPFC and unconscious priming. (Click to enlarge) Lau et al. looked for activity in the brain that was associated with the unconscious priming effect in general, regardless of which task was explicitly cued, by testing for the interaction between Congruency (Con; between prime and instruction) and Visibility (of the prime). This test revealed activity in the mid-DLPFC (right; x = –38). This effect was specific to the Low-Visibility condition, in which volunteers did not consciously perceive the primes. InCon, Incongruency; n.s., not significant; HiVis, high visibility; LoVis, low visibility.
Need help opening that jar?
Monday, June 11, 2007
I always perk up when I see reports of new side effects of sildenafil (Viagra), because it is an inhibitor of one form of an enzyme, cyclic GMP phosphodiesterase, that my earlier research showed to be central to changing light into a nerve signal in the rod and cone cells of our retinas (check here if you are curious about this previous life..). One of the interesting side effects of viagra is on color vision. Here is another interesting bit from Agostino et al. in PNAS:
Mammalian circadian rhythms are generated by a master clock located in the suprachiasmatic nuclei and entrained by light-activated signaling pathways. In hamsters, the mechanism responsible for light-induced phase advances involves the activation of guanylyl cyclase, cGMP and its related kinase (PKG). It is not completely known whether interference with this pathway affects entrainment of the clock, including adaptation to changing light schedules. Here we report that cGMP-specific phosphodiesterase 5 is present in the hamster suprachiasmatic nuclei, and administration of the inhibitor sildenafil (3.5 mg/kg, i.p.) enhances circadian responses to light and decreases the amount of time necessary for reentrainment after phase advances of the light–dark cycle. These results suggest that sildenafil may be useful for treatment of circadian adaptation to environmental changes, including transmeridian eastbound flight schedules.
Friday, June 08, 2007
If you are seeing old posts in your feed, go directly to the blog. During this next period when I am adding labels (keywords) to old posts, the RSS feed may be presenting the old posts as new posts. I'll try to get around this by usually reposting the last five or so most recent posts when I have finished a session of labeling. Also, the previous posts shown in the adjacent right column are in the right sequence.
Synesthesia, in which letters or numbers elicit color perception, could be due to increased brain connectivity between relevant regions, or due to failure to inhibit feedback in cortical circuits. Diffusion tensor imaging now provides evidence for increased connectivity in word processing and binding regions of the brain. Hubbard comments (PDF here) on the article by Rouw and Scholte (PDE here):
If looking at this page of text causes you to see a cascade of colors, you have grapheme-color synesthesia, in which viewing letters and numbers in black and white elicits the experience of seeing colors... grapheme-color synesthesia occurs in as many as 2 out of every 100 people...To study this:
...the authors used diffusion tensor imaging (DTI), a neuroimaging technique that measures the diffusion of water molecules in the living human brain. Water molecules diffuse more easily parallel than perpendicular to the direction of white-matter fibers, because of the myelin sheaths and axonal membranes. By measuring relative differences in how easily water diffuses along different axes (termed fractional anisotropy), it is possible to infer the size, orientation and degree of myelination of white matter tracts in vivo... this technique demonstrated increased structural connectivity in synesthetes compared with controls in three brain regions: the right fusiform gyrus, which is near regions involved in word and color processing, and the left intraparietal sulcus (IPS) and frontal cortex, both of which are part of a network of regions involved in binding and consciousness
Figure - The outer cortical surface with relevant brain regions indicated.
The color-selective hV4 is indicated in red, and the visual word form area is indicated in green. Cross-activation between these regions, mediated by increased anatomical connectivity, correlates with the generation of the additional experiences of grapheme-color synesthesia, and the degree of connectivity determines their strength. The posterior IPS, thought to be involved in binding, is in blue. Additional anatomical connectivity in this region may be critical for synesthetic binding, which must operate on the colors generated by the cross-activation between grapheme regions and hV4. These regions have been projected to the left hemisphere for simplicity.
Here is Evolushark (spelling evolution) - to intimidate the conservation Christian mascot Ichthys.
Blocking out a distracting memory is something like ignoring an old (and perhaps distracting) acquaintance... it that much harder to reconnect the next time around...recent studies suggest that the brain plays favorites with memories in exactly this way, snubbing some to better capture others. A lightning memory... is not so much a matter of capacity as it is of ruthless pruningThe experiments:
...had 20 young men and women, mostly Stanford students, view in quick succession a list of 240 word pairs. These included 40 capitalized words, each paired with six related, lower-case words: For example, “ATTIC-dust,” “ATTIC-junk,” and so on....After studying the pairs, the participants were instructed to memorize three selected pairs from each of 20 capitalized words. In effect, this forced them to flag individual pairs, like ATTIC-dust, while trying to tune out very similar, distracting ones, like ATTIC-junk, for half of the total list of pairs they saw...They were told not to memorize any pairs from the other half of the list.....while participants were having their brains scanned by an M.R.I. machine, each person’s memory was tested several times, and scores ranged from about 30 percent accuracy to 80 percent. ...how well each person suppressed the distracting word pairs was also measured by comparing recall of those pairs with recall of the half of the list that was studied at first but later ignored.from Kulh et al.'s abstract:
Functional magnetic resonance imaging during selective retrieval showed that repeated retrieval of target memories was accompanied by dynamic reductions in the engagement of functionally coupled cognitive control mechanisms that detect (anterior cingulate cortex) and resolve (dorsolateral and ventrolateral prefrontal cortex) mnemonic competition. Strikingly, regression analyses revealed that this prefrontal disengagement tracked the extent to which competing memories were forgotten; greater forgetting of competing memories was associated with a greater decline in demands on prefrontal cortex during target remembering. These findings indicate that, although forgetting can be frustrating, memory might be adaptive because forgetting confers neural processing benefits.
Figure Legend: A whole-brain regression analysis showed that memory suppression at test was predicted by repetition-related activation decreases in (a) left dorsal ACC (anterior cingulate) (b) right anterior VLPFC (ventrolateral prefrontal cortex) In the ACC and right VLPFC, high suppressors showed reliable decreases in activation from first to third retrieval practice trials, whereas low suppressors did not. High suppressors showed greater initial ACC activation than low suppressors, but comparable initial right VLPFC activation. (c) A whole-brain regression analysis showed that the repetition-related activation decline in the right DLPFC covaried with that in the ACC, showing a functional coupling between ACC and right DLPFC that specifically relates to changes in demands on cognitive control across retrieval repetitions.
Thursday, June 07, 2007
Huang and Shadmehr report an interesting study in J. Neurophysiol. "Evolution of Motor Memory During the Seconds After Observation of Motor Error." Here is their abstract:
When a movement results in error, the nervous system amends the motor commands that generate the subsequent movement. Here we show that this adaptation depends not just on error, but also on passage of time between the two movements. We observed that subjects learned a reaching task faster, i.e., with fewer trials, when the intertrial time intervals (ITIs) were lengthened. We hypothesized two computational mechanisms that could have accounted for this. First, learning could have been driven by a Bayesian process where the learner assumed that errors are the result of perturbations that have multiple timescales. In theory, longer ITIs can produce faster learning because passage of time might increase uncertainty, which in turn increases sensitivity to error. Second, error in a trial may result in a trace that decays with time. If the learner continued to sample from the trace during the ITI, then adaptation would increase with increased ITIs. The two models made separate predictions: The Bayesian model predicted that when movements are separated by random ITIs, the learner would learn most from a trial that followed a long time interval. In contrast, the trace model predicted that the learner would learn most from a trial that preceded a long time interval. We performed two experiments to test for these predictions and in both experiments found evidence for the trace model. We suggest that motor error produces an error memory trace that decays with a time constant of about 4 s, continuously promoting adaptation until the next movement.
Kitano reviews a new book in Nature (PDE of review here): How the Body Shapes the Way We Think: A New View of Intelligence. by Rolf Pfeifer & Josh Bongard, Bradford Books: 2006. A few clips:
...a chess computer, unlike a human, does not have a body to enable it to interact with its environment, for example. This distinction differentiates two views on intelligence. One view is that intelligence is independent of the body and is unaffected by its existence, shape and function. The other view is that intelligence is contained within a physical body and that the body shapes the mind, an idea often referred to as physical embodiment or the presence of a behaviour-based agent.The Pfeifer and Bongard book offers perspective on how artificial-intelligence and robotics researchers are dealing with the increasing recognition in the artificial-intelligence and robotics communities that the nature of the body significantly affects the mind, although it does not totally control it. The book focuses on artificial agents, but with a lot of inspiration from nature.
One salient difference between the intelligent agents discussed in this book and traditional artificial-intelligence systems, as represented by chess computers, is the contextual thickness of system behaviours. Many of the robotics systems discussed in the book can cope, at least to some extent, with changes in the expected environment, tasks and other assumed conditions, whereas chess computers and other traditional artificial-intelligence systems are usually extremely fragile when faced with even a small change in such conditions. Behaviour-based robots should be able to perform almost flawlessly if the size of road or unevenness of terrain deviates from the initial assumption. However, the results will be catastrophic if a chess computer is given a chess board with nine rows and columns, rather than eight, as they are tuned specifically for the existing rules of chess. Imagine a thought experiment on a chess game between a behaviour-based system and an existing chess computer. The chess computer would be unbeatable with the defined rules, but if the rules were modified the behaviour-based system may do better.
Robert Frank has a nice piece in the New York Times (PDF here) describing some recent sociology/economics articles. Why are there so many jokes about dumb blondes and athletes despite persuasive evidence that blondes and athletes are no less intelligent than others? First the dumb blonde joke:
A married couple were awakened by a call at 2 a.m. The wife, a blonde, picked up the phone, listened a moment and said, “How should I know, that’s 200 miles from here!” and hung up. Her husband asked, “Who was that?” She replied, “I don’t know; some woman wanting to know if the coast is clear.”Now the dumb athlete joke:
Two offensive linemen in a rented boat catch an unusually large number of trout in a secluded cove. As they start back to the marina, one reaches over with his felt-tip pen and marks an X on the starboard bow. “I want to make sure we can find this spot again tomorrow,” he explained. “Idiot,” his friend replied, “what makes you think we’ll get the same boat?”Actually the hypothesis that beauty (blondness is viewed as a positive characteristic in women) and brains to together is more likely:
(1) men generally place relatively greater emphasis on looks; (2) women generally place relatively greater emphasis on income and status. (3) more-intelligent men tend to achieve higher income and status; (4) both intelligence and physical attractiveness are traits with significant inheritable components...if both beauty and intelligence are inheritable, then the offspring of such unions will tend to display above-average values of both traits.So why the dumb blonde and athlete jokes?
If blondes are perceived as more attractive, then being blond may create valuable opportunities that do not require onerous investments in education and training. The dumb blonde stereotype may thus stem from the fact that blondes rationally choose to invest less than others in education and other forms of human capital.and,
...because gifted athletes enjoy many attractive social and employment opportunities that others do not, they may rationally choose to invest less, on average, in human capital.
The bottom line is that popular perceptions about the intelligence of blondes and athletes may stem more from the academic choices made by members of these groups and from choices that others make about them than from any innate differences in mental ability.
Although I don't usually mention physics and cosmology in this blog, I would recommend a rather fascinating piece by Dennis Overbye in the science section of the New York Times (PDF here) "The Universe, Expanding Beyond All Understanding." We know space is sprinkled from now to forever with galaxies rushing away from one another under the impetus of the Big Bang. Overbye discusses several pieces of work showing that:
If things keep going the way they are... in 100 billion years the only galaxies left visible in the sky will be the half-dozen or so bound together gravitationally into what is known as the Local Group, which is not expanding and in fact will probably merge into one starry ball...Unable to see any galaxies flying away, those astronomers will not know the universe is expanding and will think instead that they are back in the static island universe of Einstein...observers in our ‘island universe’ will be fundamentally incapable of determining the true nature of the universe...future cosmologists...will puzzle about why the visible universe seems to consist of six galaxies.Quote from cosmologist James Peebles at Princeton:
"I have the uneasy feeling that the U.S.A. is headed into asymptotic futility well before that."
In another example of how children have time windows of developmental plasticity and learning, Weikum et al. (PDF here) show that 4 to 6 month-old infants can discriminate languages (English from French) just from viewing silently presented articulations. By the age of 8 months, only bilingual (French-English) infants succeed at this task. This indicates that infants are prepared very early for visual language discrimination, but loose this ability once they begin to learn a single language. Through experience adults can regain this sensitivity, for they can use visual cues to discriminate between two languages if they know one of the languages.
Wednesday, June 06, 2007
Ehrsson et al. report an interesting extension of work on illusory feelings of body ownership:
The feeling of body ownership is a fundamental aspect of self-consciousness. The underlying neural mechanisms can be studied by using the illusion where a person is made to feel that a rubber hand is his or her own hand by brushing the person's hidden real hand and synchronously brushing the artificial hand that is in full view. Here we show that threat to the rubber hand can induce a similar level of activity in the brain areas associated with anxiety and interoceptive awareness (insula and anterior cingulate cortex) as when the person's real hand is threatened. We further show that the stronger the feeling of ownership of the artificial hand, the stronger the threat-evoked neuronal responses in the areas reflecting anxiety. Furthermore, across subjects, activity in multisensory areas reflecting ownership predicted the activity in the interoceptive system when the hand was under threat. Finally, we show that there is activity in medial wall motor areas, reflecting an urge to withdraw the artificial hand when it is under threat. These findings suggest that artificial limbs can evoke the same feelings as real limbs and provide objective neurophysiological evidence that the rubber hand is fully incorporated into the body. These findings are of fundamental importance because they suggest that the feeling of body ownership is associated with changes in the interoceptive systems.
Figure legend - Linear relationship between ownership and the anxiety responses in the bilateral anterior insula and bilateral ACC (circled). A regression analysis identified a significant relationship between the vividness ratings of the rubber-hand illusion obtained during the scans and the parameter estimates for the contrast between threat during ownership and threat during no ownership in left insula
Tuesday, June 05, 2007
Previous research, involving monetary rewards, found that limbic reward-related areas show greater activity when an intertemporal choice includes an immediate reward than when the options include only delayed rewards. In contrast, the lateral prefrontal and parietal cortex (areas commonly associated with deliberative cognitive processes, including future planning) respond to intertemporal choices in general but do not exhibit sensitivity to immediacy (McClure et al., 2004). The current experiments extend these findings to primary rewards (fruit juice or water) and time delays of minutes instead of weeks. Thirsty subjects choose between small volumes of drinks delivered at precise times during the experiment (e.g., 2 ml now vs 3 ml in 5 min). Consistent with previous findings, limbic activation was greater for choices between an immediate reward and a delayed reward than for choices between two delayed rewards, whereas the lateral prefrontal cortex and posterior parietal cortex responded similarly whether choices were between an immediate and a delayed reward or between two delayed rewards. Moreover, relative activation of the two sets of brain regions predicts actual choice behavior. A second experiment finds that when the delivery of all rewards is offset by 10 min (so that the earliest available juice reward in any choice is 10 min), no differential activity is observed in limbic reward-related areas for choices involving the earliest versus only more delayed rewards. We discuss implications of this finding for differences between primary and secondary rewards.
Beta and delta brain areas. fMRI data were fit with two regressors. A, The beta regressor identified those brain areas that are preferentially activated by choices involving a reward available at a 0 min delay. Brain areas that correlated with this regressor included a set of brain areas all closely linked with the mesolimbic dopamine system. These include the NAc, PCC, mOFC, and ACC.
Here is another example of a really smart bird, this time an urban crow. (I gave a another example, One Clever Raven, in a previous post.
Monday, June 04, 2007
We are getting closer to knowing the specific chemical pathways that underlie age extension, at least in nematodes. Similar pathways are found in yeast and higher animals..from the editor's summary in Nature:
Severe calorie restriction extends life-span in mice and other species, but how near-starvation can prolong life remained a mystery. Now at last, specific links between calorie restriction and longevity have been found in that workhorse of ageing research, the nematode C. elegans. Nicholas Bishop and Leonard Guarente find that dietary restriction activates transcription factor SKN-1 in ASI neurons in the head, which signal peripheral tissues to increase metabolic activity, a mechanism suggestive of the involvement of an endocrine system. Panowski et al. report that increased activity of PHA-4, a transcription factor found in the intestine and in a few cells in head and tail, is also essential for diet-restricted longevity. PHA-4 resembles mammalian Foxa transcription factors, which affect development and regulate fasting glucagon and glucose levels. Knowledge of such links raises the prospect of drugs to mimic the benefits of calorie restriction.
From the review by Antebi:
In response to dietary restriction, the activities of SKN-1 and PHA-4 gene-transcription factors increase (black arrows). Neuronal, but not intestinal, SKN-1 mediates longevity in response to reduced dietary intake, where it triggers the release of unidentified hormones (stars) from the pair of ASI neurons to increase mitochondrial activity throughout the body. The PHA-4 transcription factor may also induce hormonal production in the tissues where it is expressed — neurons, intestine and gonad.
Although 'personalities' such as boldness, aggressive behaviour and risk avoidance have been shown to exist in more than sixty animal species, from primates to ants, explaining their existence in terms of evolution has been a puzzle. Surely, evolution should not favour the maintenance of different personalities, but rather the convergence towards a single one. In a numerical life-history model, Wolf et al. show that the evolution of animal personalities, defined as consistent sets of behaviours shown in a variety of contexts, is related to an adaptive response to life-history trade-offs. In this model, decisions on trade-offs between current and future reproduction condition the response of individuals to risky situations, and this may be the basis for animal personalities and their maintenance in populations.In Wolf et al.'s model (from their abstract)
...some individuals put more emphasis on future fitness returns than others. Life-history theory predicts that such differences in fitness expectations should result in systematic differences in risk-taking behaviour. Individuals with high future expectations (who have much to lose) should be more risk-averse than individuals with low expectations. This applies to all kinds of risky situations, so individuals should consistently differ in their behaviour. By means of an evolutionary model we demonstrate that this basic principle results in the evolution of animal personalities. It simultaneously explains the coexistence of behavioural types, the consistency of behaviour through time and the structure of behavioural correlations across contexts. Moreover, it explains the common finding that explorative behaviour and risk-related traits like boldness and aggressiveness are common characteristics of animal personalities.
Saturday, June 02, 2007
I may figure out how to stop this from happening (if anyone out there knows how, please let me know), but as I add labels (keywords) to old posts, RSS and atom readers think they are new postings. This will be happening over the next period of time.
The new google search box works like gangbusters, bringing up all posts with the word(s) you enter. The old Technorati search box was useless. The labels on the right will give you an idea of the areas I find interesting and take you to relevant posts. This may be more non-techies want to know, but this blog now completely replaces my existing file systems. A PDF file or link to any article I might want to use is now obtained through the blog, no more storage of paper copies (three file drawers full, used for my book) or copies on my local hard drive apart from backups of the yahoo server that hosts dericbownds.net. My dericbownds.net website stays as it was, with professional and personal stuff, but MindBlog (mindblog.dericbownds.net) has now moved to the blogger servers.
Friday, June 01, 2007
Because I am upgrading my blogger setup to use labels (keywords) I'm having to assign a new URL to MindBlog.
The new URL is http://mindblog.dericbownds.net
If you have bookmarked the blog portion of my site directly, please update your bookmark to the above address.
If you have subscribed directly to my RSS Feed you will need to change the feed URL on your reader.
RSS feed: http://mindblog.dericbownds.net/rss.xml
Atom feed: http://mindblog.dericbownds.net/atom.xml
No changes needed if you have subscribed to my Blog through FeedBurner.
Please allow several days for the changes to my Blog to take full effect while I transition to the new format.
The editor's summary of an interesting paper in Nature by Gilmore et al.:
It is commonly assumed that young children need to master the logic of number systems before learning symbolic arithmetic. Now a trial using 5-year-old children suggests that in fact they have symbolic arithmetic knowledge before they have received any arithmetic instruction. The children are capable of solving symbolic addition and subtraction problems with large numbers, provided that only approximate sums and differences must be computed. These findings shed light on the numerical competences that come naturally to children, and suggest ways to enrich children's learning of mathematics.
Edward Grieg's "Wedding in Troldhaugen" ....(having just returned from my son's wedding in Mexico.)
A brief essay in The New Yorker by James Surowiecki on how technology designed to make our lives easier does just the opposite. Some clips:
Technology is supposed to make our lives easier, allowing us to do things more quickly and efficiently. But too often it seems to make things harder, leaving us with fifty-button remote controls, digital cameras with hundreds of mysterious features and book-length manuals, and cars with dashboard systems worthy of the space shuttle...feature creep is the product of the so-called internal-audience problem: the people who design and sell products are not the ones who buy and use them, and what engineers and marketers think is important is not necessarily what’s best for consumers...although consumers find overloaded gadgets unmanageable, they also find them attractive. It turns out that when we look at a new product in a store we tend to think that the more features there are, the better. It’s only once we get the product home and try to use it that we realize the virtues of simplicity...It seems odd that we don’t anticipate feature fatigue and thus avoid it. But, as numerous studies have shown, people are not, in general, good at predicting what will make them happy in the future. As a result, we will pay more for more features because we systematically overestimate how often we’ll use them. We also overestimate our ability to figure out how a complicated product works.