Thursday, February 28, 2013

Amygdala damage can make us more generous

From van Honk et al.:

Contemporary economic models hold that instrumental and impulsive behaviors underlie human social decision making. The amygdala is assumed to be involved in social-economic behavior, but its role in human behavior is poorly understood. Rodent research suggests that the basolateral amygdala (BLA) subserves instrumental behaviors and regulates the central-medial amygdala, which subserves impulsive behaviors. The human amygdala, however, typically is investigated as a single unit. If these rodent data could be translated to humans, selective dysfunction of the human BLA might constrain instrumental social-economic decisions and result in more impulsive social-economic choice behavior. Here we show that humans with selective BLA damage and a functional central-medial amygdala invest nearly 100% more money in unfamiliar others in a trust game than do healthy controls. We furthermore show that this generosity is not caused by risk-taking deviations in nonsocial contexts. Moreover, these BLA-damaged subjects do not expect higher returns or perceive people as more trustworthy, implying that their generous investments are not instrumental in nature. These findings suggest that the human BLA is essential for instrumental behaviors in social-economic interactions.
Here is the anatomical location of the human lesions:

MR images (coronal view) of the three subjects with Urbach–Wiethe disease (UWD), with their year of birth and red crosshairs indicating the calcified brain damage...the lesions of the three patients are located in the BLA...the functional method shows activation during emotion matching in the superficial amygdala (SFA) and CMA, but not in the BLA.

Wednesday, February 27, 2013

How our viscera influence our brain and behavior

I want to pass on this fascinating and useful open source review by Critchley and Harrison in the journal Neuron. Having just had the flu, I found their presentation of visceral regulation of sickness behaviors very relevant! The article is worthwhile especially for the summary figures showing functional and anatomical pathways. (I resist the urge to paste them into this post, you can look at them by clicking on the link above. Here is their abstract:

Mental processes and their neural substrates are intimately linked to the homeostatic control of internal bodily state. There are a set of distinct interoceptive pathways that directly and indirectly influence brain functions. The anatomical organization of these pathways and the psychological/behavioral expressions of their influence appear along discrete, evolutionarily conserved dimensions that are tractable to a mechanistic understanding. Here, we review the role of these pathways as sources of biases to perception, cognition, emotion, and behavior and arguably the dynamic basis to the concept of self.
And, two clips from the text:
The internal state of the body motivates our desire to walk in the shade on a warm summer’s day and inhibits the desire to eat or socialize when feeling off-color. Communication from the viscera to brain is continuous and pervasive, yet we rarely give it a second thought. Visceral fluctuations and reactions accessible to introspective appraisal represent only the visible tip of the iceberg.
A comprehensive understanding of the integration of internal bodily signals in health is ultimately required for effective management of physical and psychological symptoms in illness. Such a goal can only be achieved through coordinated experimental approaches and perhaps a move away from treating physiological changes as irrelevant confounds in neuropsychological experiments. Together, these observations make “us realize more deeply than ever how much of our mental life is knit up in our corporeal frame” (James, 1890).

Tuesday, February 26, 2013

How ambient light might influence our mood.

The visual pigment melanopsin in the intrinsically photosensitive retinal ganglion cells (ipRGCs) of our inner retinas (two cells layers away from our rods and cones) detect ambient light and send this information to brain areas that regulate circadian rhythms and mood. LaGates et al. have now found that inappropriately timed light exposure that does not alter normal sleep architecture and circadian rhythmicity of body temperature and general activity still can cause impaired learning and depression-like behaviors in mice. In mice genetically altered to remove ipRGC cells, the depressive-like behaviors and learning deficits are not observed. If similar mechanisms operate in us humans, this suggests a potential mechanism by which abnormal ambient light schedules — caused by shift work or simply switching on an artificial light — might influence mood and learning. Here is their abstract:

The daily solar cycle allows organisms to synchronize their circadian rhythms and sleep–wake cycles to the correct temporal niche. Changes in day-length, shift-work, and transmeridian travel lead to mood alterations and cognitive function deficits. Sleep deprivation and circadian disruption underlie mood and cognitive disorders associated with irregular light schedules. Whether irregular light schedules directly affect mood and cognitive functions in the context of normal sleep and circadian rhythms remains unclear. Here we show, using an aberrant light cycle that neither changes the amount and architecture of sleep nor causes changes in the circadian timing system, that light directly regulates mood-related behaviours and cognitive functions in mice. Animals exposed to the aberrant light cycle maintain daily corticosterone rhythms, but the overall levels of corticosterone are increased. Despite normal circadian and sleep structures, these animals show increased depression-like behaviours and impaired hippocampal long-term potentiation and learning. Administration of the antidepressant drugs fluoxetine or desipramine restores learning in mice exposed to the aberrant light cycle, suggesting that the mood deficit precedes the learning impairments. To determine the retinal circuits underlying this impairment of mood and learning, we examined the behavioural consequences of this light cycle in animals that lack intrinsically photosensitive retinal ganglion cells. In these animals, the aberrant light cycle does not impair mood and learning, despite the presence of the conventional retinal ganglion cells and the ability of these animals to detect light for image formation. These findings demonstrate the ability of light to influence cognitive and mood functions directly through intrinsically photosensitive retinal ganglion cells.

Monday, February 25, 2013

The lament of the historian…

My colleague William Cronon at the University of Wisconsin was President of the American Historical Association for 2012,  and I want to pass on a clip from the AHA Presidential Address he delivered in Jan. 2013.  Among his concerns about the future of historical studies as a discipline is the digital revolution and internet that are transforming literally everything about the way historians work and how people read:

One of my deepest fears about this brave new digital world has to do with reading itself...It seems to me that the book-length monograph on which our discipline has long relied is very much at risk as texts migrate from paper to screens. It is not just that libraries are reducing purchases, that university presses are facing cutbacks, or that declining print runs and rising per-unit costs are pricing many specialized monographs beyond the reach of ordinary buyers. My deeper fear comes from watching my own students, many of whom no longer read books for pleasure. If they have any prior experience doing research, almost all of it is online. If a piece of information cannot be Googled, it effectively does not exist for them. More than a few of my students have never actually been inside the stacks of a library. To the extent that good writing is predicated on frequent skilled reading, the ability of such students to recognize and construct grammatical sentences and paragraphs—let alone graceful or elegant ones—is plummeting.
In a manically multitasking world where even e-mail takes too long to read, where texts and tweets and Facebook postings have become dominant forms of communication, reading itself is more at risk than many of us realize. Or, to be more precise, long-form reading is at risk: the ability to concentrate and sustain one's attention on arguments and narratives for many hours and many thousands of words. I have come to think of this as the Anna Karenina problem: will students twenty years from now be able to read novels like Tolstoy's that are among the greatest works of world literature but that require dozens of hours to be meaningfully experienced? And if a novel as potent as Anna lies beyond reach, what does that imply for complex historical monographs that are in many ways even more challenging in the demands they make on readers?
What is the future of history?...there is one answer that is arguably the most basic of all, and that is, simply: storytelling. We need to remember the roots of our discipline and be sure to keep telling stories that matter as much to our students and to the public as they do to us. Although the shape and form of our stories will surely change to meet the expectations of this digital age, the human need for storytelling is not likely ever to go away. It is far too basic to the way people make sense of their lives—and among the most important stories they tell are those that seek to understand the past. Hang on to this truth, and there is no reason to fear that history will be any less important to the human future than it has been to the human past.

Friday, February 22, 2013

In an uncertain world, fairness finishes first.

I usually get hopelessly lost in accounts of variations of the ultimatum game used to model human behavior and its evolutionary rationale or origins. This experiment by Rand et al. seems relatively clear and crisp:

Classical economic models assume that people are fully rational and selfish, while experiments often point to different conclusions. A canonical example is the Ultimatum Game: one player proposes a division of a sum of money between herself and a second player, who either accepts or rejects. Based on rational self-interest, responders should accept any nonzero offer and proposers should offer the smallest possible amount. Traditional, deterministic models of evolutionary game theory agree: in the one-shot anonymous Ultimatum Game, natural selection favors low offers and demands. Experiments instead show a preference for fairness: often responders reject low offers and proposers make higher offers than needed to avoid rejection. Here we show that using stochastic evolutionary game theory, where agents make mistakes when judging the payoffs and strategies of others, natural selection favors fairness. Across a range of parameters, the average strategy matches the observed behavior: proposers offer between 30% and 50%, and responders demand between 25% and 40%. Rejecting low offers increases relative payoff in pairwise competition between two strategies and is favored when selection is sufficiently weak. Offering more than you demand increases payoff when many strategies are present simultaneously and is favored when mutation is sufficiently high. We also perform a behavioral experiment and find empirical support for these theoretical findings: uncertainty about the success of others is associated with higher demands and offers; and inconsistency in the behavior of others is associated with higher offers but not predictive of demands. In an uncertain world, fairness finishes first.

Thursday, February 21, 2013

Big brains decrease fertility.

More intelligent mammals, such as humans, whales, and dolphins, have decreased fertility. One ideas has been that the energetic cost of increased brain power has been meet by decreasing the size of the gut and decreasing reproductive function. Kotrschal et al. have tested this idea by selecting for brain size in guppies and obtaining populations of fish whose brains were larger or smaller than normal and differed from one another by about 10%. The cost of the increased brain power was a decrease in the size of the gut and a decrease in reproductive function. Here is their abstract:

The large variation in brain size that exists in the animal kingdom has been suggested to have evolved through the balance between selective advantages of greater cognitive ability and the prohibitively high energy demands of a larger brain (the “expensive-tissue hypothesis”). Despite over a century of research on the evolution of brain size, empirical support for the trade-off between cognitive ability and energetic costs is based exclusively on correlative evidence, and the theory remains controversial. Here we provide experimental evidence for costs and benefits of increased brain size. We used artificial selection for large and small brain size relative to body size in a live-bearing fish, the guppy (Poecilia reticulata), and found that relative brain size evolved rapidly in response to divergent selection in both sexes. Large-brained females outperformed small-brained females in a numerical learning assay designed to test cognitive ability. Moreover, large-brained lines, especially males, developed smaller guts, as predicted by the expensive-tissue hypothesis, and produced fewer offspring. We propose that the evolution of brain size is mediated by a functional trade-off between increased cognitive ability and reproductive performance and discuss the implications of these findings for vertebrate brain evolution.

Wednesday, February 20, 2013

How mindfulness meditation works in the brain - a model

Kerr et al make some interesting speculations. Their article contains some useful summary graphics.

Using a common set of mindfulness exercises, mindfulness based stress reduction (MBSR) and mindfulness based cognitive therapy (MBCT) have been shown to reduce distress in chronic pain and decrease risk of depression relapse. These standardized mindfulness (ST-Mindfulness) practices predominantly require attending to breath and body sensations. Here, we offer a novel view of ST-Mindfulness's somatic focus as a form of training for optimizing attentional modulation of 7–14 Hz alpha rhythms that play a key role in filtering inputs to primary sensory neocortex and organizing the flow of sensory information in the brain. In support of the framework, we describe our previous finding that ST-Mindfulness enhanced attentional regulation of alpha in primary somatosensory cortex (SI). The framework allows us to make several predictions. In chronic pain, we predict somatic attention in ST-Mindfulness “de-biases” alpha in SI, freeing up pain-focused attentional resources. In depression relapse, we predict ST-Mindfulness's somatic attention competes with internally focused rumination, as internally focused cognitive processes (including working memory) rely on alpha filtering of sensory input. Our computational model predicts ST-Mindfulness enhances top-down modulation of alpha by facilitating precise alterations in timing and efficacy of SI thalamocortical inputs. We conclude by considering how the framework aligns with Buddhist teachings that mindfulness starts with “mindfulness of the body.” Translating this theory into neurophysiology, we hypothesize that with its somatic focus, mindfulness' top-down alpha rhythm modulation in SI enhances gain control which, in turn, sensitizes practitioners to better detect and regulate when the mind wanders from its somatic focus. This enhanced regulation of somatic mind-wandering may be an important early stage of mindfulness training that leads to enhanced cognitive regulation and metacognition.

Tuesday, February 19, 2013

Interdependent behavior facilitated by independent behavior?

Hamedani et al. , who end up suggesting that it may be necessary to invoke independent behaviors in order to successfully motivate interdependence, start their article with a Quote:

"Each time I look at that flag, I’m reminded that our destiny is stitched together like those 50 stars and those 13 stripes . . . And if we hold fast to that truth, in this moment of trial, there is no challenge too great." "—U.S. president Barack Obama, State of the Union address, January 24, 2012 "
They then outline the context for their study on factors that influence the kinds of interdependent behavior needed to face problems common to all people, such as the environmental crisis. They:
...compared European Americans, who have been exposed primarily to mainstream cultural contexts that promote and value independence, with East Asian Americans, who have been exposed both to these contexts and also to cultural contexts that promote and value interdependence. Asian Americans are considered bicultural because they are exposed not only to mainstream American contexts that foster independent behavior (e.g., in schools and workplaces), but also to East Asian contexts that foster interdependent behavior (e.g., in families and communities)...This European American/Asian American cultural contrast allowed us to examine whether independence necessarily functions as a barrier to interdependent awareness and action. Comparing two American groups who are similar in their exposure to independence but different in their exposure to interdependence enabled us to test the theory that interdependence may undermine motivation because of a lack of exposure to cultural contexts that promote and value it as a normatively “good” style of behavior.1 Specifically, we tested the hypothesis that invoking interdependent behavior, compared with invoking independent behavior, would undermine motivation for European Americans but not for bicultural Asian Americans.
Here is their abstract:
Today’s most pressing social challenges require people to recognize their shared fate and work together—to think and act interdependently. In the three studies reported here, we found that appeals for increased interdependence may undermine the very motivation they seek to inspire. We examined the hypothesis that invoking interdependent action undermines motivation for chronically independent European Americans but not for bicultural Asian Americans who are both chronically independent and chronically interdependent. Two studies demonstrated that priming interdependent rather than independent action undermined European Americans’ motivation to perform challenging mental and physical tasks. A third study showed that framing an appeal for environmental sustainability in terms of interdependent rather than independent action led to decreased motivation and resource allocation among European Americans. Motivation was not undermined for Asian Americans, which reveals how behavior is divergently shaped, in the land of the free, by foundational sociocultural schemas of independence and interdependence. This research has the novel implication that it may be necessary to invoke independent behaviors in order to successfully motivate interdependence.

Monday, February 18, 2013

Red Brain, Blue Brain

Darren Schreiber and collaborators add yet another article to what is a growing literature on the differing sensitivities to threat of liberals and conservatives. Their open access article shows brain imaging and behavioral correlates. It seems likely not only that having a particular brain would influence our political views, but also that having a particular political view would influence and change our brains. The causal arrow seems likely to run in both directions—which would make sense in light of what we know about the plasticity of the brain.

Liberals and conservatives exhibit different cognitive styles and converging lines of evidence suggest that biology influences differences in their political attitudes and beliefs. In particular, a recent study of young adults suggests that liberals and conservatives have significantly different brain structure, with liberals showing increased gray matter volume in the anterior cingulate cortex, and conservatives showing increased gray matter volume in the in the amygdala. Here, we explore differences in brain function in liberals and conservatives by matching publicly-available voter records to 82 subjects who performed a risk-taking task during functional imaging. Although the risk-taking behavior of Democrats (liberals) and Republicans (conservatives) did not differ, their brain activity did. Democrats showed significantly greater activity in the left insula, while Republicans showed significantly greater activity in the right amygdala. In fact, a two parameter model of partisanship based on amygdala and insula activations yields a better fitting model of partisanship than a well-established model based on parental socialization of party identification long thought to be one of the core findings of political science. These results suggest that liberals and conservatives engage different cognitive processes when they think about risk, and they support recent evidence that conservatives show greater sensitivity to threatening stimuli.

Friday, February 15, 2013

Chimps play fair in the ultimatum game.

These interesting observations by Proctor, de Waal et al. using a new experimental design that resolves conflicting data in studies by other authors suggest that our human sense of fairness has an early origin in primate behavior.

Is the sense of fairness uniquely human? Human reactions to reward division are often studied by means of the ultimatum game, in which both partners need to agree on a distribution for both to receive rewards. Humans typically offer generous portions of the reward to their partner, a tendency our close primate relatives have thus far failed to show in experiments. Here we tested chimpanzees (Pan troglodytes) and human children on a modified ultimatum game. One individual chose between two tokens that, with their partner’s cooperation, could be exchanged for rewards. One token offered equal rewards to both players, whereas the other token favored the chooser. Both apes and children responded like humans typically do. If their partner’s cooperation was required, they split the rewards equally. However, with passive partners—a situation akin to the so-called dictator game—they preferred the selfish option. Thus, humans and chimpanzees show similar preferences regarding reward division, suggesting a long evolutionary history to the human sense of fairness.

Thursday, February 14, 2013

How we listen to music...

Adam Gopnik has a very nice essay in The New Yorker on the mysteries of sound and the quest for 3-D recording. I was struck by his description of how the way we listen to music has changed. (I sometimes think with nostalgia about growing up in a 1950's household where "Hi Fidelity" was taken very seriously, trying as closely as possible to re-create the experience in the concert hall. Good old analog vinyl records played on mechanically sophisticated turntables with fancy diamond needles tracking the grooves, state of the art amplifiers, and speakers.... And now I have the best quality wireless speaker one can get, but it still must depend entirely on the compressed audio computer file formats such as .mp3 or.aiff, that throw away the richness I used to know.) His comments on how the music listening of his teen-age kids has changed, they:

...have an entirely different way of listening. They ignore the glowing-tube amp and classy articulate speakers in our living room; they bounce instead to tinny earbuds, and often spend hours listening to Taylor Swift or Radiohead on the still more tinny speakers of their computers. Sound quality seems secondary to some other thing they take from music...they have a more limited conception of larger forms, of the... of the symphony's three or four parts, of the swell and structure of a cantata. It isn't a question of classical tastes against pop; it's a question of small forms heard in motion against large form heard with solemn intent. "Sgt. Pepper: baffles them as much as Beethoven's Ninth. They snatch at music as we snatched at movies, filling our heads with plural images.
Gopnik's article presents fascinating interviews with current music researchers, from engineers like Edgar Choueiri to brain scientists such as Zatorre and Levitin at McGill University in Montreal. (MindBlog has several posts on their work.)

Wednesday, February 13, 2013

Internal threats to our bodies trigger different fear system from external threats.

A large volume of work has documented the amygdala's role in fear, and now Feinstein et al. present a surprising finding that carbon dioxide inhalation evokes fear and panic in three patients with bilateral amygdala damage (who feel no fear from external threats). These results indicate that the amygdala is not required for fear triggered internally rather than by external threats.  Here is the abstract:

Decades of research have highlighted the amygdala's influential role in fear. We found that inhalation of 35% CO2 evoked not only fear, but also panic attacks, in three rare patients with bilateral amygdala damage. These results indicate that the amygdala is not required for fear and panic, and make an important distinction between fear triggered by external threats from the environment versus fear triggered internally by CO2.

Why do these 'fearless' patients feel fear when CO2 levels in their blood are increased? The authors suggest:
...that all of these other stimuli were exteroceptive in nature, mainly processed through visual and auditory pathways that project to the amygdala. In contrast, CO2 acts internally at acid-activated chemoreceptors and causes an array of physiological changes. Thus, CO2 might engage interoceptive afferent sensory pathways that project to the brainstem, diencephalon and insular cortex. In addition, many brain areas outside the amygdala possess CO2 and pH-sensitive chemoreceptors, including acid-sensing ion channels. Thus, CO2 may directly activate extra-amygdalar brain structures that underlie fear and panic, which may help to explain the apparent discrepancy between these findings and previous work in mice. In either case, our results indicate that, in humans, the internal threat signaled by CO2 is detected and interpreted as fear and panic despite the absence of an intact amygdala.

Tuesday, February 12, 2013

Wisconsin Public Radio series on consciousness

I've been wanting to point to an engaging series of interviews on consciousness presented by Wisconsin Public Radio either for listening, or in transcript form.  A wide range of philosophers, scientists, and new age gurus are engaged, including Marvin Minsky, Roger Penrose, Daniel Dennett, Alva Noe, Susan Blackmore, David Chalmers, Christof Koch, Guilio Tononi,  Stanislav Grof, Michael Gazzaniga, Depak Chopra, V.S. Ramachandran, Oliver Sacks, and many others.  It's quite an amazing and extensive list.   

Monday, February 11, 2013

We can retroactively edit our conscious experience.

Have you ever had the experience of tuning out someone who was droning on in a conversation or lecture that was boring you, then when suddenly being challenged by "Are you listening, what did I just say?," being surprised that you could summon up some recall of what they said, even though you had been completely ignoring it? This would be an example of how our perceptions and our consciousness can be two different things. We experience time very differently from what it really is, subjective and objective time are not the same. Our consciousness is more than just a movie that's playing in your head that you see once the processing is done. For example, recent work from Sergent and collaborators suggests that we can go back in time for at least a half a second and reintegrate something into our experience that we had previously ignored. From a review by Tia Ghose:

Study participants were shown groups of lines appearing in a circle on either the right or the left side of the screen before they disappeared. Sometimes the lines were too faint to consciously notice, while other times they were very obvious. In some of the trials where the lines were very faint, the researchers drew participants' attention to the spot where the lines had been by briefly dimming the circle — creating more contrast between the circle and the background. That "cueing of attention" happened up to a half-second after the lines disappeared. Afterward, the team asked the students what they saw. When the team had drawn attention to the spot where the lines had been, people were more likely to report having seen them "quite well." In essence, the participants had experienced retro-perception, the bizarre experience in which their brains added the lines to their conscious memory after the lines had disappeared.
Here is the Sergent et al. abstract:
Is our perceptual experience of a stimulus entirely determined during the early buildup of the sensory representation, within 100 to 150 ms following stimulation? Or can later influences, such as sensory reactivation, still determine whether we become conscious of a stimulus? Late visual reactivation can be experimentally induced by postcueing attention after visual stimulus offset [5]. In a contrary approach from previous work on postcued attention and visual short-term memory, which used multiple item displays [6 and 7], we tested the influence of postcued attention on perception, using a single visual stimulus (Gabor patch) at threshold contrast. We showed that attracting attention to the stimulus location 100 to 400 ms after presentation still drastically improved the viewers’ objective capacity to detect its presence and to discriminate its orientation, along with drastic increase in subjective visibility. This retroperception effect demonstrates that postcued attention can retrospectively trigger the conscious perception of a stimulus that would otherwise have escaped consciousness. It was known that poststimulus events could either suppress consciousness, as in masking, or alter conscious content, as in the flash-lag illusion. Our results show that conscious perception can also be triggered by an external event several hundred ms after stimulus offset, underlining unsuspected temporal flexibility in conscious perception.

Friday, February 08, 2013

Deric Bownds' MindBlog - 7th Anniversary

I just realized that today, 7 years ago on Feb. 8, 2006, was my first posting on this blog, which I started after reading a New York Times article on the emerging blogging craze. Now, 3,024 posts later, I'm sort of incredulous that it has stayed around so long. It appears, from Feedburner monitoring that has been going on since June of 2006, that there are now about 2,500 subscribers to MindBlog's feed, there are an average of ~380 significant engagements of readers with the blog every day, and there have been a total of about 1.5 million views. The paste in below shows postings that have received with most views. Just keeping up with MindBlog maintenance is a bit of effort. Every week 3-4 emails come in requesting quest postings or cross links, or offering revenue opportunities. My cut and paste boilerplate response: "I find that I'm receiving a large number of similar requests,  and have a policy of entering on my site only content that I initiate.   I have no commercial links on the site and am uninterested in revenue." 

I must apologize if your comments do not appear immediately, but I've been forced to start reviewing them again to weed out those that are are platitudes with links to commercial sites - they  now outnumber legitimate comments. 

About this time every year I have an identity crisis over whether I should continue the blog and/or develop a next lecture/essay topic, and/or write a book, spend more time with my piano...or just lie in the sun a bit more...  I usually just keep plugging along doing what I have been doing... Soon to be 71 years old, I find the motivation to change my habits declining.  And,  I am gratified by the occasional "thank you for the blog"  email that I get. 

Thursday, February 07, 2013

The cocktail party effect is enhanced by vision.

Golumbic et al. show that watching someone we are trying to hear and understand in a crowded noisy setting sharpens up the auditory processing in our brains that suppresses unwanted sounds from our surround:

Our ability to selectively attend to one auditory signal amid competing input streams, epitomized by the “Cocktail Party” problem, continues to stimulate research from various approaches. How this demanding perceptual feat is achieved from a neural systems perspective remains unclear and controversial. It is well established that neural responses to attended stimuli are enhanced compared with responses to ignored ones, but responses to ignored stimuli are nonetheless highly significant, leading to interference in performance. We investigated whether congruent visual input of an attended speaker enhances cortical selectivity in auditory cortex, leading to diminished representation of ignored stimuli. We recorded magnetoencephalographic signals from human participants as they attended to segments of natural continuous speech. Using two complementary methods of quantifying the neural response to speech, we found that viewing a speaker's face enhances the capacity of auditory cortex to track the temporal speech envelope of that speaker. This mechanism was most effective in a Cocktail Party setting, promoting preferential tracking of the attended speaker, whereas without visual input no significant attentional modulation was observed.
These neurophysiological results underscore the importance of visual input in resolving perceptual ambiguity in a noisy environment. Since visual cues in speech precede the associated auditory signals, they likely serve a predictive role in facilitating auditory processing of speech, perhaps by directing attentional resources to appropriate points in time when to-be-attended acoustic input is expected to arrive.

Wednesday, February 06, 2013

Aging, sleep, and memory.

Events during a day that we think important to remember are held in short term memory storage by an active hippocampus. Then, during deep, non-REM, slow brain wave sleep, enhanced connectivity between the hippocampus and frontal cortex cortex allow transfer of the information to long term storage in frontal and temporal lobes. It is also know that the duration of this deep sleep diminishes as our frontal lobes diminish in size (atrophy) with aging. Mandor et al., in worked pointed to in an article by Benedict Carey, have done an interesting study suggesting that the interaction of these factors represents a neuropatholgical pathway associated with cognitive decline in later life. Here is their abstract:

Aging has independently been associated with regional brain atrophy, reduced slow wave activity (SWA) during non–rapid eye movement (NREM) sleep and impaired long-term retention of episodic memories. However, whether the interaction of these factors represents a neuropatholgical pathway associated with cognitive decline in later life remains unknown. We found that age-related medial prefrontal cortex (mPFC) gray-matter atrophy was associated with reduced NREM SWA in older adults, the extent to which statistically mediated the impairment of overnight sleep–dependent memory retention. Moreover, this memory impairment was further associated with persistent hippocampal activation and reduced task-related hippocampal-prefrontal cortex functional connectivity, potentially representing impoverished hippocampal-neocortical memory transformation. Together, these data support a model in which age-related mPFC atrophy diminishes SWA, the functional consequence of which is impaired long-term memory. Such findings suggest that sleep disruption in the elderly, mediated by structural brain changes, represents a contributing factor to age-related cognitive decline in later life.

Tuesday, February 05, 2013

Racial essentialism correlates with less domain-general creativity.

Interesting observations from a group at Tel Aviv University:

Individuals who believe that racial groups have fixed underlying essences use stereotypes more than do individuals who believe that racial categories are arbitrary and malleable social-political constructions. Would this essentialist mind-set also lead to less creativity? We suggest that the functional utility derived from essentialism induces a habitual closed-mindedness that transcends the social domain and hampers creativity. Across studies, using both individual difference measures (in a pilot test) and experimental manipulations, we found that an essentialist mind-set is indeed hazardous for creativity, with the relationship mediated by motivated closed-mindedness. These results held across samples of majority cultural-group members (Caucasian Americans, Israelis) and minority-group members (Asian Americans), as well as across different measures of creativity (flexibility, association, insight). Our findings have important implications for understanding the connection between racial intolerance and creativity.
Some details: Participants in the study were primed by reading an article that vividly described fictitious scientific research supporting either racial essentialist or nonessentialist beliefs, respectively. (Work by others had established the effectiveness of these articles in activating racial essentialism or nonessentialism mind-sets). A control group read neither article. Then, in an ostensibly unrelated research project, they measured creativity in the three conditions using the Remote Associates Test (RAT). This task, which assesses participants’ ability to form a new combination that links mentally distant associative elements, requires identifying a single target word that is strongly associated with three distinct stimulus words (e.g., given the words “manners,” “round,” and “tennis,” the correct answer would be “table”). Their experiment suggesting closed-mindedness as the mediator of the essentialism-creativity link used the same priming procedure and assayed insight creativity using the Duncker candle problem, in which participants have to figure out how — using only a candle, a pack of matches, and a box containing tacks — they can attach the candle to a wall so that the candle burns properly without dripping wax on the table or floor. (The correct solution requires the ability to relax preexisting assumptions about functions of the items and use the box of tacks as a candleholder.)

Monday, February 04, 2013

"Chasing Ice" - watching a glacier calving

 I have to pass on this amazing video shared by Wisconsin colleague John Young, showing one of the breakdowns of a glacier that has retreated as much in the past 10 years as in the previous 100 years:

Early musical training - sensitive period in brain white matter plasticity

MindBlog has noted a number of studies that document beneficial effects of early music training on adult brain function. Now Steele and collaborators make observations that may partially explain why musicians such as Yo-Yo Ma, Oscar Peterson, and Pablo Casals, who all began training in early childhood before the age of 7 years, are so highly skilled. The authors examine the bundle of nerve fibers, the corpus callosum, that links our two cerebral hemispheres. Playing a musical instrument requires the coordinated action of the two hands and interhemispheric interactions mediated by the corpus callosum have been shown to play a prominent role in bimanual coordination. They measure the connectivity of this nerve fiber bundle using MRI. Edited from their introduction:

...there may be a sensitive period when early musical training has greater effects on the brain and behavior than training later in life...A sensitive period is defined as a developmental window where experience has long-lasting effects on the brain and behavior ...studies in animals show that exposure or training during specific periods in development can produce enhanced structural and functional plasticity in visual, auditory, and somatosensory regions of the brain...Evidence for sensitive periods in humans comes from studies of second language learning showing that early exposure results in greater proficiency, studies of deaf children showing that receiving cochlear implants earlier results in better language development, and studies of blind persons showing greater neuronal reorganization following early blindness.
Musicians are an excellent model for investigating possible sensitive period effects on brain and behavior, as training often begins early and is quantifiable...Evidence for a possible sensitive period for musical training came from a study showing that the anterior corpus callosum (CC) was larger in musicians than non-musicians, and that the difference was greater for those who began training before the age of 7 years...However, none of these studies controlled for the fact that musicians who begin earlier typically have more training than those who begin later.
Here is their abstract:
Training during a sensitive period in development may have greater effects on brain structure and behavior than training later in life. Musicians are an excellent model for investigating sensitive periods because training starts early and can be quantified. Previous studies suggested that early training might be related to greater amounts of white matter in the corpus callosum, but did not control for length of training or identify behavioral correlates of structural change. The current study compared white-matter organization using diffusion tensor imaging in early- and late-trained musicians matched for years of training and experience. We found that early-trained musicians had greater connectivity in the posterior midbody/isthmus of the corpus callosum and that fractional anisotropy in this region was related to age of onset of training and sensorimotor synchronization performance. We propose that training before the age of 7 years results in changes in white-matter connectivity that may serve as a scaffold upon which ongoing experience can build.

Friday, February 01, 2013

The promise and perils of oxytocin.

Greg Miller summarizes some consequences of recent work showing that oxytocin promotes trust and cooperation, and makes people more attuned to social cues.  It has some not so sweet aspects also.  He mentions a number of the studies I've cited in previous mindblog posts (just enter oxytocin in the search box in the left column to display them):

Now psychiatrists have caught oxytocin fever...Many psychiatric conditions have social symptoms, such as the characteristic lack of empathy in autism, the attachment anxiety of borderline personality disorder, and the paranoia of schizophrenia. Yet no drugs currently approved for psychiatric use directly target social behavior...But as researchers have continued to explore the hormone's effect on human behavior, a darker side has emerged. Oxytocin seems to promote aggression or other antisocial behavior in some circumstances. Its effects also appear to vary depending on a person's genetic makeup and psychological status. And no one knows what long-term oxytocin treatment does to the developing human brain. Disconcertingly, one recent study found that male voles treated for several weeks with oxytocin nasal spray around the time of adolescence later exhibited impaired social bonding with females... thus, there is concern about giving oxytocin to children before more is known about the hormone's developmental effects.
...the more recent oxytocin research in humans has frequently found its way into tabloids. In one of the first eye-catching studies in 2005 students who got oxytocin were more trusting...A torrent of studies followed, suggesting that oxytocin not only increases trust and cooperation, but also boosts social perceptiveness, such as face recognition and the ability to read what's on someone's mind from the look in their eyes.
A number of clinical trials suggest oxytocin causes a modest improvement in children and adults with autism, also in social behavior of psychotic patients, but reservations are raised by the vole studies showing early administration of oxytocin disturbs adult bonding and reproductive behavior, and by human studies showing that while it increases altruistic behavior towards in-group individuals, it increases aggression towards out group people.