The Neurobiology of Play

Taking Play Seriously, by Robin Marantz Henig, appears today in the New York Times Magazine.  Henig draws on ethology, neuroscience, and developmental psychology to highlight advances in research on play.  Play strikes many of us as deeply essential, but what the heck is it for?  It’s not precisely clear. 

Today I’ll cover some of the interesting developments about the neurobiology of play mentioned in Taking Play Seriously.  So John Byers first.  Byers is a zoologist at the University of Idaho who noticed that the developmental trajectory of play looks like an inverted U across many species, increasing during the juvenile period and dropping off during puberty.  This pattern corresponded quite well with the growth curve of the cerebellum.  The article summarizes the implications: 

The synchrony suggested a few things to Byers: that play might be related to growth of the cerebellum, since they both peak at about the same time; that there is a sensitive period in brain growth, during which time it’s important for an animal to get the brain-growth stimulation of play; and that the cerebellum needs the whole-body movements of play to achieve its ultimate configuration.

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Thinking about how others think: two ways?

Blogging on Peer-Reviewed ResearchJason Mitchell and Mahzarin R. Banaji, of Harvard University, and C. Neil Macrae, at the University of Aberdeen, published a fascinating piece in Neuron in May 2006, ‘Dissociable Medial Prefrontal Contributions to Judgments of Similar and Dissimilar Others’ (abstract on PubMed or pdf download here). I came across the article through the Mind Matters blog in a piece by Stephen Macknik (director of the Laboratory of Behavioral Neurophysiology at the Barrow Neurological Institute in Phoenix), entitled How Harvard students perceive rednecks: The neural basis for prejudice. Both the original article and the blog post by Macknik are worth checking out.

In the experiment, the team headed by Mitchell showed the subjects photographs and asked the subjects questions about the beliefs, feelings, or attitudes of the people in the pictures. Subjects were told the pictures were of either ‘liberal northeastern’ or ‘conservative Midwest fundamentalist Christian students’ after doing a survey which determined which group the subjects were most like. The categories for the photographs were false, the pictures being taken from dating websites and randomly assigned to either of the groups. The photos were reassigned for each subject, and gender, age and other distinguishing marks controlled for (or likely just avoided by the original choice of photos). In other words, college students were being told that other ‘college students’ were either ‘like them’ or ‘different from them,’ with (apparently) no visual cues for either identity. The research team was interested in what parts of the brain were being used in attempts to ‘mentalize,’ that is, to perceive the thoughts, motives or perceptions of others.

In particular, the researchers discussed that slightly different parts of the medial prefrontal cortex (mPFC) are used when trying to mentalize, depending upon whether the target of observation is believed to be similar or dissimilar (should I write ‘the Other’ to prove I’m a cultural anthropologist?) to the self. Specifically, a more ventral (front) part of mPFC is used when ‘mentalizing’ about others perceived as similar, as opposed to a higher (dorsal) part of the mPFC used to deduce the thinking or feelings of others when confronted with photos of people thought to be ‘unlike’ themselves. The difference is significant because the different regions suggest that these perceptions are being accomplished in distinct fashion.

… simulation theories of social cognition suggest that this [ventral] region should be specifically engaged for mental state inferences about others perceived to be similar to oneself, since mentalizing on the basis of self knowledge can only take place if another person’s internal experience is assumed to be comparable to one’s own. As such, this hypothesis suggests an important ‘‘division of labor’’ in the contributions made by different subregions of mPFC to mentalizing. Whereas ventral mPFC may be expected to contribute to mental state inferences about similar others, the dorsal [upper or top] aspects of mPFC—more traditionally associated with mentalizing tasks—should be specifically engaged by mentalizing about dissimilar others, that is, individuals for whom overlap between self and other cannot be assumed.

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Auditory neurons learning to hear

The Biotechnology and Biological Sciences Research Council’s recent business report (January 2008) had an interesting research report on auditory neurons and the perception of complex sounds. (Science Daily has a short report on the longer piece available here). (The BBSRC is the UK’s principal funder of basic biological research.)

As the BBSRC piece discusses, sound perception is extremely difficult because similar objects often make quite different sounds, and the medium (typically air) through which we hear does not allow for the spatialization or easy decomposition that, say, light allows in vision. The Oxford-based research team is using neural imaging to try to figure out how the brain makes sense of sound, and one thing that they’re finding is that background noise appears to be extremely important to sound processing. The auditory cortex does not simply respond to isolated qualities of specific sounds but to variations in the statistical properties of the entire sound scape. As the article reports: ‘Cortical neurons appear to anticipate this particular level of statistical regularity, and respond best to sounds that vary in pitch and intensity according to this natural rate of ebb and flow, which is found in many natural scenes and most musical compositions.’

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Visual Rewards

Blogging on Peer-Reviewed ResearchWhy will we study a favored painting again and again?  Or gaze on our lover’s face with such pleasure, even after years and lines have mounted?

 I came across an article, “Perceptual Pleasure and the Brain,” by Irving Biederman and Edward Vessel in American Scientist.  They studied the distribution of mu-opioid receptors, associated with the modulation of pleasure and pain, in the visual cortex.  Their basic result: “The receptors are sparsest in the early stages of this [central visual] pathway, the so-called V1 to V4 areas, where an image is processed as local bits of contour, color and texture.  Intermediate stages of visual processing, such as the lateral occipital area and ventral occipito-temporal cortex, which integrate local information to detect surfaces, objects, faces and places, contain greater number of opioid receptors.  The receptors are densest in the later stages of recognition, in the parahippocampal cortex and rhinal cortex, where visual information engages our memories.”

 Thus, they argue, “a visual stimulus that elicits many episodic or semantic memories should be more pleasing (or more interesting) than a stimulus that brings forth fewer mental associations.” 

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Pets, health and our extended phenotype

There’s a fun piece in The New York Times on The Healing Power of Dogs that discusses a wide range of health effects linked to pet ownership. The article briefly discusses a range of research that has linked pet ownership to health benefits. For example:

One Japanese study found pet owners made 30 percent fewer visits to doctors. A Melbourne study of 6,000 people showed that owners of dogs and other pets had lower cholesterol, blood pressure and heart attack risk compared with people who didn’t have pets. Obviously, the better health of pet owners could be explained by a variety of factors, but many experts believe companion animals improve health at least in part by lowering stress.

This research is fascinating in its own right, especially for a person who’s only recently started to live around animals… a lot of animals (at last count, 8 horses, 1 horse expecting a foal, 2 cats, 2 dogs, innumerable wild birds, kangaroos and wallabies all wandering onto the property). I’ve noticed a huge difference in my health and mood since the change, but it’s hard to separate the effects of having Basil and Roxy (the dogs), Glitz and Glam (the cats), or the bigger monkeys around (the horses). But the research discussed also touches on two issues that I think are of particular importance to those of us interested in neuroanthropology and the biology-culture interface.

Edited version
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Language and Color

Blogging on Peer-Reviewed ResearchEdge asked prominent scholars a great question, What Have You Changed Your Mind About?

 Lera Boroditsky, in Cognitive Psychology at Stanford, called her post, “Do our languages shape the nuts and bolts of perception, the very way we see the world?”  (And just for the record, I got turned onto this great collection at Edge by kerim’s post, Rethinking Language and Culture, over at Savage Minds, so please check what kerim has to say!)

 Here’s the opening Boroditsky provides us:

 “I used to think that languages and cultures shape the ways we think. I suspected they shaped the ways we reason and interpret information.  But I didn’t think languages could shape the nuts and bolts of perception, the way we actually see the world.  That part of cognition seemed too low-level, too hard-wired, too constrained by the constants of physics and physiology to be affected by language.”

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