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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Sleep, Eat, Sex – Orexin Has Something to Say

Blogging on Peer-Reviewed ResearchOrexin is a neuropeptide which is released by the posterior lateral hypothalamus, and is linked to wakefulness and sleep, appetite regulation, and the motivation of sexual and addictive behaviors.  One apt way to think about it is as a hormone in the brain, combining some of the popularly conceived effects of adrenaline and testosterone into one. 

(Don’t get too excited now!  I am just trying to give you a way to think about it, that orexin works to promote arousal and response…)

I am writing a post on the links of orexin to appetitive behavior, particularly addiction, but I’ve generated a lot of material.  So I am going to give you this one first, which summarizes aspects of orexin (also known as hypocretin) and neurological function with respect to sleep, appetite and sex. 
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Tools, mirrors and the expandable body

Michael Balter writes in Science NOW Daily News, Tool Use Is Just a Trick of the Mind, about recent research led by Italian neuroscientist, Giacomo Rizzolatti of the University of Parma, head of the team responsible for discovering ‘mirror neurons’ (which I’ve been banging on about for a while, here and here). Rizzolatti’s team was looking at how primate brains managed to do the same tasks with hands and with tools. As Balter describes the research: ‘So how did primates learn to use tools in the first place? A new study in monkeys suggests that the brain’s trick is to treat tools as just another body part.’

Two monkeys were trained from six to eight months to grasp food with pliers. Then the team documented the activity of 113 neurons in areas F5 and F1, a region linked to manipulating objects. How did the monkeys’ motor areas act when using the tools?

The researchers first established the brain’s firing sequence when the monkeys grasped only with their hands. The experiment was then repeated while the monkeys used normal pliers that required first opening the hand and then closing it to grasp the food. The same neurons fired in the same order. Remarkably, the same neurons also fired, in the same order, when the monkeys used “reverse pliers” that required them to close their fingers first and then open them to take the food, the team reports online today in the Proceedings of the National Academy of Sciences.

Balter summarize their conclusions: ‘Rizzolatti and his co-workers conclude that when learning to use a tool, the pattern of neuronal activity is somehow transferred from the hand to the tool, “as if the tool were the hand of the monkey and its tips were the monkey’s fingers.”‘

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Dopamine and Addiction – Part One

By Daniel Lende 

The Pathway 

In your brain you have a system that comes up from some of the oldest evolved parts of your brain to some of the most recently evolved parts.  Reptile parts to ape parts.  In brain research on addiction, it’s generally called the mesolimbic dopamine pathway or system.  All the main addictive drugs affect this system, making the mesolimbic pathway a core component in addictive behavior.  Addictive experiences—gambling, shopping, eating and sex—also impact the mesolimbic dopamine system. 

In both scientific research and the popular press, the dopamine system is often cast in the role of “bad boy,” a hard-wired brain circuit that has gotten out of control, self-indulging in an orgy of pleasure.  That neat story tells us a lot about how we cast our own morals onto the brain, selectively picking out research to provide a nice scientific sheen.  Hard-wired for hedonism, we have to work even harder at self-control.   

It strikes me as the same sort of story that addicts know how to spin so well.  So let’s be blunt.  Denial! 
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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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