The Emergence of Collaborative Brain Function

It doesn’t take a neuroimaging study to see that adolescents are in a state of flux. It is the time in our lives that takes us from having the mind and body of a child to possessing the full mental and physical faculties of a young adult. In terms of cognitive ability it is during this time that a number of very advanced cognitive abilities are slowly coming online. These abilities include risk perception [consequence representation], metacognition [thinking about thinking], counterfactual thinking [alternate possibilities], and abstract reasoning [higher-order relationships]. In short, we are able to represent a much larger amount of information in new and complex ways, relating this information together in ways that are impossible for a 10-year-old brain.

Now, here’s the $10,000 question: what is going on in the brain to accomplish this?

One piece of that puzzle has been investigated by Beatriz Luna and John Sweeney. They conducted a series of experiments investigating the development of response inhibition by using an antisaccade task with adolescents and adults. The antisaccade task is founded on our natural tendency to move our eyes to the appearance of a new object in our visual field. When we are instructed to move our eyes to these new objects it is called a prosaccade – you are reinforcing an already strong natural behavior. When we are instructed to move our eyes away from the new objects it is called an antisaccade – you are having to inhibit the natural response and engage in the opposite behavior. Naturally, this is much more difficult than the prosaccade condition and is considered by many to be a metric for cognitive flexibility (Hutton and Ettinger, 2006).

There are two main conclusions that I have taken away from the Luna and Sweeney papers. These are conclusions so important that they end up getting cited in just about every paper that I write.

1. Just because an adolescent has shown an adult level of performance does not mean that they are arriving there in an adult-like way. As adolescents get older they tend to make fewer and fewer errors during the antisaccade task. This trend continues until roughly the age of 15, when they have nearly reached an adult level of performance (Luna, Garver, Urban, Lazar, and Sweeney, 2004). However, looking at the PET or fMRI data for a 15-year-old during an antisaccade task tells a different story. The adolescents have different levels of activity in the frontal eye fields, intraparietal sulcus, thalamus, cerebellum, and superior colliculus (Luna et al., 2001). So, while the adolescents could complete the antisaccade task looking like an adult, their brain was accomplishing this feat using an immature pattern of regional activity.

2. A large part of the cognitive maturation observed in adolescence comes from the ability for brain regions to increasingly communicate and collaborate. This runs contrary to frontal theories, which theorize that developmental increases in cognitive ability are largely due to the late maturation of prefrontal executive function Instead, Luna and Sweeney argue that we cannot ignore the functional integration of brain regions in our examination of developmental change (Luna and Sweeney, 2004). This idea is supported by recent DTI studies of the brain, which show that behavioral performance is related to inter-region white matter connectivity (Tuch et al., 2005). As an isolated computational unit a single cortical region is rather useless. It is only through the dynamic exchange of information between regions that advanced cognitive abilities can flourish.

The Luna and Sweeney papers are a staple of my research library. While their evidence is very domain-specific (response inhibition), their conclusions speak volumes about how the brain matures during adolescence. Just because an individual might look and sound like a young adult doesn’t mean that they are one, and hen they finally do make it to adulthood it will have required the combined resources of the whole brain working together.

Refs

* Hutton SB, Ettinger U. (2006). The antisaccade task as a research tool in psychopathology: a critical review. Psychophysiology, May;43(3):302-13. Pubmed: 16805870

* Luna B, Thulborn KR, Munoz DP, Merriam EP, Garver KE, Minshew NJ, Keshavan MS, Genovese CR, Eddy WF, Sweeney JA. (2001). Maturation of widely distributed brain function subserves cognitive development. Neuroimage, 13(5):786-793. Pubmed: 11304075

* Luna B, Garver KE, Urban TA, Lazar NA, Sweeney JA. (2004). Maturation of cognitive processes from late childhood to adulthood. Child Development, Sep-Oct;75(5):1357-72. Pubmed: 15369519

* Luna B, Sweeney JA. (2004). The emergence of collaborative brain function: FMRI studies of the development of response inhibition. Annals of the New York Academy of Sciences, Jun;1021:296-309. Pubmed: 15251900

* Tuch DS, Salat DH, Wisco JJ, Zaleta AK, Hevelone ND, Rosas HD. (2005). Choice reaction time performance correlates with diffusion anisotropy in white matter pathways supporting visuospatial attention. Proceedings of the National Academy of Sciences, Aug 23;102(34):12212-7. Pubmed: 16103359

June 25, 2008 • Posted in: CogNeuro, Development

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