Monday, October 5, 2015

Gregarious chimps have more grey matter in specific region of the brain

Chimpanzees with offspring, Photo credit: flickr user Valerie
As one of our closest living relatives, studying the behavior, ecology, and anatomy of chimps provides a look back in time as to what the last common ancestor of chimpanzees and humans may have been like. A recent study examined the brain structure of over one hundred chimpanzees to understand how personality and the brain are connected.

Latzman and colleagues (2015) studied 107 captive chimpanzees by using MRIs and an assessment composed of 41 questions about each individual chimp's personality that was conducted by staff members who care for the animals. The article did not state how long these staff members worked with the chimpanzees, only that they felt they could assess their personalities.

Latzman and colleagues (2015) showed that the volume of gray matter and asymmetry of various regions of the frontal cortex are correlated. Grey matter, found mainly on the outside of the brain, is composed on neuronal cells and unmyelinated axons. (To learn more about grey matter, click here.) Chimpanzees ranked as more dominant, open, and extraverted have greater average grey matter in the frontal cortex of their brains. Extraversion in this article is defined as "energetic approach orientated." Their research also shows that frontal cortex asymmetry, or lack of equality/symmetry, is associated (but not correlated) with dominance, extraversion, and unpredictability.
Source: Biological Psychology 6e via Wikipedia

There are limitations to this study, as Latzman and colleagues (2015) mention. It is impossible to determine the causal relationship. Do personality differences create these structural differences in the brain? Or do structural differences in the brain create these personalities differences? As of right now, we can't answer this question. Interpretations of these findings are also limited by our own understanding of the brain, and we have much to still learn about the structure and function of this complex organ.

Yet, because of this study we have a greater understanding of the biological bases of behavior and personality.  Latzman and colleagues (2015) are the first to study the frontal cortex of the brain and personality in chimpanzees. As we know, chimpanzees are an excellent model for human behavior and personality because they are so closely related to humans. Studies such as this one allow us to refine our understanding of the evolution of our own species.

Food for thought: Would we expect to see the same results in bonobos? Orangutans? Lemurs?

Links of interest:
Cooking chimpanzees
Female friendship in chimpanzees
Differences in tool use between males and females

Works cited:

Robert D. Latzman, Lisa K. Hecht, Hani D. Freeman, Steven J. Schapiro, William D. Hopkins. Neuroanatomical correlates of personality in chimpanzees (Pan troglodytes): Associations between personality and frontal cortex. NeuroImage, 2015; 123: 63 DOI: 10.1016/j.neuroimage.2015.08.041

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