His Brain, Her Brain

Friday, April 29th, 2005

His Brain, Her Brain summarizes much of the research on sexual differences in brain function. I wasn’t familiar with these findings:

But male rats sometimes learn better in the face of stress. Tracey J. Shors of Rutgers University and her collaborators have found that a brief exposure to a series of one-second tail shocks enhanced performance of a learned task and increased the density of dendritic connections to other neurons in male rats yet impaired performance and decreased connection density in female rats. Findings such as these have interesting social implications. The more we discover about how brain mechanisms of learning differ between the sexes, the more we may need to consider how optimal learning environments potentially differ for boys and girls.

Although the hippocampus of the female rat can show a decrement in response to acute stress, it appears to be more resilient than its male counterpart in the face of chronic stress. Cheryl D. Conrad and her co-workers at Arizona State University restrained rats in a mesh cage for six hours — a situation that the rodents find disturbing. The researchers then assessed how vulnerable their hippocampal neurons were to killing by a neurotoxin — a standard measure of the effect of stress on these cells. They noted that chronic restraint rendered the males’ hippocampal cells more susceptible to the toxin but had no effect on the females’ vulnerability. These findings, and others like them, suggest that in terms of brain damage, females may be better equipped to tolerate chronic stress than males are. Still unclear is what protects female hippocampal cells from the damaging effects of chronic stress, but sex hormones very likely play a role.

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