Stress coping stimulates hippocampal neurogenesis in adult monkeys

Biology

In "Stress coping stimulates hippocampal neurogenesis in adult monkeys," the authors examine the effects of coping with stress vs. just the experience of stress. Experiencing stress is known to prevent new cell growth in the brain, the hippocampus in particular. Until this research, no studies have shown what neurogenesis (new cell growth) take place in the brain as a result of effective coping with stress. Studies do show that psychotherapy in humans designed to improve coping mechanisms does have a positive effect on the brain. Even when innate methods of coping, not those taught from psychotherapeutic interventions, aid in stress relief. This is especially true for certain types of stress such as social demands. However, this research fills a gap in the literature by showing that coping with stress might actually stimulate neurogenesis. This research was performed on a group of non-human primates because the study of primate brains enables generalization to the human brain. The main research hypothesis is that coping mechanisms stimulates neurogenesis.

To investigate the hypothesis, the researchers used a population of twelve male squirrel monkeys. The monkeys were randomly assigned to different experimental conditions including being housed continually with a familiar male companion; being housed alone for three weeks; and finally, being housed for nine weeks with an unfamiliar male companion. Over 18 months, the researchers alternated the pairings. The researchers measured learning and coping via measuring plasma levels of cortisol that are released during the initial stressor and then afterwards: a basic measure of hormonal output. The researchers also measured neurogenesis (the dependent variable) as well as changes in gene expression. Measures of learning performance on a series of specially-designed tests was also used to measure the dependent variable. In other words, performance on the learning tests is associated with neurogenesis. The gene expression measures were taken to aide future research.

The results showed that performance on the learning tests did change, and the hypothesis was proven. Stress from the change, the intermittent pairings, did increase hippocampal neurogenesis in the adult male squirrel monkeys. Learning, especially spatial learning, was enhanced. Moreover, the corresponding gene expressions changed accordingly.

The authors suggest that the results may be generalized to a human population. With special attention paid to human beings suffering from depression, the authors suggest that specially-designed psychotherapeutic interventions for coping with stress will help stimulate hippocampal neurogenesis. Hippocampal neurogenesis is in turn associated with improved cognition. Therefore, effective coping mechanisms are likely to have a positive impact on overall psychological functioning.