Age, adrenal steroids, and cognitive functioning in captive chimpanzees (Pan troglodytes)

Abstract

BackgroundDehydroepiandrosterone-sulfate is the most abundant circulating androgen in humans and other catarrhines. It is involved in several biological functions, such as testosterone production, glucocorticoid antagonist actions, neurogenesis and neuroplasticty. Although the role of dehydroepiandrosterone-sulfate (DHEAS) in cognition remains elusive, the DHEAS/cortisol ratio has been positively associated with a slower cognitive age-decline and improved mood in humans. Whether this relationship is found in nonhuman primates remains unknown.MethodsWe measured DHEAS and cortisol levels in serum of 107 adult chimpanzees to investigate the relationship between DHEAS levels and age. A subset of 21 chimpanzees was used to test the potential associations between DHEAS, cortisol, and DHEAS/cortisol ratio in cognitive function, taking into account age, sex, and their interactions. We tested for cognitive function using the primate cognitive test battery (PCTB) and principal component analyses to categorize cognition into three components:spatial relationshiptasks,tool use and social communicationtasks, andauditory-visual sensory perceptiontasks.ResultsDHEAS levels, but not the DHEAS/cortisol ratio, declined with age in chimpanzees. Our analyses forspatial relationshipstasks revealed a significant, positive correlation with the DHEAS/cortisol ratio.Tool use and social communicationhad a negative relationship with age. Our data show that the DHEAS/cortisol ratio, but not DHEAS individually, is a promising predictor of spatial cognition in chimpanzees.