Sex differences in hippocampal function

Abstract

Sex differences in the function of the hippocampus have been observed in numerous mammalian species. However, the magnitude, extent, and specificity of these differences are unclear because they can depend on factors including age, methodology, and environment. This Review will discuss seminal studies examining sex differences in hippocampal memory, neuronal morphology, synaptic plasticity, and cell signaling in humans and rodents. We also describe possible organizational and activational effects of sex steroid hormones during early development, puberty, and adulthood that may lead to sex differences observed in the hippocampus. We conclude by discussing the implications of sex differences in hippocampal function for mental health. V C 2016 Wiley Periodicals, Inc.Key words: hippocampus; memory; puberty; adolescence; dendritic spines; plasticity; cell signaling Few scientific topics have garnered as much recent attention in both popular and scientific culture as sex differences. Books from the popular press and media reports about new scientific findings or gender inequalities in the workplace have sparked a national conversation about the extent to which men and women differ and whether these differences matter for education, employment, and opportunity. In the wake of high-profile cases in which men and women exhibited different reactions to drugs prescribed to relieve sleep disturbances, allergy symptoms, and gastrointestinal distress (Rabin, 2013), the National Institutes of Health (NIH) has dramatically altered its guidelines for grant proposals, now requiring investigators to consider "sex as a biological variable" in their applications (Clayton, 2016). This new dictum for scientists is a long-overdue response to the fact that very few biomedical research studies have historically included female subjects, and even fewer have directly compared effects between males and females. As stated by the NIH's Office of Women's Health, the policy is designed to "expand our currently incomplete knowledge base that plays a critical role in informing the development of sex-and gender-appropriate medical care for women and men" (Clayton, 2016). We applaud the effort driving this policy and recognize that a key element necessary for its success is a more widespread dissemination of information to biomedical scientists about sex differences, or lack thereof, in the brain and behavior. As such, special issues such as this one and others (McCarthy, 2016) should greatly aid in providing a scientific foundation for investigators new to sex-differences research.Sex differences in cognitive function among humans and nonhuman animals have been reported in earnest for well over 2 decades (Williams et al

Intact memory for local and distal cues in male and female rats that lack adult neurogenesis

“…Since rearing is typically interpreted as a behavior that promotes investigation of the distal environment, this suggests that males may be more likely to re-explore the distal environment when there are changes to local cues. Considered another way, this finding may be consistent with evidence that women tend to have better object-related memory than men and, while rodent data are equivocal, it might also fit with reports of sex differences in object-location memory (reviewed in (Koss and Frick, 2017)).…”

Long-term HIV-1 Tat Expression in the Brain Led to Neurobehavioral, Pathological, and Epigenetic Changes Reminiscent of Accelerated Aging

“…1, Table 1 and 2). Across species studies show that males perform better in spatial memory test than females in human [75] and that the sex difference in spatial memory is more pronounced in older mice [76], which implicates that males' spatial memory is more sensitively suffered by HIV-1 Tat. Moreover, agingassociated menopause, accompanied by estrogen decline may be related to the worse memory in all females [77,78], which may further fade the impact of HIV-1 tat on female mice.…”

Sex‐specific contribution of DHEA‐cortisol ratio to prefrontal‐hippocampal structural development, cognitive abilities and personality traits

“…In particular, hippocampal volumes increase linearly in late childhood in both sexes but then follow different trajectories in males and females later during adolescence such that the linear increase continues for males, whereas there may be no change or a slight decrease in hippocampal volumes in females . Dendritic pruning has also been described in the medial prefrontal cortex (Figure ) of female but not male rats, suggesting sex‐specific dendritic pruning in cortical regions as well . Surprisingly, it remains unclear to what extent sex differences in the hippocampus are affected by pubertal steroid hormones.…”