Racism-related chronic stress effects on hippocampal-dependent memory
Espinal Martinez, Alan Osvaldo
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The incidence of Alzheimer’s Disease (AD) in the African American (AA) and Hispanic or Latino American populations in the United States (US) is twice as high compared to non-Hispanic White Americans. The study of race-related factors to explain the disparity in the incidence of AD and other health outcomes has been of growing interest. African Americans in the US experience higher discrimination due to race on a daily basis than any other minority group, and race-based discrimination (racism) is a known chronic stressor. It has been shown that in humans and rodents, chronic stress negatively affects hippocampal-dependent memory and reduces hippocampal volume. Pattern separation (PS), the ability to create distinguishable memory traces for similar information and thus avoiding interference to discriminate between similarly patterned visual percepts, is known to rely on the dentate gyrus (DG) hippocampal subfield integrity. Although the detrimental effects of chronic stress have been documented before, the effects of racism-related chronic stress (RRCS) on hippocampal-dependent memory system remain understudied. This pilot/preliminary study tested the hypothesis that higher frequency of experiences of discrimination in AA older adults would correlate with deficits in a behavioral PS task and with DG/CA3 volume. Seven African American older residents from the greater Boston area participated in both the cognitive testing to examine behavioral PS and structural MRI to examine DG/CA3 volume. Contrary to our hypothesis, a Spearman correlation analysis did not demonstrate a significant association between discrimination scores and behavioral PS performance or DG/CA3 volume. However, a significant correlation was found between performance on the behavioral PS task and right DG/CA3 volume. These results are consistent with previous studies on PS. Continued future research on the impact of RRCS on the hippocampal memory system among AA older adults as an important modulating factor in health for this population is needed.