Elevated Cortisol Leaves Working Memory Unaffected in Both Men and Women

Abstract

Activation of the hypothalamic-pituitary-adrenal (HPA) axis (as might occur, for example, when the organism encounters a threat to allostatic balance) leads to the release of cortisol into the bloodstream and, ultimately, to altered neural functioning in particular brain regions (e.g., the prefrontal cortex (PFC)). Although previous studies suggest that exposure to acute psychosocial stress (and hence, presumably, elevation of circulating cortisol levels) enhances male performance on PFC-based working memory (WM) tasks, few studies have adequately investigated female performance on WM tasks under conditions of elevated cortisol. Hence, we compared associations between elevated (relative to baseline) levels of circulating cortisol and n-back performance in a South African sample (38 women in the late luteal phase of their menstrual cycle, 38 men). On Day 1, participants completed practice n-back tasks. On Day 2, some completed the Trier Social Stress Test (TSST), whereas others experienced a relaxation period, before completing 1-back and 3-back tasks. We measured self-reported anxiety and salivary cortisol at baseline, post-manipulation and end of session. We reconstituted group assignment so that all women with elevated cortisol were in one group (EC-Women; n = 17), all men with elevated cortisol were in another (EC-Men; n = 19), all women without elevated cortisol were in a third (NoEC-Women; n = 21), and all men without elevated cortisol were in a fourth (NoEC-Men; n = 19) group. Analyses suggested this reconstitution was effective: in EC, but not NoEC, groups cortisol levels rose significantly from baseline to post-manipulation. Analyses of n-back data detected significant relations to task load (i.e., better performance on 1-back than on 3-back tasks), but no significant relations to sex, performance accuracy/speed, or cortisol variation. The data patterns are inconsistent with reports describing sex differences in effects of stress on WM performance. We speculate that cross-study methodological differences account for these inconsistencies, and, particularly, that between-study variation in the magnitude of baseline cortisol levels might affect outcomes. For instance, diurnal cortisol rhythms of South African samples might have flatter curves, and lower baseline values, than predominantly Caucasian samples from the United States and western Europe due to greater prenatal and lifetime stress, more socioeconomic disadvantage and faster ancestral life history (LH) strategies. We describe ways to disconfirm this hypothesis, and urge further cross-national research exploring these possibilities.

Physical Activity versus Psychological Stress: Effects on Salivary Cortisol and Working Memory Performance

“…Our null findings regarding the relationship between changes in cortisol and working memory capacity align with recent empirical work among humans [30]. These null findings have occurred in samples of men [31,32,33] and women [34,35].…”

Isometric handgrip exercise speeds working memory responses in younger and older adults.

“…We selected a moderate-to-large size estimate for the effects of handgrip on n -back performance, tonic pupil diameter, and phasic pupillary responses. This estimate was based on a previous report of medium-to-large effects of handgrip on task performance and pupil dynamics (Mather et al, 2020), as well as reports of medium-to-large effects of both stress and threat of shock on working memory performance (Bolton & Robinson, 2017; Human et al, 2018; Schoofs et al, 2013). To account for possible exclusions, we therefore aimed for a sample size of 56 younger and 56 older participants.…”

“…Therefore, changes in arousal may be particularly relevant for tasks that engage frontoparietal brain regions, including working memory, the short-term storage and maintenance of information in memory (Baddeley, 2003). Previous studies have indicated that stress can either impair, enhance, or not affect working memory (Duncko et al, 2009;Human et al, 2018;Schoofs et al, 2008Schoofs et al, , 2013, but it is unclear how non-stress-related increases in arousal, such as those induced through isometric handgrip, affect working memory.…”