Acute effects of cocoa flavanols on visual working memory: maintenance and updating

Abstract

Background: Consumption of cocoa flavanols may have acute physiological effects on the brain due to their ability to activate nitric oxide synthesis. Nitric oxide mediates vasodilation, which increases cerebral blood flow, and can also act as a neurotransmitter. Objectives: This study aimed to examine whether cocoa flavanols have an acute influence on visual working memory (WM). Methods: Two separate randomised, double-blind, placebo-controlled, counterbalanced crossover experiments were conducted on normal healthy young adult volunteers (NExp1 = 48 and NExp2 = 32, gender-balanced). In these experiments, 415 mg of cocoa flavanols were administered to test their acute effects on visual working memory. In the first experiment, memory recall precision was measured in a task that required only passive maintenance of grating orientations in WM. In the second experiment, recall was measured after active updating (mental rotation) of WM contents. Habitual daily flavanols intake, body mass index, and gender were also considered in the analysis. Results: The results suggested that neither passive maintenance in visual WM nor active updating of WM were acutely enhanced by consumption of cocoa flavanols. Exploratory analyses with covariates (body mass index and daily flavanols intake), and the between-subjects factor of gender also showed no evidence for effects of cocoa flavanols, neither in terms of reaction time, nor accuracy. Conclusions: Overall, cocoa flavanols did not improve visual working memory recall performance during maintenance, nor did it improve recall accuracy after memory updating.