CAN PROBIOTIC SUPPLEMENTATION AND ACUTE MODERATE INTENSITY AEROBIC EXERCISE IMPROVE EXECUTIVE FUNCTION POSTSTRESS?

Abstract

Executive function (EF) is an umbrella term for neuropsychological processes involved in the ability to maintain and manage goals. Given the wide range of day-to-day behaviours these processes help support, there is great interest in understanding whether and how EFs can be improved. As performance on EF tasks typically reaches its peak during young adulthood, an effective approach to improving EF among this population may be to help individuals maintain task performance at the upper end of their own abilities in contexts where EF is often compromised. One such context is acute psychosocial stress, which can transiently impair performance across various behavioural EF measures. Supplementation with probiotics and acute aerobic exercise have both displayed the potential to improve EF in multiple populations and can modulate the function of the hypothalamic-pituitary-adrenal axis—a neuroendocrine system crucial for the organism’s stress response. Therefore, the purpose of this thesis was to investigate the effect of one probiotic supplement (Lactobacillus helveticus R0052 and Bifidobacterium longum R0175; 3x109 CFU) and acute moderate-intensity aerobic exercise (20 minutes of stationary cycling at 70% peak power output) on a measure of EF (Switching Stroop task) when administered following an acute stress paradigm. In Chapter 2, although supplementation with Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 did not improve Switching Stroop performance following the Maastricht Acute Stress Test in a young adult population, the probiotic group decreased response times on a Feature Search task relative to placebo. This effect remained significant after false discovery rate correction. In Chapter 3, young adults exposed to the Montreal Image Stress Task and acute aerobic exercise displayed greater improvements in Switching Stroop accuracy across the testing session compared to those exposed to the Montreal Image Stress Task or acute aerobic exercise alone. Taken together, probiotic supplementation and acute moderate-intensity aerobic exercise display the potential to improve cognitive task performance among young adults, although not in the hypothesized manner. Future research will be crucial to replicate observed effects and identify the mechanisms underlying them.