Physical activity, cardiorespiratory fitness and neurophysiological correlates of memory in young adults

Background: Young adulthood represents a critical period of development characterized by significant cognitive, social, and personal demands that require robust cognitive abilities for effective decision-making and goal achievement. While memory is essential for navigating these challenges, much of the existing research has primarily examined cognitive performance in childhood and older adulthood, leaving memory function in young adults less explored. During young adulthood, key brain regions responsible for cognitive processing and memory continue to mature, suggesting a unique window for cognitive interventions. Physical activity and cardiorespiratory fitness are increasingly recognized for their positive impact on memory, with potential benefits across various memory systems. Nonetheless, studies examining the relationship between memory and these factors in young adults remain limited, particularly in terms of understanding the underlying neurophysiological mechanisms. By incorporating neurophysiological markers, researchers can gain deeper insights into how physical activity and cardiorespiratory fitness might influence memory through specific neural pathways.
Aims: The primary aim of this PhD project was to advance the understanding of the associations between physical activity, cardiorespiratory fitness, and neurocognitive memory function in young, healthy adults. Additionally, the project aimed to identify and examine the neurophysiological mechanisms underlying these associations by integrating behavioral and neurophysiological data, including the analysis of selected off-task and on-task electrophysiological markers to elucidate the complex interplay between neurophysiological indices and cognitive memory performance. The following key aims were outlined:
(1) Investigate the association between physical activity and verbal short- and long-term memory, with a particular focus on the potential mediating role of Individual Alpha Peak Frequency (IAPF) as an off-task marker indicative of general cognitive ability.
(2) Investigate the association between cardiorespiratory fitness and working memory, as well as the potential mediating role of heart rate variability (HRV) as an off-task marker indicative of sympathovagal modulation.
(3) Investigate the association between cardiorespiratory fitness and working memory maintenance, along with the potential mediating role of event-related potential (ERP) components, specifically P300 and contingent negative variation (CNV), as on-task markers of attentional allocation and cognitive control.
Methods: This thesis includes the cross-sectional analysis of the longitudinal MEMOCAST project, examining the associations between physical activity, cardiorespiratory fitness, and neurocognitive memory function in young, healthy adults. Conducted at the University of Basel, the study recruited 115 participants aged 18-35, who were assessed through a laboratory-based evaluation, online questionnaires, and ambulatory monitoring. The primary cognitive memory outcomes included visual working memory, assessed by the Sternberg task, and verbal episodic memory, evaluated through the immediate and delayed free recall task. Selected electrophysiological markers were captured using electroencephalography (EEG) and electrocardiography (ECG). Neurophysiological measures included task-related ERP components P300 and CNV, as well as IAPF and HRV at resting-state. Cardiorespiratory fitness was estimated using the Åstrand submaximal test to predict maximal oxygen uptake (V̇O2max). Additionally, ambulatory assessment included a seven-day accelerometer-based recording of physical activity. This multimodal approach allowed for a comprehensive analysis of behavioral and neurophysiological correlates of memory.
Results: Across the overarching aims of this PhD project, the following findings have emerged: higher levels of physical activity and cardiorespiratory fitness were associated with enhanced memory performance, particularly under conditions demanding greater cognitive resources. Specifically, vigorous physical activity was associated both short- and long-term verbal memory in women, while cardiorespiratory fitness was associated with working memory performance under high cognitive load across sexes. Neurophysiological markers provided varied insights, with CNV emerging as a significant on-task marker of proactive cognitive control. Higher cardiorespiratory fitness was linked to increased CNV negativity, reflecting enhanced preparatory processing and proactive cognitive engagement predictive of working memory maintenance. However, off-task markers, including IAPF and HRV, did not mediate the relationship between physical activity or cardiorespiratory fitness and memory performance, suggesting that these markers may not fully capture the underlying mechanisms. Similarly, the P300 component, hypothesized to reflect attentional resource allocation, was not significantly associated with cardiorespiratory fitness or memory performance, suggesting its lesser sensitivity to fitness-related cognitive effects compared to CNV in young adults.
Conclusion: In summary, this thesis underscores the unique and multifaceted contributions of physical activity and cardiorespiratory fitness to memory functions and cognitive control in young adults, with specificity based on memory type and task demands. The results suggest that even in a demographic traditionally considered to be at peak cognitive capability, structured physical activity and high cardiorespiratory fitness may yield measurable cognitive advantages, particularly in highly demanding memory tasks that necessitate sustained proactive cognitive engagement. This thesis supports a personalized approach to cognitive function promotion, indicating that physical activity and cardiorespiratory fitness are significantly associated not only with memory functions but also with proactive cognitive control strategies, potentially predictive of long-term cognitive resilience and mental well-being.