Neurobehavioral mechanisms underlying the effects of physical exercise break on episodic memory during prolonged sitting

Background and objective: Episodic memory is the ability that enables individuals to recall and re-experience previous events and usually includes information concerning the spatial and temporal context. This study examined the effects of a physical exercise break during a period of prolonged sitting on episodic memory. Furthermore, we aimed to investigate whether alterations of functional connectivity patterns might contribute to the exercise-induced changes in episodic memory.

Methods: Sixty healthy male college students were randomly assigned (1:1 ratio) to a prolonged-sitting group (PS group) or a physical-exercise-break group (PE group). The face-name paired-associate learning task was used to probe episodic memory. During the task, cortical hemodynamics in the prefrontal cortex were recorded using functional near-infrared spectroscopy (fNIRS). Changes in cortical hemodynamics were used to determine functional connectivity using graph-theoretical network analysis.

Results: There was no between-group difference in neurobehavioral outcomes at the pretest assessment. During the posttest assessment, compared with the PS group, higher nodal efficiency in the anterior prefrontal cortex (orbitofrontal and frontopolar cortices) was observed during the encoding phase (FDR corrected p values = 0.039), and higher nodal efficiency and degree centrality of orbitofrontal cortex were observed in the retrieval phase in the PE group (FDR corrected p values = 0.035). Moreover, the PE group showed closer temporal correlational interactions between the dorsolateral prefrontal cortex and the anterior prefrontal cortex in the left hemisphere during the episodic memory encoding phase (FDR corrected p values = 0.043), when compared to the PS group. Neither significant between-group difference in accuracy nor correlations between neural and behavioral outcomes were observed after the intervention.

Conclusion: Our findings suggest that a physical exercise break during a prolonged sitting period has neither a beneficial nor a detrimental effect on behavioral performance concerning episodic memory. However, physical breaks do facilitate functional connectivity patterns of the prefrontal cortex while performing a episodic memory task.