Effects of Acute Aerobic Exercise and Task Repetition on the Neural Correlates of Executive Function in Young and Older Adults: A Crossover fMRI Study

BACKGROUND: Acute aerobic exercise may alter neural recruitment supporting executive function; however, age-related differences and task repetition effects remain unclear. PURPOSE: To investigate the effects of acute aerobic exercise and task repetition on brain activity during task switching in young and older adults. STUDY TYPE: Prospective randomized crossover study. POPULATION: Seventeen young and nineteen older healthy adults (18 females). FIELD STRENGTH/SEQUENCE: 3.0 T, BOLD fMRI. ASSESSMENT: fMRI was conducted during a task-switching paradigm before and at 15 and 45 min following 30 min of moderate-intensity walking or sitting on separate days. Neural and behavioral switch costs were computed as differences in BOLD activation, reaction time, and error rates between switch and nonswitch trials. STATISTICAL TESTS: Linear mixed-effects model examined BOLD signals and behavioral performance. Repeated measures correlation examined within-subject associations. p < 0.05 was considered statistically significant. RESULTS: Older adults exhibited significantly greater task-related BOLD activation in the bilateral superior frontal and middle temporal gyri, right angular gyrus, and left precuneus than young adults, despite slightly lower performance (p ≤ 0.002). Task repetition significantly reduced activation in the left middle occipital and middle frontal gyri and right cerebellar cortex in both groups, whereas reaction time significantly improved only in older adults. Following walking, activation in the right dorsolateral prefrontal cortex remained stable in older adults but significantly decreased in young adults, without corresponding behavioral changes (p ≥ 0.365). Regardless of age, activation in the right postcentral gyrus and bilateral superior parietal lobules remained stable after walking but significantly decreased after sitting. Reduced activation with task repetition was significantly associated with faster reaction time, particularly in older adults. DATA CONCLUSION: Acute aerobic exercise may preserve regional brain activation without measurable behavioral benefits, whereas task repetition reduces brain activation across age groups, suggesting modest neural effects of acute aerobic exercise on executive function. TECHNICAL EFFICACY STAGE: 2.