Dynamic exercise improves cognitive function in association with increased prefrontal oxygenation

The Stroop test was performed before and after ergometer exercise for 15 min at 20, 40, and 60 % of maximum voluntary exercise (EXmax), in order to examine whether dynamic exercise is capable of improving cognitive function and whether the changes in regional cerebral blood flow of the prefrontal cortex are associated with the cognitive improvement. Subjects were asked to answer the displayed color of incongruent color words as quickly as possible. The total time period and the number of errors for the Stroop test were measured as an index of cognitive function. The concentrations of oxygenated-hemoglobin (Oxy-Hb) and deoxygenated-hemoglobin (Deoxy-Hb) in the cerebral prefrontal area were measured with near-infrared spectroscopy to determine the changes in regional cerebral blood flow. Ergometer exercise at 40 % of EXmax, but not 20 and 60 % of EXmax, shortened (P < 0.05) the total time period for the Stroop test by 6.6 ± 1.5 % as compared to the time control. In contrast, the number of errors was not altered by exercise at any intensity. The Oxy-Hb in bilateral prefrontal cortices increased during the Stroop test, while the Deoxy-Hb in those areas was unchanged. Ergometer exercise at 40 % of EXmax, but not at 20 and 60 % of EXmax, significantly augmented the response in the prefrontal Oxy-Hb during the Stroop test. The magnitude of the increased prefrontal Oxy-Hb response tended to correlate with the reduction in total time period for the Stroop test. Thus, it is likely that ergometer exercise at moderate intensity for 15 min may improve cognitive function through the increased neural activity in the prefrontal cortex.