Effects of pedaling exercise on human EEG and cerebral oxygenation: Role of brain serotonergic system

Abstract

We previously examined the effect of pedaling exercise (PE) on urinary serotonin (5-HT) level. Since we found the increase in the urinary 5-HT level after PE, we hypothesized that the activity of the 5-HT neuron located in the brain stem may increase during PE. In the present study, we investigated the effects of PE on EEG and cerebral oxygenation in prefrontal cortex (PFC) before, during and after PE. Subjects performed PE for 15 minutes. PE rate and work load were kept at 60 rpm and 90 watt. We used Fast Fourier Transform to obtain the EEG (Cz, Pz) power. Cerebral oxygenation in PFC was assessed by concentration changes in oxygenated hemoglobin (oxyHb) using multi channel near-infrared spectroscopy (NIRS). Urinary and blood 5-HT levels were measured before and after PE. As a result, we found that the spectral power of alpha band (8-13Hz) began to increase at about 7 minutes after the onset of PE. The initial decrease and subsequent increase in oxyHb level in PFC were obtained during PE. OxyHb level in PFC began to increase at about 5 minutes after the onset of PE, and reached a peak at about 13 minutes after the onset of PE. The peak level of oxyHb was higher in more ventral portion of PFC, as compared with dorsal PFC. Since the urinary and blood 5-HT levels increased after PE, we suggest that augmentation of brain 5-HT system is involved in activation of PFC and rise in alpha power of EEG during PE. [J Physiol Sci. 2007;57 Suppl:S162]