腦磁活動與自發運動反應時間差異之關係

Abstract

Intra-individual variability in behaviors can be an important indicator of central nervous system integrity. This study aims at understanding the origins of the behavioral reaction time (RT) variability across trials using magnetoencephalography (MEG) in a two-choice reaction time visuomotor task. We classify trials into the fast-response (FR) and the slow-response (SR) groups according to the RTs and we study the oscillatory activity and evoked responses. We found that the pre-stimulus alpha band (8-14 Hz) oscillatory power (0.4 s before the visual stimulus onset) around right posterior sensors was significantly higher in the SR group than in the FR group (p<0.001). The visual and motor evoked responses have significantly smaller amplitude in the SR group than in the FR group. With respect to the onset of the visual stimulus, the peak timing difference between FR and SR groups was only 0~8 ms in the visual cortex and 85 ms in the motor cortex. These results suggest that the posterior alpha power may modulate the brain activity in visual and motor cortices to cause inter-trial RT variability. Such a modulation can be observed after 150 ms from the visual stimulus onset by MEG.