Fatigue-induced reversed hemispheric plasticity during motor repetitions: A brain electrophysiological study

Abstract

Based on a preliminary case study, we conducted an event related potentials (ERPs) research to explore the relationship between repetitive finger tapping and brain electrophysiological potentials. This present study found that the errors increased with motor repetitions during tapping tasks by right hand especially in the third stage. We defined this stage as the fatigue stage and the first stage as the initial stage. In the fatigue stage, the decreased N1 amplitudes (30-80 ms) with the right fronto-central and right central electrodes (FC4 and C4) were observed, while comparing with the initial stage. Moreover, the pronounced P2 amplitude (150-200 ms) and increased signal with time on right hemisphere (F4 and C4 electrodes) under fatigue state were noticed. Conversely, the contralateral left electrodes (FC3, C3, and F3) did not show aforementioned N1 and P2 differences between two stages. After using the Frequency Extraction method, a clear lateralized pattern in the fatigue stage was found. The left hemisphere showed lower and the right hemisphere showed higher alpha frequency phase content evolution. It was concluded that fatigue did lower the involvement of some areas in the brain but also did make right hemisphere take on more workload during the tapping task with right hand. We call this compensatory change as "fatigue-induced asymmetric hemispheric plasticity". Besides, less signal change between two hemispheres in the fatigue stage was also found. Therefore, the mechanism of transcallosal interaction is strongly related to the fatigue state induced by the motor repetitions. © Springer-Verlag Berlin Heidelberg 2006.