Chapter 29 Event-related desynchronization of the mu rhythm in extension and flexion finger movements

Abstract

Event-related desynchronization (ERD) is the Rolandic mu rhythm that accompanies voluntary movements of the hand or finger by amplitude attenuation. The mu ERD differentiates between left and right finger movements, brisk and slow movements, and force of movement. This chapter analyzes movement-related changes of the mu rhythm over the contralateral sensorimotor hand area (M1) l ipsilateral hand area (S1) in brisk self-paced movements. A dense array of closely spaced electrodes and simple finger movements were used in this analysis. Results showed no significant difference between extension–flexion and flexion–extension sequences in the duration of the first two movements. The frequencies of the movement-reactive component showing maximal desynchronization in the 8–13 Hz band were identical for extension–flexion and flexion–extension movements. Visual analysis of individual power-time series revealed that the mu ERD for flexion-extension movements was greater in eight out of 11 subjects, equal to in one subject, and less in two subjects, as compared to the mu ERD occurring during extension–flexion movement. The topography of the maximal mu ERD differed in extension–flexion and flexion–extension movements. The population of M1 neurones, in contrast to a single M1 neurone, encodes the direction of the finger movement in a three dimensional space. The mu ERD reflects activation of millions of neurones of both Ml and S1 cortex.