Activation processes during mental practice in stroke patients

In healthy subjects, mental practice is known to improve motor performance. It is also known to be accompanied by a higher central nervous activity. Since such effects seem to be desirable for rehabilitation, we investigated the possibility of detecting changes in central nervous activity by means of EEG in stroke patients, and whether these changes were similar to those observed in healthy subjects. 12 left-sided hemiplegic patients who underwent a specific post-stroke rehabilitation treatment were requested to perform a simple arm movement sequence. In the following mental practice period the patients were requested to image the same sequence without any real movement. EEG background activity was recorded during rest and imagination periods. After the calculation of z-transformed power values within the theta, alpha, and beta-1 band, differences between rest and imagination periods were evaluated for their significance. Stroke patients show significant decreases of theta, alpha, as well as beta-1 power during mental practice in comparison to the rest period. These changes are similar to those obtained in healthy subjects. Theta power decreases in central and parietal leads. Central alpha power diminishes only during imagination of the contralateral arm. This phenomenon as well as the decrease of beta-1 power in central derivation were also obtained during real motor performance and might indicate an activation of the sensorimotor cortex. In accordance with the hypothesis of internal feedback mechanisms, this activation is a necessary prerequisite for motor learning during mental practice.