Ng, Siew Cheok (2003) Changes in the electroencephalogram MU rhythm during hand movements / Ng Siew Cheok. Masters thesis, University of Malaya.
Abstract
The electroencephalogram (EEG) mu rhythm for four types of actual and imagined hand movements (grabbing, key pinch, tip to tip pinch and tripod pinch) were studied for the cases of the eyes opened and closed. The EEG signals were obtained from 16 healthy subjects using a 40 channels Medelec Profile EEG data acquisition equipment. Their ages were between 19 and 28. For the present study, the results from the C3 electrode that was placed at the contralateral motor cortex region that corresponds with the right hand movement are of. particular interest. The EEG signals at the frequencies that correspond to the mu rhythm were analysed using the Fourier Analysis and Event Related Desynchronisation (ERD) methods. From the Fourier Analysis study, the attenuation of the mu rhythm for actual hand movement was found to be of a longer duration than those of the corresponding imagined hand movement. The durations of the attenuation of the mu rhythm for actual hand movement for tripod pinch (complex movement) and grabbing movement (more muscles involved) were longer than those for the key pinch and tip to tip pinch (simple movements which involved fewer muscles). A similar trend was also observed for the imagined hand movements. The results obtained from the ERD method are similar to those obtained using the Fourier Analysis method. The ERD method has the advantage of requiring less computational time and it is not constrained by the Uncertainty Principle as in the case ofthe Fourier Analysis method. Coherence Analysis was used to correlate the EEG signals obtained from two different locations of the scalp. The coherence of the mu rhythm for two electrodes placed at the contralateral hemisphere during actual hand movement was found to be almost zero (<0.05), while those for the imagined hand movement showed a reduction of coherence to the level of 0.2. The coherence of the mu rhythm for two electrodes placed at the ipsilateral hemisphere showed a reduction to the level of0.55 during actual hand movement, while the coherence of the mu rhythm for the imagined hand movement was similar to those of the resting state (0.85).
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