Event-related (de-)synchronisation in arm isometric exertions: A wavelet analysis

Neural activity associated with human voluntary motor control has been investigated using various large scale recording and imaging techniques such as Magnetoencephalog-raphy (MEG), electroencephalographic (EEG), and Electrocor-ticography (ECoG). While the EEG activity patterns associated with movement and especially movement execution are relatively known, there are only few studies that address the characteristics of motor rhythms in isometric exertions, and especially in the planning stage. In this paper we report on the results of an experiment where we have recorded EEG from 8 subjects during preparation, planning, and execution of directional arm isometric exertions in horizontal plane, according to instruction-delay visual cues. Continuous Morlet Wavelet Scalograms of the EEG signals in C_z C₃ C₄ electrodes associated with the task, show (de-)synchronisation patterns in planning and execution of the exertions. Phasic synchronisation in 2-7 Hz frequency band and both phasic and tonic desynchronisation in α (μ), β, and γ frequency bands are observed. Minor differences between contralateral, central and ipsilateral rhythmic motor activities during force generation are indicated and discussed. The results can be used to study the involvement of different brain regions during voluntary isometric tasks. The results pave the way for further clinical studies and also for Brain-Computer Interfacing (BCI) and BCI-rehabilitation research.