Thalamic control of spontaneous alpha-rhythm and evoked responses

EEG, depth recordings from the thalamus, visual-evoked potentials, and readiness motor potentials were analyzed with a computer in 40 patients with involuntary movements and intractable pain who underwent stereotactic thalamotomy. It was demonstrated that there were significant correlations in alpha-rhythms between the ventrolateral (VL) nucleus and the frontocentral cortex, and also between the centromedian nucleus and the centroparietal cortex, with the phase difference of the cortex lagging behind the thalamus. Relationships between the thalamic VL nucleus and the frontocentral cortex were significant not only in alpha-rhythms, but also in evoked responses following photic stimulations, voluntary movements, and electrical thalamic stimulation. Thalamotomy produced a bilaterally decreased synchronization of the cortical alpha-rhythms, which recovered within 6 months.