COMPARATIVE STUDY OF THE THALAMIC, CEREBRAL AND CEREBELLAR POTENTIALS

Abstract

The oscillations recorded in the electrocorticograms (ECG) are not specific for the cerebral cortex; the electrothalamogram (EThG) shows slow and rapid waves quite similar to them. The electrocerebellogram (ECG) may show rapid waves only or also slow waves. (Experiments on cats.) The slow waves of the EThG may persist after elimination of corticofugal impulses or after transverse section of the midbrain; the amplitude and frequency of these waves, however, usually are diminished after these operations. With bipolar leads, increase of the distance of the electrodes increases the amplitude of the slow waves of the EThG. The depressive action of ether is not limited to the cortex; it is also noticeable in the EThG; the typical form of the electrothalamogram is preserved in sleep, as induced by dial; also in bulbocapnine catalepsy, both types of waves are retained. Injection of strychnine in curarized animals increases the oscillations of the EThG. Sensory stimulation may induce slow deflections of the string, increase of the brief oscillations, and diminution of the slow waves of the EThG. The electro-corticogram picked up from a circumscribed cortical area (e.g., sigmoid gyri) still shows slow waves after severance of the thalamocortical pathways and of nearly all connections with the rest of the cortex. The oscillations of the electrocerebellogram persist after transverse section of the mid-brain ; they are diminished but still present after severance of the afferent cerebellar tracts. Summation of rapid waves due to successive stimulation of cells in neurone chains may at least partly explain the genesis of the slow waves. The effects of sensory stimulation are explainable on the one hand by appearance of action potentials of the cells reached by the centripetal impulse, on the other hand by the interference between the sensory impulse and the wave circulating in the resting neuron chain.