par Bremer, Frédéric 
Référence Electroencephalography and clinical neurophysiology, 1, 1-4, page (177-193)
Publication Publié, 1949
Référence Electroencephalography and clinical neurophysiology, 1, 1-4, page (177-193)
Publication Publié, 1949
Article révisé par les pairs
| Résumé : | Hypotheses concerning the origin and nature of cerebral waves and the general significance of the electroencephalogram were discussed. Reasons are presented which oppose the theory explaining cortical potentials, alpha waves in particular, by the periodic conduction in the cortex of trains of impulses travelling in reverberating circuits. Experimental arguments were presented in favor of the conception identifying cerebral waves with synchronized cellular pulsations, the fundamental autorythmicity manifested by neuronal aggregates of gray matter (analysis of the effects of bulbar and mesencephalic transection and section of the internal capsule; cortical responses to sensory stimulation; the effect of exciting and depressing agents), In order for this rhythmicity of the cortex to be clearly shown and maintained, there is a dynamogenic influence arising from thalamic nuclei, in which the activity is itself sustained by all the "sensitivo-sensoriels" impulses, and also by impulses of cortical origin. Cortico-diencephalic interaction is reenforced by the eventual in-phase relations of thalamic and cortical pulsations when their respective frequencies are close together. There is no necessity of separating two types of cortical activity, spontaneous and provoked, considered to be fundamentally distinct by their neuronal mechanisms. The differences observed between the oscillographic aspects of the projection and association areas can be explained by frequent disturbances in the activity of the projection areas due to aperiodic vollies of corticocipetal impulses arising from sensory receptors. Cortical waves are probably constituted by the superposition of rhythmic and synchronized fluctuations in neuronal membrane potentials with discharges of axonal impulses, of which these fluctuations in membrane potential, acting as an oscillating catelectrotonus, would be the immediate cause. The functional significance of the continuous electrical activity of the cerebral cortex is indicated by the habitual association of a discharge of impulses with each pulsation, a discharge which elicits, depending upon the case, a subliminal excitatory effect (which can eventually become supraliminal), or even an inhibitory action, upon the neuronal aggregates in functional relation with the emitting cortical area. © 1949. |
