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HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY I 



complex. The rhythmical variations are in every way 

 comparable to postdischarges provoked by an electric 

 current : that is to say, they appear as rhythmical dis- 

 charges of localized spikes whose frequency diminishes 

 progressively and which are often interrupted by slow 

 waves or intervals of silence before they come to an 

 end. 



Recording with microelectrodes, Thomas et al. 

 (i88) observed in addition cellular discharges which 

 were rather different from those provoked by strych- 

 nine or a single electric shock. The units often showed 

 spontaneous prolonged bursts of activity, usually be- 

 ginning with a high frequency train of impulses (ap- 

 proximately I, coo cps) followed by longer bursts at 

 somewhat lower frequencies (approximately 300 cps). 

 Such a discharge may repeat its whole cycle inter- 

 mittently or settle down to a steady train of impulses 

 at about 150 to 200 cps which may be kept up in- 

 definitely. 



(T) Propagation 0/ experimental isocortieal epileptie dis- 

 charges. The use of recording electrodes at a distance 

 from the stimulated region has shown that all epilep- 

 tic discharges are propagated locally and to a greater 

 or lesser distance. Local propagation proceeds very 

 slowly (from i mm per sec. to i mm per min.) through 

 a multitude of fine fibers and synapses, often arranged 

 in reverberating circuits which constitute the fibrillary 

 network of the cortex. Studying local propagation by 

 means of vector recordings. Green & Naquet (93) 

 came to the conclusion that it may represent extra- 

 synaptic spread from cell to cell following dendritic 

 depolarization. Sporadic and rhythmical discharges 

 are propagated at a distance in different manners 

 (160). The rhythmical discharges (the 'postdis- 

 charges') are propagated much more widely than 

 are the sporadic discharges; it is the former type only 

 that we shall be considering here, for it alone cor- 

 responds to the propagation of an epileptic seizure. 

 (The sporadic discharges only represent the ' inter- 

 seizure' irritative manifestations, and a knowledge of 

 them is not indispensible for understanding the actual 

 seizures.) Numerous authors have studied the propa- 

 gation of postdischarges from different parts of the 

 cerebral cortex. A complete bibliography of the 

 numerous works devoted to these cortical postdis- 

 charges can be found in Green & Naquet (93). We 

 shall give only a brief account' of subcortical propa- 



gation of postdischarges engendered in different parts 

 of the cerebral cortex, neglecting corticocortical 

 propagation which takes place mainly in the homolo- 

 gous contralateral region by means of commissural 

 fibers.'" 



Frontal postdischarges are propagated chiefly to 

 the brain stem reticular formation (tegmentum 

 mesencephali, hypothalamus and intralaminar nuclei 

 of the thalamus) and secondarily to the caudate 

 nucleus, the amygdala and the hippocampus. Cingu- 

 lar postdischarges have a similar but less marked 

 propagation, and orbital postdischarges propagate 

 particularly to the amygdala and hippocampus. 



Postdischarges in the motor region travel chiefly to 

 the brain stem reticular formation, the septal region 

 and the corpus striatum. Temporal postdi.scharges 

 are mainly propagated to the amygdala, hippo- 

 campus, septal region, subthalamus, hypothalamus 

 and the mesencephalic reticularis, and secondarily 

 to the corpus striatum and the pulvinar. Occipital 

 postdischarges go chiefly to the thalamus (pulvinar 

 and lateral geniculate body, and neighboring intra- 

 laminar nuclei) and secondarily to the subthalamus 

 and the reticular formation. 



Thus the postdischarges localized in the cortex are 

 characterized by remarkably important subcortical 

 propagation which nearly always involves the brain 

 stem reticular formation and the amygdalohippo- 

 campal system. This tendency for cortical epileptic 

 discharges to invade subcortical nonspecific structures 

 or the brain stem had already been evidenced by the 

 interseizure sporadic discharges. Thus von Baum- 

 garten et al. (190) demonstrated the reticular influ- 

 ence of strychnine spikes and potentials evoked by a 

 single shock in the rolandic region; this was mani- 

 fested by reinforcement, or conversely by inhibition 

 of the spontaneous discharges of single reticular units 

 recorded with microelectrodes. 



EXPERIMENT.^L P.'^RTI.AL EPILEPSY OF RHINENCEPH.^LIC 



(allocortical) ORIGIN. We shall study seizures 

 caused by epileptogenic measures involving not only 

 the allocortex but all the rhinencephalon, both its 

 cortical and nuclear parts. 



a) Implantation of in-dwelling electrodes. This method 

 has permitted the study of seizures of partial epilepsy 

 provoked by electrical stimulation of the rhinen- 



' This summary takes account of the works of Walker & 

 Johnson (192), Kaada (119), Ajmone-Marsan & StoU (6), 

 StoU et al. (186), Gastaut et al. (72), Jasper el al. (108), Segundo 

 et al. (175), French el al. (50), Poggio el al. (158), and Creutz- 

 feld(3i). 



'•" Contralateral homologous conduction takes place via the 

 corpus callosuni or the anterior commissure according to the 

 site of the lesion. This was demonstrated by physiological 

 neuronography (140) and by study of experimental epilepto- 

 genic scars (127-129). 



