Electrical activity and reactivity of the rhinencephalic, pararhinencephalic and thalamic structures: Prolonged implantation of electrodes in man

Abstract

The authors present some of the principal considerations based on observations during simultaneous deep cerebral recording in 94 cases of neuro-psychiatric disorders, which could be classified as follows: 32 cases of epilepsy, 56 cases of extrapyramidal syndromes, four cases of schizophrenia and two of severe psychasthenia with associated motor manifestations. The discussion is concerned primarily with the manifestations of temporal lobe epilepsy, but reference is also made to the phenomena encountered in cases of “centrencephalic” epilepsy (grand mal, myoclonic petit mal.) The non-epileptic cases have been included in this investigation only for the purpose of pointing out some substantial differences between their records and those of the epileptic patients. After a brief introduction concerning the phenomena of diffusion, spread and activation, considered on the basis of the data obtained by animal experiments, a number of conclusions are reported, which can be summarized as follows: 1. 1. It appears to have been adequately demonstrated that the hippocampo-amygdalar structures play a predominant part in the precipitation and maintenance of epileptic attacks, in the first place those of temporal, but also those of so-called centrencephalic nature. The activity of either structure, or their synergic activities, may be regarded as the “starter” of the temporal attack; they play a very important role in bringing about certain functional conditions of the neopallium which facilitate the occurrence of generalized attacks of the grand mal type. 2. 2. The relationship between the convulsive electrical activity of the rhinencephalic structures and activity of the same type in the neopallium are rather complicated, but it appears justifiable to state that the attacks of these two structures run a dissociated course. 3. 3. The importance of the rhinencephalic system in bringing about the alterations of so-called centrencephalic epilepsy is definitely confirmed but it has proved rather doubtful whether the thalamus is also concerned in these abnormal manifestations. 4. 4. The observations made during stimulation of the rhinencephalic structures, and the occurrence of after-discharge in these structures, have yielded material that is useful for the interpretation of the electrical aspects of temporal attacks and the clinical phenomena which are associated with these attacks. The data obtained by depth and surface recording in human subjects are briefly considered against the background of the experimental findings in animals, with emphasis on the advantages of investigations carried out directly in epileptic patients.