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Le risposte corticali evocate da stimoli somatici, sia periferici che centrali, aumentano di ampiezza durante il sonno profondo. Tale amplificazione e dovuta, almeno in parte, ad una facilitata trasmissione degli impulsi ascendenti a livello del nucleo ventro-postero-laterale del talamo.

This study is based upon 25 selected comatose subjects investigated from the clinical, EEG, and anatomical standpoint. 1. 1. For practical purpose the different degrees of coma were subdivided using as parameters signs and symptoms commonly found in comatose patients, as follows: 1. (a) impairment of consciousness (C 1): 2 cases; 2. (b) moderate coma (C 2): 14 cases; 3. (c) deep coma (C 3): 9 cases. 1. 2. The type of EEG activity found was grouped under the following three headings: 1. (a) generalized EEG changes: 15 cases; 2. (b) unilateral EEG changes: 7 cases; 3. (c) focal EEG changes: 3 cases. 1. 3. The site of cerebral lesion was reconstructed on the basis of macro and microscopic sections. Electroclinical results show that a generalized slow organized activity is not necessarily the bioelectric expression of the majority of comatose patients. No definite relationships are found between degree of coma and type of electroencephalographic changes. Moreover the possibility of eliciting a bioelectric response to stimuli does not appear to be related to the depth of coma. Some interpretational problems posed by the EEG findings are discussed.

Both peripherally and centrally evoked somatic responses vary greatly in amplitude according to the level of vigilance. This effect is due both to modifications of afferent transmission along the somatic pathways and to variations in responsiveness of the cortical neurones. In particular: 1. (a) the afferent transmission at the level of the 1st station (gracilis and cuneatus nuclei) does not seem to be affected by the depth of sleep, being unchanged during deep sleep as compared to light sleep; during arousal it may vary greatly according to concomitant behavioural changes; 2. (b) the afferent transmission at the level of the 2nd station (nucleus ventro-postero-lateralis of the thalamus) is constantly affected by the depth of sleep, being maximal during deep sleep; during arousal it can appear either facilitated or depressed according to the depth of the preceding spell of sleep; 3. (c) somatic cortical responsiveness is maximal during light sleep, being apparently depressed during deep sleep and arousal.

Data derived from the literature and from personal contributions concerning the EEG during coma are summarized as follows

Lo studio delle risposte evocate nelle radiazioni acustiche e nelle arec acustiche primarie da stimolazione delle vie uditive centrali dimostra che: (a) la trasmissione degli impulsi ascendenti a livello del corpo genicolato mediale e facilitata sia durante il sonno profondo che al risveglio mentre, (b) l'eccitabilita corticale e maggiore durante il sonno leggero.

It is clear that during deep sleep the response evoked in the somatosensory cortex of the cat by shocks to the cutaneous nerve or medial lemniscus is not only higher2 but has a shorter latency as well. Our experiments demonstrate that this decrease in latency occurs during transmission through the nucleus VPL. No change in synaptic transmission time was observed in nuclei gracilis and cuneatus or in the cortex itself.

Introduction Both clinical and electroencephalographic features of congenital arteriovenous aneurysms have been extensively described by several authors.* Indeed, few new data could be provided, in our opinion, by a simple electroclinical description of a number of cases of arteriovenous aneurysms (AVA). Consequently, our present study will deal exclusively with some peculiar electrographic aspects of AVA, namely the occurrence of EEG abnormalities contralateral to the malformation. Possible pathophysiological mechanisms underlying this phenomenon will be suggested. Material and Method From a series of 23 cases of congenital arteriovenous aneurysms thoroughly investigated from the clinical, EEG, and radiographic standpoints, 4 cases were selected. A 16-channel Galileo Beta electroencephalograph and an 8-channel Alvar one were used. Recordings were taken according to the system of 10 to 20 electrodes placement recommended by the EEG International Federation. During the recordings, auditory (noise and/or whistle), visual and noxious stimuli, hyperventilation, and intermittent photic stimulation were carried out