ELECTROENCEPHALOGRAM OF DIFFERENT CORTICAL REGIONS OF NORMAL AND ANAESTHETIZED CATS

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Abstract
E.E.G. tracings from more than 80 cats were obtained through tubular concentric electrodes planted in the skull so that the central Ag wire leads were in contact with the dura or pia mater. Comparison of various combinations of leads showed that the most detailed tracings were obtained when the input leads of the apparatus were connected between a stigmatic lead and its concentric tubular shell, the latter being a relatively indifferent electrode. Recognizable differences were observed in tracings from frontal, occipital and temporal regions, from the vertex and the ventral surface of the pyramids which were intensified in the sleeping cat, in both normal and anaesthetic sleep. A definite sequence of patterns occurred as the cat drifted into sleep, the first indication being high amplitude 5-7/sec. waves from the occipital region. These gave way in deeper sleep to random slow waves mingled with the frequency of the resting pattern. The next conspicuous change was the appearance from frontal leads of spindles of high amplitude 12-14/sec. waves, with random slow waves in all leads. Waking a sleeping cat restored the normal pattern. Activation patterns were demonstrated in normal resting animals and in lightly anaesthetized ones in response to a variety of stimuli. Habituation to a particular type of stimulus was easily demonstrated when the stimulus was repeated at short intervals. When habituation resulted in the absence of an activation pattern in response to a given stimulus, a different type of stimulus was immediately followed by activation.