Some Behavioural Correlates of the Transcephalic d.c. Potential in Cats

Abstract

NEURAL direct current (d.c.) potentials have recently received much attention¹. A steady d.c. potential across amphibian cortex in a fronto-occipital plane has been observed². These measurable exterior surface potentials are correlated with anaesthesia and sleep^3,4. High correlations have been reported between transcephalic d.c. potential (measured between mid-forehead to low union), level of anaesthesia and electro-encephalograph (EEG)⁵. In the awake state the surface-recorded steady potentials are frontally negative, while in anaesthesia the frontal negativity decreases, that is, the forehead becomes more positive with respect to the occiput. The general relationship between EEG activity and behaviour (sleep–wakefulness) of humans and animals is, of course, well known^6,7. This correlation of behaviour and EEG breaks down following the administration of anticholinergics such as atropine⁸. The EEG activity is slowed, whereas the animal appears excited. Such dissociation of EEG and behaviour under atropine has been observed in cat⁹, dog¹⁰ and rabbit¹¹.