The electrocorticogram in the chronic cerveau isolé cat

The effect of nociceptive and proprioceptive stimulation revealed the possibility of an extraneural pathway which affected the ECoG of the isolated cerebrum of high mesencephalic, chronic cats which survived for an average of 48 days.

Abstract

1. The ECoG of cerveau isolé preparations was studied in 16 high mesencephalic, chronic cats which survived for an average of 48 days. Relationships were sought between ECoG and the level of behavioral arousal and with the electrical activity at the brain-stem caudal to the transection. 2. In the acute stage, two ECoG patterns could be distinguished: spindle bursts or discontinuous slow waves; and continuous, high voltage slow activity. In chronicity, this pre-collicular forebrain exhibited low voltage, fast desynchronized rhythms (ECD) which lasted for several hours and which were similar to the ECD patterns of an intact cat. 3. Periods (mean duration 60 ± 4 min) of high voltage, continuous slow synchronized rhythms (ECS) alternated with ECD in the chronic preparation. These cyclical lapses exhibited electrocortical synchronization; i.e., sleep period (ECSP), which closely resembled the ECoG of slow sleep in the normal cat. 4. Since both ECD and ECS persisted following visual and olfactory deafferentation of the cerveau isolé, both patterns probably have an autochthonous origin in the structures of the rostral forebrain. 5. Olfactory stimulation desynchronized the ECoG according to the stage of the ECSP during which stimulation was presented. Maximal desynchronization was observed during the onset stage of the ECSP. 6. The EEG patterns of the cerveau isolé showed no systematic relationship with the level of arousal of the animal, nor with the electrical activity in the brain-stem. However, the effect of nociceptive and proprioceptive stimulation revealed the possibility of an extraneural pathway which affected the ECoG of the isolated cerebrum. 7. The possibility of the existence in the forebrain of the cat of an autochthonous tonic, mechanism capable of independently evoking a cyclic alternation between wakefulness and slow sleep is discussed.