ELECTROPHYSIOLOGICAL AND BEHAVIOURAL CHANGES OWING TO SPLITTING OF BRAIN-STEM IN CATS

1. 1. A midline pontine split induced a persistent alteration of sleep-wakefulness rhythms in cats; sleep (synchronized and desynchronized) was drastically reduced, reaching mean percentages of 16.7% (synchronized sleep) and 4.4% (desynchronized sleep). Wakefulness remained persistently very high (78.9%). These changes lasted 3-5 weeks after the splitting procedure. Similar changes in sleep and wakefulness were observed after bilateral pontine splits at 3 mm from the midline, in which the pontine raphe nuclei were spared, and after unilateral longitudinal pontine section at 1.5-2 mm from the midline. 2. 2. A midline bulbar split did not cause any consistent change in the sleep-wakefulness cycle of the cat. A mesencephalic split significantly reduced the amount of desynchronized sleep whilst synchronized sleep was not modified. An apparent blindness was observed in this preparation. 3. 3. Marked alterations in behaviour, such as restlessness and hyperirritability, together with a marked loss of body weight, were observed in cats with severe sleep deprivation induced by pontine splitting. 4. 4. The retrograde changes in the aspecific brain-stem neurones brought about by midline and bilateral pontine splits suggest the hypothesis that the persistent increase in wakefulness and reduction of sleep (synchronized and desynchronized), induced by these cuts, may be ascribed to suppression or reduction of the flow of physiological sleep impulses (synchronizing and desynchronizing the EEG) originating in regions at the level of the pontine section or caudally to them, and ascending contralaterally to diencephalic and cortical regions. © 1969.