Sleep patterns in the pony with observations on partial perceptual deprivation.

Sleep patterns in the pony wlth obse~anons on partial perceptual depniva. ~ton. PHYSIOL. BEHAV. 12(5) 789-796, 19"74.-Sleep characteristics were invest~ated m ponies under normal stall conditmns and during partial (visua~ and auditive) perceptual deprivation. Polygraphic recordings of slow waves sleep (SWS) and paradoxical sleep ('PS) including changes in hippocampal acnvity are described. A notable feature was the modulation of :hythmlc slow hippocampal activity during PS. Sleep patterns are described with a relatively short sleep cycle qmem-1: 13.$ rain). An intermediary phase tiP), lasting about 2.0 rain, frequently occurred (40%) between SWS and PS. Perceptual deprivation reduced the occurrence of IP but an increase in SWS was observed. After-effects showed an augmentation in both SWS and PS. Sleep Equidae Hippo,.ampal theta rhythm Intermediary phase Perceptual deprivation THE DEMONSTRATION of the existence of slow wave sleep (SWS) and paradoxical sleep (PS) in most mammals encouraged the view that sleep is more than a state of rest accompanied by reduced responsiveness to the external environment. It drew attention to the question of the biological value of sleep, the understanding of which requires careful analysis of neurolo~cal as well as behavioural aspects. Much more has been done on the behaviour of man and animals dur/ng prolonged exposure to a monotonous sensory environment but the literature contains only a few studies of sleep under these conditions [ 6,12 ], all of which have been conducted on man. In their review on sleep and learning, Bryson and Schacher [2], suggested that sensory deprivation is unfamiliar to adult mammals and thus should theoretically cause increased subsequent sleep. So, such a study may be of relevance to some theories on the function of sleep, specially those relating SWS to physical fatigue and PS to cognitive functions. In the present experiment sleep patterns are exammed in ponies under normal stall conditions and during a period of partial perceptual deprivation. Five male Pottock ponies ranging from six months to six years of age were chronically implanted with electrodes in the following manner: under pentobarbitone Na anaesthesia (20 mg/kg) epidural silver coated screws were positioned bilaterally over the frontal, parietal and occipital regions of the cerebral cortex. Pairs of stainless steel wires (dia. 0.1 ram), insulated with enamel except for I mm at the tip, were inserted stereotaxically into the dorsal hippo-campus, the stereotaxic coordinates being obtained on the basis of Yoshikawa's anatomical atlas [18]. The exact positions of the electrodes …