Possible Influences of Barbiturate Anesthesia on Cerebellar Operation: a Computer Simulation Study

Abstract

A network model of the mammalian cerebellar cortex is used to examine the possible influence of barbiturate anesthesia on the cerebellar response to mossy fiber inputs. It is proposed that barbiturates reduce the background level of mossy fiber input as well as depress the excitability of Purkinje cells to parallel fiber inputs. The effects of parameter modifications reflecting these actions are examined by introducing simulated parallel fiber and mossy fiber inputs into the network. Transient changes in Purkinje cell activity induced by brief inputs of either mossy or parallel fiber origin are shown to be relatively insensitive to the parameter modifications made to simulate the effects of barbiturate anesthesia. In contrast, mossy fiber inputs of longer duration lead to very different temporal patterns of Purkinje output when these parameters are varied. Despite rather large changes in parameters, an off-beam inhibitory action of basket cells is predicted in all cases. It is concluded that while the temporal and spatial organization of the cerebellar response to mossy fiber inputs may be altered by barbiturates, these alterations may be overlooked if observations are limited to the discharge patterns of single neurons evoked by brief electrical stimuli. On the basis of simulation findings, three experimentally-testable hypotheses are proposed and a new role for reticulo-cerebellar input suggested.

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Notes on contributors

James A. Mortimer

Joyce Laing works in the Department of Child and Family Psychiatry, Playfield House, Cupar, Fife, and is a Consultant Art Therapist to Psychiatric Hospitals and Prisons and Chairwoman of the Scottish Society of Art and Psychology