Topography of the Potential Fields produced by Action of a Parallel Fiber Volley on Purkinje Cells

Abstract

This topographical analysis is designed in order to discover the functional meaning of the known connexions onto Purkinje cells. By means of the crossing-over synapses on the dendritic spines, a narrow beam of excited parallel fibers would act directly only on those Purkinje cells whose dendrites lay in its path. By contrast there would be an extensive transverse spread, for as far as 1000 μ from the beam, of the influence exerted on Purkinje cells indirectly through the basket and stellate cells. In an attempt to give a meaningful interpretation of this pattern of action on Purkinje cells, Szentágothai (1963, 1965 a) postulated that the crossing-over synapses on the dendritic spines are excitatory and that the basket cell synapses are inhibitory, so giving a wide zone of inhibition on each side of the excited zone on-beam. An independent physiological investigation corroborated this postulate of an inhibitory action of basket cells on Purkinje cells (Andersen, Eccles and Voorhoeve, 1964), and there is more recent evidence that the outer stellate cells also inhibit Purkinje cells (Eccles, Llinás and Sasaki, 1966 b, 1966 e; Eccles, Sasaki and Strata, 1966).