The relationship of receptive field properties to the dendritic shape of neurones in the cat striate cortex.

In this study, we examined the hypothesis that some features of the receptive fields of cortical neurones are determined by the extent to which their dendrites can sample from different parts of the visual field representation on the cortex. In particular, the orientation selectivity and size of the receptive fields of cortical neurones were examined for their relationship to the tangential organization of the dendrites of cortical neurones. Single neurones in the visual cortex of anaesthetized and paralysed cats were physiologically characterized and injected intracellularly with horseradish peroxidase (HRP). In some cases it was possible to identify whether the neurones received direct (monosynaptic) or indirect (polysynaptic) input from afferents of the lateral geniculate nucleus. The dendritic arborizations of the HRP-filled cells, sampled from all layers, were reconstructed in three dimensions with computer assistance, and rotated to give the tangential or surface view. The bias in the tangential arrangement of the dendrites was determined by calculating the mean vector angle for the distribution of the dendrites of each cell. This bias was related to the orientation selectivity of the neurones. There was no consistent relationship between orientation selectivity and the tangential bias of the dendritic tree. The width of the receptive fields was compared to the equivalent 'width' of the tangential extent of the dendrites. There was no significant relationship between the two widths. The tangential arrangement of the dendritic field does not appear to be important in determining the orientation selectivity or the size of the receptive fields of neurones in the cat visual cortex. The former feature of the receptive fields may be determined by inhibitory processes, while the extent and number of the afferents providing input to a single neurone may determine the latter property.