FUNCTIONAL ASPECTS OF LOCALIZATION IN CATS TECTUM OPTICUM

Relationship between localization and functional properties of movement detecting single neurones was investigated in the cat's tectum opticum. Functional properties of single neurones were determined and locations of electrode tips marked with Prussian blue. Tectal units had their receptive fields located in the contralateral half of the visual field. Directionally selective units with preference for upward directed movements were located medial to a parasagittal division line of the tectum and had their receptive fields above the horizontal meridian of the visual field. Downward oriented preferred direction was correlated with recording sites in the lateral half of the tectum and with receptive field position below the horizontal meridian. Horizontal or oblique preferred directions of tectal units point to the contralateral side. The relationship between receptive field position and medial or lateral location of recording sites holds also for direction-independent movement-sensitive units. With increasing horizontal eccentricity of receptive field position the recording sites shift more posteriorly in the tectum. Receptive field position did not change within the same vertical penetration column, while receptive field size increased with increasing recording depth. Incidence of spontaneously active, directionally unselective and monocularly driven units was high in surface-near layers. Below the stratum opticum, most neurones were directionally selective, quickly adapting, responsive to stimulation of either eye and activated by tactile or acoustic stimuli. © 1969.