Single-neuron responses to moving sine-wave gratings in the pigeon optic tectum

Abstract

The responses of single cells in the superficial layers of the pigeon optic tectum to moving sine-wave gratings were analysed quantitatively. From these responses, cells could be identified as modulated or non-modulated. About 80% of the units tested were found to be spatial frequency dependent. Some cells have spatial frequency tuning curves with both high- and low-frequency response cutoff: others have only a high-frequency cutoff. Directional and nondirectional cells showed no differences in responses to gratings. No correlation was found between the optimal spatial frequency response and either the size of the receptive field or retinal eccentricity. Responses could be greatly affected by contrast. The inhibitory surround has no effect upon the specification of the cell spatial selectivity. The higher resolution value for square-wave gratings at 60% contrast was 7 c/deg. These findings suggest that tectal cells in pigeon may be able to code spatial information.