Analysis of visual information in midbrain centers.

The role of pretectum and colliculus superior in the analysis of visual information was studied. Single unit responses to visual stimuli were recorded. Several types of responses were observed, including "suppressed by contrast", "direction non-sensitive" and "direction sensitive" responses. An attempt was made to define the place and mechanism of direction-sensitivity of the cell. The conclusion is put forward that horizontal cells in the first layers of retina are not responsible for direction-sensitivity. Detailed analysis of receptive field structure revealed "homogeneous" and "heterogeneous" types of receptive fields as shown by response patterns of the neuron to a flashing light spot positioned in different parts of the receptive field. Study of latency distributions also revealed both complex "heterolatent" and more simple "homolatent" organizations of receptive fields The effect of the intensity of background illumination was investigated. Results show that changing of the background illumination can influence the response pattern of a cell, and sometimes can influence the direction-sensitivity.