The computer-controlled screen monitor located 57 cm in front of the cat’s eyes was usually set at a luminance of 15 cd/m2 against a background of 1 cd/m2. The stimuli—elongated light bars were set at cell’s RF center. The extracellular action potentials from single neurons were recorded, conventionally amplified and monitored both visually and acoustically (via a loud speaker). To exclude multiunit data, special attention was paid to the shape and magnitude of the action potentials. Only identified single unit potentials triggered standard pulses which were then fed into a microcomputer for data collection.