Figure 8. Modification of directional selectivity in a simple cell recorded in a 5-week-old kitten.

This receptive field was studied using stationary (left panel) and moving (right panel) stimuli. The fifth position (arrow) was submitted to 50 pairing trials (data not shown) during which the ‘on’ response was associated with a positive current (S⁺, +4 nA) and the ‘off’ response with a negative current (S⁻, -10 nA). After pairing, static ‘on’ responses were increased while ‘off’ responses were depressed (see histograms of cumulative ‘on’ and ‘off’ responses after pairing where the superimposed dotted lines represent the initial control responses). The GCRs shifted from 0.61 to 0.76 (P < 0.023) and the LCRs were significantly modified (P < 0.001) in 2 positions. Calibration bars: 1 s; 10 AP s⁻¹; 0.5 deg. In the right panel (Dynamic) light and dark bars were moved in opposite directions across the RF. The empty and filled downward and upward histograms represent the visual responses to the bright and dark stimuli, respectively. The responses in the opposite direction are shown in a mirror-like fashion and aligned on the same positional axis in the RF. This simple cell showed a directional preference before pairing which reversed when the contrast of the stimulus was inverted. A significant change in the response to the dark bar was observed after pairing, whereas the response to the light stimulus remained the same. Calibration bars: 1 s; 20 AP s⁻¹.