Figure 4. Differential potentiation and depression of ‘on’ and ‘off’ responses of a complex cell recorded in a 6-week-old kitten.

Conventions are as in Fig. 3. PSTHs are shown in the left panel for the paired position, and in the right panel for the unpaired position. Before pairing, a small ‘on’ response and a dominant transient ‘off’ response were observed in the two test positions. During pairing the ‘on’ response was increased to a high level using a +3 nA current pulse for 1500 ms (S⁺), whereas the dominant ‘off’ response was paired with a -4 nA current pulse of the same duration (S⁻). A significant change in the LCR was found in the paired position following pairing (P < 0.002), indicating a potentiation of ‘on’ responses of short and medium latency (100-300 ms) and a depression of ‘off’ responses. This finding is illustrated in the lower histogram (Diff) given by the difference, bin by bin, of the PSTHs after and before pairing (gain upward, loss downward). Calibration bars: horizontal, 1 s; vertical, 10 AP s⁻¹.