In a substantial proportion of cases (6/15, 40%), cooling of PTV resulted in decreases in the magnitude of spike-responses to particular visual stimuli as well as increases in the magnitude of spike-responses to some other visual stimuli. Thus, in one cell, small significant reductions in the magnitude of spike-responses to optimally oriented moving light bar were accompanied by stimulus-direction dependant, significant increases in response to para-optimally oriented moving light bar (Figure 3Ai,ii; see effect on Orientation-tuning). Similarly, inactivation induced reductions in the magnitude of spike-responses to a light bar moving in one direction were accompanied by large and significant increases in the magnitude of spike-response to the same stimulus moving in the opposite direction (Figures 4A,B; see effect on Direction selectivity). The direction sensitive enhancement of response was even greater at higher velocities (Figures 4A,B; see effect on Direction selectivity and Preferred velocities).