When DSIs were calculated for preferred velocities before cooling, in most cells there were substantial (≥20%) changes (Figure 5E). In one cell, inactivation resulted not only in a big reduction in DSI but also in a 180° directional shift (Figure 5E*). Overall however, the mean DSIs of area 17 cells before (72.15 ± 31.3%; range: 17.0%–100%; n = 11) and during (68.25 ± 34.5%; range: 13.2%–100%) inactivation of PTV cortex were quite high (see Duysens et al., 1982a).