Before inactivation, the mean background activity of simple cells at 0.23 spikes/s (±0.48; range: 0.01–1.33; n = 7) was almost identical to that (mean: 0.25 ± 0.50; range: 0.01–1.37) during inactivation. For complex cells, their control mean background activity (1.22 ± 1.98 spikes/s; range: 0.19–4.19; n = 4) was slightly higher than that (1.05 ± 1.55; range: 0.18–3.38) during cooling and substantially higher than that of simple cells (see Huang et al., 2007).