1). The percentages of orientation selective neurons (selectivity index > 0.33, i.e., peak:null response > 2:1) were similar in areas V1 (58/78 = 74%), PM (30/43 = 70%), and AL (31/40 = 78%). Our estimates of orientation selectivity did not depend strongly on stimulus spatial frequency (data not shown) and are not likely to depend on temporal

frequency (Moore et al., 2005). We next considered direction selectivity across areas. Strong direction selectivity (index > 0.33, i.e., peak:null response > 2:1) was evident in 69% of V1 neurons (54/78), as compared to 42% of PM neurons (18/43) and 15% of AL neurons (6/40). V1 neurons were significantly more selective for direction than PM neurons (p < 0.02, K-S see more test, Figures 5B and 5C and Table 2). Neurons in AL showed less direction selectivity than neurons in V1 (K-S test, p < 10−7) and in PM (p < 0.01). These differences in direction selectivity between V1, PM, and AL cannot be explained by differences in peak response strength, which did not differ across areas (Table 2, K-S tests, all p values > 0.4; see Discussion).

However, the lower direction selectivity in AL compared to PM and V1 may be explained by our use of different stimulus temporal frequencies (8 Hz in AL, 2 Hz in PM and V1; see Moore et al., 2005), which were chosen to provide comparable response efficacy in each area (Table S1). We also investigated whether responses in any of these areas were biased to specific orientations or directions. The average normalized response across all neurons showed found a significant bias (to upward and downward drifting stimuli) in area AL selleck chemicals llc (ANOVA across eight directions, p < 0.001; see Figure S5A). Similar results were observed when considering

the preferred orientations and directions of individual neurons in area AL (Figures S5B and S5C). Population directional biases were not as clear in areas PM or V1 (all p values > 0.1). Together, these data indicate strong differences in response tuning between areas AL and PM, which suggests that these areas make distinct contributions to different visual behaviors (see Discussion). We tested whether these differences in response tuning between areas were present both during trials when the mouse was stationary and trials when the mouse was moving on the linear trackball. For this analysis, we selected all neurons in which we obtained robust estimates of spatial and temporal frequency preference both while the mouse was “still” and “moving” (same criteria as in Figure 3; V1: n = 35 neurons, AL: 27, PM: 8; Experimental Procedures). Temporal frequency tuning curves for two representative neurons, during still and moving conditions, are shown in Figure 6A. Consistent with a previous study (Niell and Stryker, 2010), locomotion led to a significant increase in peak response amplitude in V1 neurons (76%; paired t test, p < 10−4; Figures 6B and 6C).