This additional stimulation caused several of these cells to reverse (Figures S2E and S2F), indicating that stable cells can become reversed cells. Second, we compared the tuning properties prior to adaptation of the cells that reversed and http://www.selleckchem.com/products/chir-99021-ct99021-hcl.html those that remained stable, and we found that the stable cells tended to be more sharply tuned (the DSI values for stable cells were 0.78 ± 0.19 and for reversed cells were 0.63 ± 0.23, mean ± SD; p < 0.02, Mann-Whitney test; the vector sum magnitude values for stable cells were 0.53 ± 0.17 and for reversed cells were 0.38 ± 0.17, p < 0.01, Mann-Whitney test; Figures S2G, S3A, and
S3B). This suggests that cells are more difficult to reverse when their original tuning is sharp. Third, both stable and reversed cells responded to adaptation by significantly reducing their
firing rates to the original PD (from Veliparib order 9.95 ± 5.42 Hz to 2.73 ± 2.68 Hz for reversed cells, p < 0.01 and from 10.38 ± 8.53 Hz to 5.85 ± 5.31 Hz for stable cells, p < 0.02, Mann-Whitney test; Figures S2G and S3C, examples in Figures S2A and S2B). In addition, there was no correlation between a cell’s ability to reverse and the age or genotype of the mouse (Figures S3D and S3E). Altogether, these data suggest that DSGCs that remain stable and those that reverse are not inherently different but rather their likelihood to reverse depends on their initial tuning. Combining the data across all stimulation protocols and categorizing the results from their final DS tests, we found
that most cells significantly altered their directional tuning after exposure to an adaptation protocol (30/74 DSGCs reversed, 15/74 became ambiguous, and 29/74 remained stable). Interestingly, regardless of the adaptation protocols, none of the cells acquired a preference for the direction orthogonal to the original P-N axis. Instead, the PD after adaptation was either close to the original PD (for stable cells) or very towards the original ND (for reversed cells, Figure 2J). To investigate the stability of the reversal, we used a subset of cells for which we maintained recordings and continued to perform DS tests after the reversal. All cells in these experiments maintained their reversed directional preference for the extent of the recording (ranging from 2–23 min, n = 9 cells). Thus, the reversal induced by visual stimulation is apparently robust and long lasting. Direction selectivity is dependent on GABA-A receptor-mediated inhibition (Ariel and Daw, 1982; Caldwell et al., 1978; Kittila and Massey, 1997; Massey et al., 1997; Wei et al., 2011). To determine whether this inhibition also mediates the newly acquired PD, we bath applied a GABA-A blocker (gabazine, 5 μM) after the directional preference of GFP+ DSGCs was reversed.