Figure 6. Reward zone representation versus performance on the GOL task.

(a) Time-averaged images of the deep sublayer from two different recording sessions are shown in grayscale. Identified place cells from each session are overlaid and colored according to the distance of their centroid to the reward (green = near, purple = away). The mean distance to the reward zone is indicated (radians). (b) As in (4b), licking distributions from the two experiments corresponding to (a). (c) Mean distance of each place cell centroid to the reward on first and last days of the experiment. On the last day, the mean distance to reward was significantly different from the chance level of π/2 for both sublayers (dashed line; n=6 mice, one sample T-Test, deep: p<0.001, superficial: p<0.05), but was not significantly different between sublayers (n=6 mice, p=0.95, paired T-Test). Error bars indicate mean +/− s.e.m. across animals (d) We did not detect a relationship between distance to reward at the end of condition II with distance at the end of I, sublayer, or with the interaction [Type II ANOVA, n=172 deep, 336 superficial place cells, F(Distance end of I) = 0.10, p(Distance end of I) = 0.76; F(layer) = 0.54, p(layer) = 0.46; F(interaction) = 0.11, p = 0.74]. The dashed line represents the mean distance expected in the case of a uniform place field distribution, and error bars indicate mean +/− s.e.m. across cells. (e) Fraction of licks in reward zone (P) plotted against D_D (top) and D_S (bottom). Individual points represent single recording sessions. The dashed line indicates the linear fit with the 95% confidence interval shaded. We observed a significant relationship between D_D and P (n = 91 sessions, r= −0.40, p<0.001, Pearson’s r) but not between D_S and P (n=91 sessions, r= −0.15, p = 0.15, Pearson’s r). (f) In order to directly compare the sublayers’ relationships to performance on the GOL task, we compared the magnitude of the difference in correlation coefficients (0.25, dashed line) relative to a null distribution (see Methods). The true difference (dashed line) fell outside the shuffle distribution (p<0.001).