Locomotion speed is encoded in superficial layers of mouse V1 with a non-uniform distribution biased towards layer 4

Stringer et al. used two-photon calcium imaging to record activity from tens of thousands of V1 cells in head-fixed mice during a visual orientation discrimination task, and showed that the neural response encodes stimulus discrimination thresholds nearly 100 times more precise than the corresponding behavioral thresholds. Animal arousal state was monitored by measuring the locomotion speed during task execution, but could not explain this large discrepancy in discrimination threshold. Here, we take advantage of the fact that the behavioral data was acquired in that experiment, and ask whether we are able to show that the locomotion speed is encoded in V1 neural activity. We perform a logistic regression on the neural responses, and show that it is able to distinguish “passive” states from “running” states with very high accuracy; a linear regression on the same dataset is able to extract the precise locomotion speed with similar accuracy. Importantly, we show that the subset of cells with larger model coefficients is not uniformly distributed in the recorded V1 cortical volume, exhibiting instead a clear bias towards layer 4 and away from layer 2/3. While these observations appear to agree with previous investigations, which are consistently able to detect effects on cell membrane potentials or activity patterns in layer 4 in V1 due to locomotion, we believe our approach adds an important dimension by attempting to characterize the laminar distribution of the locomotion speed information density in V1.