Figure 9.

Most head direction-only cells also encode angular velocity (83%) and some anticipate movement. Top left, Polar plot (blue line; firing rate/6° head direction) for one example cell that is motion modulated. Bottom, Occupancy data and number of spikes are binned according to linear velocity (vertical axis) and head angular velocity (horizontal axis; positive head angular velocity corresponds to a right turn), then converted to firing rate. Cells were classified as having a preferred self-motion state if the self-motion maps for two behavioral sessions were significantly positively correlated (99th percentile of random shuffled distribution). Self-motion maps from two behavioral sessions and corresponding correlation values are shown for this example cell. Max firing rate is in maroon text. Top right, Some of the turn × head direction cells, including this example, also anticipate movement (30%). Cross-covariance between preferred self-motion and cell activity revealed that this head direction-only cell anticipates right turns. This cell had a right turn preferred self-motion state so angular velocity was used. The positive correlation before time 0 indicates anticipation of a right turn by ∼125 ms. Red horizontal lines denote the 95% confidence interval calculated from spike-jittered data for this same cell.