Figure 7.

Conjunctive cell activity anticipates movement toward the cue while ECD-only cells reflect the current position of the cue. A, Examples of three conjunctive cells illustrating that conjunctive cells typically anticipate movement with either long latency (nearly 1 s, left and middle columns) or short latency (175 ms; right column). Top, Firing rate for ECDs (blue bars; 6° bins). Middle, Occupancy data and number of spikes are binned according to linear velocity (vertical axis) and head angular velocity (horizontal axis), then converted to firing rate. Max firing rate ranges from 0 (dark blue) to the peak value indicated in maroon. Bottom, Cross-covariance between preferred self-motion (e.g., for a right turn cell like 1 or 3 firing rate was cross-correlated with angular velocity) and cell activity revealed that conjunctive cells anticipate movement. Red horizontal lines denote the 95% confidence interval for head angular velocity (not linear velocity) for the same cells. The confidence intervals were generated from jittering spike times a random amount between ±1.5 s, calculating the cross-covariance, repeating this process 1000 times, then collapsing across lags for the complete shuffled cross-covariance dataset and calculating the 95% confidence interval. B, Most ECD-only cells show the opposite pattern, turning precedes activity, suggesting turning into the ECD receptive field. C, Tuning for the population of cells with ECD properties is distributed to the sides of the rat (mean vector = 91°, p ≤ 0.01; left hemisphere green; right hemisphere orange). Black semicircles indicate approximate rat visual field (Adams and Forrester, 1968). Note, some cells with tuning toward the periphery of the visual field wrap to the opposite visual field so that the mean tuning direction is behind the rat and outside of the visual field (e.g., A # 3 and Fig. 3A # 2). D, Population data are consistent with examples shown in A and B. A significantly higher proportion of conjunctive cells were active before movement than ECD-only cells (χ² ₍₁₎ = 21.3, p < 0.0001). E, Mean (±SEM; shaded) cross-covariance for conjunctive cells that were active before movement (black; left) and ECD-only cells that were active after movement (green; middle). The population data confirms the single-cell examples illustrating that the population of conjunctive cells anticipates movement with either short or long latency (apparent as two bumps on the population plot at approximately −1 s and −175 ms) while turning tends to precede activity for ECD-only cells with short latency.