Figure 5. Firing rate changes induced by visual landmark manipulation.

(a) For each cell from left to right: Spike-time autocorrelation, HD tuning curves during vp1 (black) and vp2 (blue) trials, instantaneous firing rates (standard deviation Gaussian kernel 25 s, window size 1 s) as a function of time, mean firing rate during vp1 and vp2 trials, and firing rate maps during vp1 and vp2 trials. Numbers above the histograms indicate the relative change in rate. Numbers above the firing rate maps are peak firing rates. (b) Left: Scatter plot of the theta index of each HD cell against its relative firing rate change across trial types. Right: Relative firing rate change between vp1 and vp2 trials for non-rhythmic and theta-rhythmic HD cells. (c) Pie charts illustrating the percentages of non-rhythmic (left) and theta-rhythmic (right) HD cells with significant changes in preferred direction, HD score or mean firing rate. ***: P $<$ 0.001.

Figure 5—figure supplement 1. Non-rhythmic HD cells appear to encode allocentric HD rather than egocentric landmark bearing.

(a) Allocentric HD tuning curves of a HD cell measured across nine different quadrants within the arena during vp1 trials. Numbers above polar plots show peak firing rates. The location of the visual landmark (vp1) and the cue card are indicated. (b) Egocentric landmark bearing tuning curves relative to the landmark of the same cell. These curves display the firing rate of the cell as a function of the angular position of the landmark in the animal’s field of view. The üp’ direction of these plots corresponds to the animal’s head pointing directly at the landmark. Here, egocentric tuning curves changed as a function of position as expected from an allocentric HD cell. (c) Variance in allocentric and egocentric preferred direction across the nine quadrants for all non-rhythmic HD cells (paired Wilcoxon rank-sum test, N = 34, v = 166, p=0.02). This figure panel shows that allocentric HD tuning was more constant than egocentric tuning and suggests that non-rhythmic HD cells appear to encode allocentric HD rather than egocentric landmark bearing. *: p $<$ 0.05.