Figure 3. Preparatory Activity in GC.

(A) Schematic of trial structure. The gray bar highlights the temporal window (1 s) used to analyze preparatory activity. Time 0 represents the first lick to the lateralspout.

(B) Raster plots and PSTHs of two representative neurons showing direction-selective, preparatory activity. The neuron on the left (neuron no. 1) displays higherfiring rates during the delay period preceding left licks (blue ticks and blue line for raster plot and PSTH, respectively); the neuron on the right (neuron no. 2) displays higher firing rates in anticipation of right licks (red ticks and red line for raster plot and PSTH, respectively). Time 0 represents the first lick to the lateral spout.

(C) Histogram of direction index during the delay epoch. Blue and red bars represent neurons with a direction index significantly <0 or >0, respectively. Gray barsrepresent neurons with no significant direction index (similar firing rate between left and right correct trials).

(D) Heatmap showing the time course of the direction index. Each row represents a single neuron (only neurons with significant direction index are shown). Time0 is the first lick to the lateral spout. Blue and red represent negative (leftward) and positive (rightward) direction indices. White traces superimposed on the heatmap represent the average direction index for neurons with negative (bottom) and positive direction index (up).

(E) Raster plots and PSTHs for one neuron showing preparatory activity and taste selectivity during the delay epoch. On the left (left trials), raster plot and PSTH for S (brown) and Q (green) trials is shown; on the right (right trials), raster plot and PSTH for M (gold) and SO (blue) trials is shown. Time 0 is the first lick to the lateral spout.

(F) Scatterplot showing the relationship between max taste selectivity and the absolute value of direction index. Each dot (pink and gray) represents a neuron withsignificant direction index (p_y < 0.01); gray dots represent neurons that also show taste selectivity during the delay epoch (p_x,y < 0.01). The gray dot with the red arrow represents the neuron shown in (E).

(G) Time course of classification accuracy for correct and error trials (black curve). Time 0 represents the first lick to the lateral spout. The red dashed curverepresents classification accuracy at chance level when the correct/error trials are shuffled. The thick horizontal black bar represents times with classification accuracy that is significantly higher than chance level (permutation test; p < 0.001). Shading represents the 99.5% confidence interval.

(H) Scatterplot showing direction index in correct and error trials. Each dot represents a neuron with significant direction index in correct trials. Orange points represent neurons that also show significant direction index in error trials. Gray-shaded areas highlight the quadrants in which neurons have direction indices with the same sign in correct and error trials, regardless of the gustatory cue. The red arrow indicates the neuron shown in (I).

(I) Raster plots and PSTHs for neuron no. 2 in (B), showing direction indices with the same sign in correct and error trials. Time 0 is the first lick to the lateral spout.Left: raster plots and PSTHs for correct (left licks, dark blue) and error (right lick, light red) trials in response to S and Q are shown. Right: activity for correct (right lick, dark red) and error (left licks, light blue) trials in response to M and SO are shown.

See also Figures S2 and S3.