Extended Data Fig. 2: The contribution of the directional preference of the thalamic charge to the direction selectivity index of F1Thal.

a, The same plot as in Fig. 1g, right. The data points for which QThal and F1Thal prefer the same direction (positive values on the y axis) are shown in red; data points for which QThal and F1Thal prefer opposite directions (negative values on the y axis) are orange. Note that the average absolute value of DSI QThal is slightly but significantly larger for the red data points (red points: 0.087 ± 0.053; n = 32; orange points: 0.048 ± 0.037; n = 20; P = 0.003; t-test), indicating a slight bias of QThal in the preferred direction. To determine the effect of this slight bias in thalamic charge on DSI F1Thal, we have equalized the thalamic charge evoked by gratings drifting in both directions (see b–d). b, Example recording from a cortical neuron for which the charge of thalamic excitation is larger in the preferred versus the non-preferred direction of F1Thal. Top, thalamic excitation as recorded (non-equalized) in response to a grating drifting in the preferred (left) and non-preferred (right) direction. Bottom, same as top but after scaling the response to the non-preferred direction such that the charge is the same in either direction (charge equalization). c, Cycle average of thalamic excitation with superimposed sinusoidal fit (red). Top, as recorded; bottom, after charge equalization. After charge equalization the direction preference is maintained but, for this particular example, the DSI is reduced (see filled data point in d). d, Scatter plot for all recordings (green points indicate DSI F1Thal >0.3; blue points indicate DSI F1Thal < 0.3). The filled data point is the example above. The equalization leads to only a small change in DSI F1Thal (all points: 0.28 ± 0.20 before and 0.26 ± 0.21 after equalization; P = 0.034; paired t-test; n = 66; green points: 0.49 ± 0.15 before and 0.46 ± 0.17 after equalization; P = 0.022; paired t-test; n = 25; blue points: 0.16 ± 0.09 before and 0.14 ± 0.11 after equalization; P = 0.300; paired t-test; n = 41).