Supplementary Figure 2: Distal activation in the absence of visual stimuli

(a) Silicon probe electrodes were placed in the binocular zone (BZ) and/or in the monocular zone (MZ). Activity in the BZ was elicited antidromically through contralateral laser stimulation. (b) Selectivity for retinotopic position of three units recorded simultaneously with multi-shank electrodes (shank spacing 400 μm), in BZ (green), and in MZ (black). (c) Firing rate responses of the BZ unit to callosal stimulation. Bin width was 12.5 ms. (d,e) Same, for the MZ units (recorded simultaneously). Note different vertical scale. (f-h) Averaged firing rate response for the three retinotopic positions. Activity was averaged first among units on the same shank, then among all the shanks within the same retinotopic position (callosal BZ: n = 9 shanks from 19 animals, acallosal BZ- near MZ: n = 11, far MZ: n = 14). Shaded areas indicate standard error of mean. Scale bars are in spikes/s. (i-k) For units where activation was significant, we measured the activation peak (the maximum of the response curve, i), half width (the duration when the response curve was above 50% of the peak, j) and onset latency (the first time when the response curve reached 50% of the peak, k). Open circles are for units in superficial layers, and closed circles for units in deep layers. To make all data points visible, a small random fluctuation was imposed on the horizontal position of each data point. The activation peak was significantly larger in callosal BZ ( (i) inset, n = 44, p < 0.05, Mann-Whitney test) than in acallosal BZ-near MZ (n = 45) or in far MZ (n = 76).