Extended Data Figure 9. Mapping retinotopy using individual neurons vs. widefield signals.
(a) The stimulus used for retinotopic mapping was a sparse random pattern of white and black squares on a grey background (top). The fluorescence time-course from the entire field of view was used to compute a global stimulus-triggered average response elicited by changes in luminance at each position. The centre of mass of this global receptive field (RF) was used to constrain the fits of widefield and neuronal RF to the appropriate retinotopic region. (b) Maximal projection from an example field of view. In this example, the field of view was subsampled in a grid of 9×9 regions of interest (ROIs, red squares) to compute widefield RFs. Scale bar: 100 μm. (c) The widefield RFs calculated for the ROIs in b, normalised to their maximum. The widefield RF centres from the grid of ROIs were interpolated to estimate a retinotopic map, assigning a widefield RF to each cortical location, whether it contained a responsive neuron, an unresponsive neuron, or neuropil. (d) Estimation of neuronal RFs. ON (red) and OFF (blue) receptive fields were estimated by regularised smooth pseudoinverse regression using either streams of white (ON) or black stimuli (OFF) as predictors, and assuming a common response kernel across neurons. ON and OFF subfields were then combined to estimate the RF centre (green dot). RF were considered significant if the cross validated correlation coefficient between predicted (red trace) and actual response (black trace) was greater 0.2. (e) Azimuth of neuron RF centre vs. widefield RF centre for all excitatory presynaptic neurons (black dots, n = 113, rpre = 0.89, p r_pre = 2.8*10-39, linear correlation, F-test) and surrounding excitatory neurons (red density, n = 25677, rall = 0.88 p r_all < 10-308, linear correlation F-test) across experiments. (f) Same as e for elevation (rpre=0.80, pr_pre= 9*10-27; rall = 0.85, p r_all < 10-308). (g,h) Same as e and f for presynaptic inhibitory neurons (black dots, n = 37, rpre=0.92, pr_pre=1.3*10-15, for azimuth; rpre=0.71, pr_pre=9.7*10-7, for elevation) and all inhibitory neurons (n = 1963, rall=0.95, pr_all < 10-308, for azimuth; rall=0.74, p r_all < 10-308, for elevation).