Extended Data Fig. 10: Branch-specific boosting analysis.

a, Two additional examples of branch-specific local events in response to photostimulation of identified presynaptic targets in LM. Left, average image of global events, showing stimulated (incl. spine) and reference branch ROIs. Middle, spines responsive to feedback. Right, average image of single trial showing branch-specific event. b, Fluorescence extracted from those ROIs, showing the variability of stimulated vs reference branch signal strength and the branch-specific events driven by photostimulation, indicated by red bars. c, Top, schematic illustrating ideal layout of ROIs used for boosting analysis. Bottom, distribution of minimum distances between stimulated branch ROIs and the identified feedback-recipient spine. d, Mean boosting indices for blank vs photostimulation trials. Each recording appears once for “near” ROIs and once for “far”. “Near” ROIs same as reported in Fig. 4. Filled circles are individually significant neurons (t-test, p < 0.05). Right, same data plotted as a histogram of differences between boosting indices measured during stimulation and during blank trials. e, Boosting index (difference between photostimulation and blank, same data as in Fig. 4) as a function of retinotopic distance between target location and parent soma location. f, Schematic illustrating visual stimulation delivered simultaneously with feedback stimulation. g, Boosting indices measured from Near ROIs while the visual stimulus was a grey screen. Left, scatter plot of indices measured on blank vs on stimulation trials. Right, same data shown as a histogram of differences between trial types. h, Boosting indices measured from Near ROIs while the visual stimulus was an inverse grating positioned around the receptive field of the V1 neuron. Left, scatter plot of indices measured on blank vs on stimulation trials. Right, same data shown as a histogram of differences between trial types.