using robust regression (MATLAB function ‘robustfit.m’) of ΔF/F0_spine vs. ΔF/F0_dendrite (the slope of the fitted line in Supplementary Fig. 11b). Third, the visual responsiveness (ΔF/F0 > 10%) and the OSI of individual spines were calculated with the BAP signal removed. Active spines (Fig. 4f) were defined as spines showing at least three spine-specific (i.e., BAP independent) calcium events during the 5 minute imaging session, with an event defined as an episode of the calcium signal that crosses 3 s.d. of the baseline noise for at least three consecutive frames (∼50 ms).
