Supplementary Figure 9: Correlation of synaptic and bAP-induced Ca²⁺ activity in dendritic spines.

a, Red: mean action potential and PSP reported by QuasAr2; orange: mean spine-jRGECO1a fluorescence induced by bAP and sub-threshold synaptic inputs, respectively. b, Distribution of Ca²⁺ transient amplitudes in spines, induced by bAPs (red) or subthreshold synaptic inputs (brown). Synaptic inputs only drove Ca²⁺ transients in a subset of synaptic spines, while bAPs drove Ca²⁺ signals synchronously in almost all dendritic spines. c, Correlation of somatic PSPs and sum of Ca²⁺ transient amplitude across all spines (n = 14, R² = 0.42, P = 0.01). d, bAP failure in spines. Blue: 10 ms blue light stimulation of soma-localized CheRiff in a presynaptic cell. Red: postsynaptic QuasAr2 fluorescence; dark yellow: average over all the spines of spine-jRGECO1a fluorescence (n = 100 spines). Right: single-spine fluorescence traces within a single dendritic branch, corresponding to the regions circled in the figure. The orange trace shows an example of a bAP-induced spine Ca²⁺ transient distal to a spine that did not respond to the bAP. Scale bar, 15 μm. All shaded error bars, s.e.m.