Figure 1. Summation of local synaptic inputs and global APs evoked by glomerular stimulation is mostly supralinear. A, Schematic depiction of experiment and example of individual experiment. Left, Stimulation of mitral cells via glomerular stimulation electrode, whole-cell recording of responses (EPSPs, APs) from GC, which is filled with Ca2+-sensitive dye via the patch pipette to allow for two-photon imaging of synaptic responses in individual spines. Right, bottom, Vm recording from GC soma with similar stimulation strength: EPSP or AP. Middle and top right, Fluorescence transients (line scans) across spine and adjacent dendrite. Four types of responses: 00, no substantial ΔCa2+ in spine or dendrite; 10, ΔCa2+ limited to spine; 01, similar ΔCa2+ in spine and dendrite; 11, larger ΔCa2+ in spine than in dendrite, ΔCa2+ in dendrite similar to 01. Middle, Two-photon scan of imaged spine and dendrite. B, The matrix of possible spine states with respect to ΔCa2+ as inferred from the responses: 00, no local input, no AP; 10, local synaptic input to spine head; 01, global AP without local activation; 11, coincident global AP and local activation. The associated ΔCa2+ is depicted as red intensity. C, Left, Cumulative scatter plot of n = 11 experiments. x axis represents arithmetic sum of spine ΔF/F amplitudes for AP and local input (10+01). y axis represents spine ΔF/F amplitudes for coincident activation 11. Right panel, SE (normalized amplitudes 11/(10+01)). Mean and individual values of coincident activation (c) compared with arithmetic summation (as). Error bars indicate SD. *p < 0.05. A, Left, Scheme modified from Egger et al. (2005). Right, Modified from Egger (2008). C, Left, Reanalyzed from Egger (2008) with additional data from two more spines.