Supplementary Figure 4: Estimation of the number of independent boutons.
From: Thalamus provides layer 4 of primary visual cortex with orientation- and direction-tuned inputs
(a) Boutons on the same axon have (b) highly correlated calcium transients. Scale bar: 5 μm. (c) Distribution of correlation coefficient R between boutons visually identified as being on the same axon (76 boutons, 24 axons). Mean: 0.81; s.d.: 0.08. Red dashed line at 0.57: 3 s.d. below the mean; Blue dashed line at 0.65: 2 s.d. below the mean. Correlation coefficients were computed over the entire imaging session. (d) Boutons in one field of view and (e) the matrix of their correlation coefficients. Scale bar: 10 μm. (f) Distribution of correlation coefficients for all fields of view (34,120 boutons, 87 fields of view). (g) Assuming boutons with R less than (upper panel) 0.65 or (lower panel) 0.57 to be from different cells, the percentage of independent boutons for each image section. Superficial image sections have more boutons from the same axons, because of the higher occurrence of horizontally elaborating axon terminals in L1.
