Fig. 2.
Analysis of functional glomerular heterogeneity in OMP–/– glomeruli. a Raw two-photon fluorescence of a glomerulus in an OMP–/– mouse. b, c Example time courses and average responses (dF/F) of the glomerulus in (a) to 4 different stimuli. Colored circles mark regions of interest and correspond to color of traces in (b). Green horizontal line marks stimulus delivery. d (Top) Projection of all pixels in (a) on two principal components (PC1 vs. PC2) reference coordinates. PCA was performed on the odor response spectra of each pixel. (Bottom) Average odor response spectra of three functional clustered identified in glomeruli from (a). Color scale units are correlation coefficients. e Spatial correlograms showing the spatial distribution of the three pixel clusters identified via PCA in (d) within the example glomerulus (a) were obtained by correlating the average response vectors of the identified clusters to the odor responses of individual pixels in the field of view. Numbers mark correlation maps corresponding to each functional cluster in (d). Note that each cluster corresponds to a spatially contiguous area we refer to as a microdomain. f (Left) Cartoon depicting two optical imaging planes (z) within the example glomerulus (a) at two different depths (I and II, 20 µm apart). (Center and Right) RGB color scheme overlays of the correlograms determined as in (e) for the two optical planes sampled within the glomerulus. Blue corresponds to image 1 in (e), green to image 2, red to image 3. g Three spatial microdomains in a second example glomerulus in the OMP–/– mouse. (Left) Average odor response spectra of functional clusters identified via PCA. (Right) Resting fluorescence, single pixel correlograms, and their overlay in an RGB scheme. Color scale units are correlation coefficient. h Summary graph of the average frequency of glomerular heterogeneity recorded in OMP+/– and OMP–/– mice (4.8 ± 2.5%, n = 4 bulbs versus 24.7 ± 6.9%, n = 7 bulbs, p = 0.0058, Mann–Whitney U test; horizontal bars represent the mean, dots individual animals). i Histogram of pairwise odor response similarity between functional domains within the same anatomical glomerulus (red) and between different glomeruli (black) in OMP–/– mice. Results are presented as means ± SEM; **p < 0.001; scale bar, 20 μm