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Topological Reorganization of Odor Representations in the Olfactory Bulb

Figure 4

Three-Dimensional Reconstruction of Activity Patterns during the Initial Phase of the Odor Response

(A) Three-dimensional patterns of TDCa signals evoked by six odors in one OB, time-averaged between 0 and 768 ms. Each plot symbol depicts the position of an individual neuron. Black dots and blue spheres represent MCs, gray dots and green spheres represent INs. Dots depict neurons with TDCa signals less than 10% of the maximum; colored spheres depict neurons with signals equal to or greater than 10% of the maximum. The size of spheres represents the magnitude of the TDCa signal between 10% and 90% of the maximum for each cell type and plot. Maxima were determined by averaging the largest 10% of TDCa signals and are reported in the lower left of each plot. Units are arbitrary; quantitative comparisons are valid between different activity patterns across the same cell type, but not between MCs and INs. Arrows indicate regions of dense activity (foci). Distance between ticks is 50 μm on all axes. Orientation is as indicated: anterior to posterior (A–P), medial to lateral (M–L), and dorsal to ventral (D–V).

(B) Average focalities of odor-evoked activity patterns across glomeruli (GL), MCs (MC), and INs (IN). Glomerular activity patterns (raw Ca2+ signal; dataset 1) were time-averaged over 2.4 s; MC and IN activity patterns (TDCa signal; datasets 1 and 2) were averaged between 0 and 768 ms. Error bars show SD. Asterisks above each bar indicate statistically significant differences between measured focalities and the focalities of randomized activity patterns. Asterisks above brackets indicate statistically significant differences between patterns across glomeruli, MCs and INs. Double asterisks (**) indicate p ≤ 0.01; triple asterisks (***) indicate p < 0.001. n.s., not significant.

Figure 4