Fig. 3.

Measurements of interbulbar symmetry.A, Degree of symmetry for individual odorant representations were determined from bilateral image overlap (Fig. 2); percentage overlap was calculated and averaged for each odorant. The overlap value ranged from 14 to 25% for propanal to hexanal, respectively. These values, although lower than expected for perfect symmetry, are nonetheless significantly greater than overlap between different odors, such as propanal and hexanal (Student'st test, p < 0.001).B, Average symmetry of the centroid of activation by different odorants, derived from the x(black) and y (white) values of the left and right bulb centroids (see Materials and Methods). The average centers of activity are much more symmetric than the precise overlap of glomeruli as determined in A.C, Symmetry of related odorants determined by comparing the averaged x and y centroid ratios of odorant maps elicited by the same odorant (0C) as inB, and odorants differing by one to three carbons (1C, 2C, 3C). Linear regression of x (▪,R² = 0.6443) andy (■, R² = 0.9045) values demonstrates that increasing carbon chain length results in significantly greater change in the anterior–posterior axis (y) than in the medial–lateral axis (x).