Lateralized differences in olfactory bulb volume relate to lateralized differences in olfactory function.

The present study aimed to investigate whether side differences in olfactory bulb (OB) volume correlate to respective differences in olfactory function. In a total of 164 healthy volunteers volumetric measures of the OBs were performed plus lateralized measurements of odor thresholds and odor discrimination. Side differences were defined as 10% difference between the left and right OB. In 39 cases volumes on the right side were larger than on the left side, whereas in 29 cases it was the other way around. Subjects with larger right-sided OB volumes were found to be more sensitive to odorous stimulation of the right as compared to the left nostril in terms of odor thresholds and odor detection; higher sensitivity of the left nostrils (decreased odor threshold) was observed in individuals with larger OB volumes on the left side. These data appear to suggest that OB volume may be partly dependent on lateralized influences on the olfactory system, reflecting its lateralized organization.