Dogs' olfactory resting-state functional connectivity is modulated by age and brain shape.

Humans have long applied canine olfaction in various contexts. Dog olfactory brain networks have recently been mapped by anatomical measures, but functional connections remain unexplored. Also, whereas individual characteristics, including age, sex, and brain shape, are known to affect olfactory performance, their covariation with olfactory functional networks is unknown. To address these, we investigated dogs' resting-state functional connectivities between anatomically defined olfactory regions and assessed whether and how their olfactory functional network is affected by age, sex, and brain shape. Olfactory functional connectivity strength exhibited negative correlations with both age and brain shape: older dogs and those with rounder-shaped brains demonstrated lower functional connectivity, respectively, but no effect of sex was found. The results suggest that both aging and brain morphology can negatively impact a dog's sense of smell, and older dogs and dogs with rounder-shaped brains may have diminished olfactory performance.