Abstract

The olfactory system was traditionally thought to lack a thalamic relay to mediate top-down influences from memory and attention in other perceptual modalities. Olfactory perception was therefore often described as an outlier among perceptual modalities. It was argued as a result that olfaction was a canonical example of a direct perception. In this paper we review functional and anatomical evidence which demonstrates that olfaction depends on both direct pathway connecting anterior piriform cortex to orbitofrontal cortex and an indirect thalamic circuit connecting posterior piriform cortex and orbitofrontal cortices to the olfactory system. We argue that the indirect corticothalamic circuit has the structure to potentially mediate mediates top-down influences of memory and attention in olfactory perception. This suggests that olfaction is not an outlier after all.