My Kitchen Experiment with Olfactory Attention

Many theories of attention postulate a mechanism involving the thalamus.  Roughly, the idea is that the thalamus can enhance certain sensory signals going to the cortex at the expense of others, and this is what constitutes (sensory) attention.  (The mechanism may depend in part on recurrent signals from cortex to thalamus.)

I’ve read several papers describing versions of this theory, by the likes of Francis Crick  (collected in the Baars et al 2003 anthology published by MIT Press).  None of them mention olfaction.  This is a problem because olfactory signals, unlike all other sensory signals, do not go through the thalamus.  So I wondered, can we attend selectively to one olfactory signal at the expense of others?  If no, this would support the theory that attention requires the thalamus.  If yes, this would undermine that theory.

Lacking the time to look for hard published evidence, I conducted my own little experiment, using myself and my wife as subjects.  Holding a bottle of vinegar and a pepper mill next to our nose, both of us reported that we can selectively attend to one smell over the other.  Thus, we collected prima facie evidence against thalamus-based theories of attention.

One plausible defense of thalamus-based theories would be that the olfactory bulb, which relays olfactory stimuli to the olfactory cortex, might contain a gating mechanism analogous to the one postulated to operate in the thalamus by the above-mentioned theories.  I don’t know whether there is any evidence supporting this possibility in the literature.  It might be an interesting hypothesis to pursue.  Either way, it seems that at least those attention theorists I have read might want to say something more about how they think olfactory attention works.

(Caveat: I did no comprehensive survey of the literature.  All I have read is some influential and representative papers.  For all I know, there might be plenty of published discussions of olfaction and attention mechanisms.)