Sniffing out a mystery of the brain

A couple weeks ago I attended the phar­ma­ceu­tical sci­ences research expo, where, as you might imagine, a bunch of phar­ma­ceu­tical sci­en­tists got together to present their cur­rent work. Among a slew of other cool things I learned, I dis­cov­ered that we have some­thing called the Center for Trans­la­tional Neuro-​​Imaging on campus. If you want to get some little creature’s brain imaged for sci­en­tific pur­suits, Craig Ferris is your go-​​to guy at Northeastern.

Ear­lier this year Ferris put out a paper in the journal Behav­ioural Brain Research about evo­lu­tion­arily con­served olfac­tory trig­gers in rats. His team exposed awake rats to six dif­ferent smells: almond, banana, rose, citrus, peanut, and “stan­dard rat chow” (doesn’t that sound appe­tizing?) while scan­ning their little brains with func­tional MRI.

They found the results rather sur­prising. Despite never having been exposed to any kind of nut before (rat chow  con­tains no nuts), their brains lit up like Christmas trees when they smelled either peanuts or almonds and much less when they smelled the other odor­ants, which aren’t sig­nif­i­cant sources of calories.

The finding sug­gest that the ‘odorant code’ for almond extends beyond the olfac­tory bulb to include hard­wired neural net­works con­served over evo­lu­tion to rein­force adap­tive behavior crit­ical for sur­vival,” Ferris and his team write in the article. The hip­pocampus, which is crit­ical for spa­tial learning, is acti­vated upon almond sniffing, they write, sug­gesting that the neural net­work could allow rats to find food buried or hidden in the environment.

The work has impli­ca­tions for humans and our “innate” love of sweet foods, which are often high in calo­ries and seem to be deeply con­nected to emo­tional expe­ri­ences for some. It would be next to impos­sible to test the true innate­ness of our sugar love, says Ferris, because from the moment we take our first sip of milk, we are exposed to car­bo­hy­drates. This work shows that in theory a novel odor can acti­vate a neural net­work in the brain dis­tinct from the olfac­tory system without ever having learned to love it, indi­rectly sup­porting the “sweet literature.”

Anyway, it’s twenty to five and the vending machine on the first floor is faintly calling my name. I must resist.