Hyperosmia (heightened sense of smell) on amphetamines

[Burn it up]

I have experienced on a couple of occasions a heightened sense of smell while under the effects of amphetamine. I was reading about it and there are anecdotal reports of this happening with some frequency (I think Oliver Sacks was one of the first ones to write about it).

From my personal observations, the impression that I got was not that I experienced a false sense of heightened smell (as one could, for instance, with LSD and an apparent heightened sense of vision), but a real physical ability to perceive smells that I could not normally identify. Examples range from subtleties in the odour of people, a plastic after-taste in a cheap cologne, or a rancid smell inside the fridge. As far as I read, this happens because of low levels of dopamine in the olfactory bulbs (Atianjoh et al. (2008). "Amphetamine causes dopamine depletion and cell death in the mouse olfactory bulb”).

My question here is not actually regarding the mechanisms of this hyperosmia, but about the evolutionary implications. How come are we physically capable of detecting much more smells than we are actually perceiving and processing? It seems like a waste of resources. What is the evolutionary advantage of our brains filtering and ignoring these little subtleties?

Does it have to do maybe with a learning process by which we push the sense of smell to a secondary level of importance just because we don’t use it very often? Kind of like blind people do with the brain areas related to sight?

I just found this topic really interesting. If anybody has some insights, please chime in!

 

[AlphaMethylPhenyl]

Interesting topic! I think it might be simply that we have a finite amount of energy. We pay attention to our environment with our senses in the most efficient manner. Amphetamine releases huge stores of energy, so the brain might figure that we can afford energy allocation, even if it's not very efficient.

So in other words, there's a point that more energy put into the sense of smell would only yield a small increase in that sense, but putting more energy into the sense of hearing, would cause us to hear a lot better. This of course depends on the environment, and individual genetics.

I can offer an example. In regards to people who live in war-torn regions, their brain might put more energy into their sense of hearing, in the hopes of being able to hear gunshots further away, giving them more time to escape. This might come at the expense of the sense of taste, which wouldn't be as useful in this scenario. Additionally, those who have the genetic predisposition for heightened hearing might survive more often than those who don't.

I think you have the right idea.

 

[cr33py]

My guess would be vasoconstriction and lower swelling in the sinus. DO you have allergies? I experienced this effect myself on desipramine to a higher degree. Theres negligible antihistaminic effect to this even though its an old TCA.