Naked Science Forum
Life Sciences => Physiology & Medicine => Topic started by: thedoc on 26/11/2012 16:52:25
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Just as you can see white light, and hear white noise, it seems we are also susceptible to a white smell – or “olfactory white”...
Read the whole story on our website by clicking here (http://www.thenakedscientists.com/HTML/content/news-archive/news/1000022/)
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We selected 86 molecules that span olfactory stimulus space and individually diluted them to a point of about equal intensity...
We obtained 86 monomolecular odorants that were well distributed in both perceptual (Fig. 1A) (1, 11–13) and physicochemical (Fig. 1B) (1, 14, 15) stimulus space.
Fig. 1A shows a 2D graph with axes "PC1" and "PC2".
Can anyone with some knowledge of olfactory research explain the "perceptual space" for smells. It's something which I've never seen referred-to before, and it intrigues me.
I have a purely personal "graphical" visualisation of smells which is a simply a 1D representation (though I'd be hard-pressed to place anything on a specific part of the axis) - I mostly visualise smells as "spiky" where there's some one or more kinds of dominant sharp component, or "broad" which gives a smell more "body" rather than being "thin" (which it would be if there were nothing between the spikes). Does this make any sense to anyone?
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In vision and audition, the clear mapping between physical and perceptual dimensions allowed identification of the physical limits of perception (390 to 750 nm in color vision and 20 Hz to 20 kHz in auditory pitch). Therefore, spanning physical space in these domains is relatively straightforward. In contrast, the full extent of olfactory physicochemical space remains unknown, and its key axes remain poorly defined.
Seems we need some more research in this field!
I postulate that the human nose and sensory system has more in common with the ear than with colour-perception - a fair greater number of "channels" and hence required "aromatic primaries" to reproduce an arbitrary smell.
For colour, you only need three primaries (X,Y,Z or loosely red/green/blue) to simulate an arbitrary colour.
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There are after-images (https://en.wikipedia.org/wiki/Afterimage), are there after-smells ?
https://en.wikipedia.org/wiki/Olfactory_adaptation
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There are after-sounds too... some forms of tinnitus!
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There are definitely after smells. I used to smoke and two or three paces past a smoker on the street I get a distinctive smell/urge; its not the smoke directly, and I don't get it in a room with a smoker. I think its the chemicals of smoke rarefied and purified on the breeze and my body realizing what it just smelled and that it could quite go for it! About ten years now and counting - so not a problem, but it is the only time I am tempted and sober.