Thursday, January 16, 2020

Sensory Nutrition

The Monell Center for taste and smell research sheds some light on the emerging field of Sensory Nutrition. Sure we're all human, and all made of the same stuff, and all programmed by DNA that is pretty darn similar. But we are not the same. We don't even taste or smell things the same, and much of that difference starts with our DNA.

Boy did I have a great conversation the other night about a friend of a friend who tried to fuse Mexican food into a Korean city's cuisine. Didn't work. Why? Cilantro, that's why.

Ambitious food alchemist didn't do his homework -- Asians in general tend to taste cilantro as "soap," i.e., gross. This isn't about preference, it's about genetics. For whatever reason, some of us code cilantro as soap and others as the most refreshing herb ever.

Monell researchers could have told him that. They're using big data, machine learning, and genome-wide association studies (GWAS) to understand the interface between sensory science, nutrition, and dietetics. They're ultimately trying to see if we can guide people into the right public health intervention just based on their genes.

Behavioral geneticist Danielle Reed, PhD, and olfactory neurobiologist Joel Mainland, PhD, helped to mine 400,000 reviews of 67,000 food products posted by 256,000 Amazon customers over 10 years. That's the big data part. The machine learning part analyzed words related to taste and smell, as well as other categories related to health.

Output? People today think food is too sweet. Wow. Never would have guessed that. No matter kind of food they were talking about, one percent of all reviews used the words "too sweet."

On the other side of the taste spectrum, and from a totally different study – there's a gene that helps you taste bitter, but if you have a hyped-up version, you will taste too much bitter, especially in vegetables like dark greens. Maybe even other bitter things coffee and beer will taste way different to you.

For reference (go ahead, dial up your time machine to about ten years into the future and pull up your DNA database), it's the taste gene TAS2R38. It codes for bitter-taste receptors on the tongue. And it has two variants, the AVI and PAV variants. Depending on the combination, you'll have a very different experience with certain bitter chemicals.

So the headline is that we're hardwired to like or dislike vegetables. Camouflaging bitter tastes with culinary creativity might not hurt. Just make sure to do your homework.

Monell Center, Philadelphia PA

Nov 2019, BBC News

Thursday, January 9, 2020

The Enlightened Nose-Brain

Scientific enlightenment may one day catch up with our primordial sense of olfaction, but not without some serious philosophical paradigm-shifting.

That's what people like Ann-Sophie Barwich are for. She specializes in the philosophy of smell, disentangling the hard problem of what a thing really is. What makes this problem hard is that over time, our society has become so "enlightened" by science, that we assume everything is understood, that we've got everything figured out. Maybe not re-usable rockets and bioethics, but the basics, like vision and olfaction for example, are all figured out, right?

Wrong. We assume we know how things work because of ideas that persist in society, ideologies about what things are, what they're supposed to be, and what we do with them. How about oxygen? That's a good story. We used to think air was empty, go figure!
And what is a chair? Where did they come from? How did we develop the standard dimension of seat height?

There are times when things change, for example when the majority of your society becomes overweight, and a chair means something different all of the sudden. Or there are cases when things were not really figured out in the first place. Like oxygen. Also like olfaction.

We think we know how olfaction works, for the most part. But as the idea develops, it becomes evident that we might be missing something. In fact, we might be missing a huge part. And the only way to progress might be to rethink the whole thing.

Smells, they vaporize into the air, waft into our nose, light up some neurons, and bam, a smell is born. Sounds simple enough. But once we try to investigate that experience further, it starts to fall apart. There's hundreds of receptors and each is controlled by its own gene, and each one of us has a different combination. Also, the vapors that make smells are constantly changing, hotter-colder, ripening-rottening. Also, the episodic memory network that we use as to interpret smells is wildly varied.

Codifying a universal language of olfaction is impossible, today at least. It's too complicated. But that's where philosophy comes in. Deep thinking on the very basic, the most basic assumptions can lead to paradigm-shifting insights, which can send inquiry into another direction. Thomas Kuhn's Structure of Scientific Revolutions (1962) explains this process pretty well, showing us how the Science of today is a series of revolutions in thought, vast shifts in paradigms, that re-constellate and re-crystallize thoughts, facts and ideas in new ways. These new paradigms enliven investigation, and reconsider previously less-popular pursuits.

Science philosopher Ann-Sophie Barwich is on a mission to rewrite the study of olfaction, and thereby to reform our interaction with it.

I'm reading a paper of hers, about odor objects, and about how they don't really exist in the way we think they do. She starts out with a stark and jarring statement:
"Theories of perception suffer from one fundamental flaw: they are theories of vision."
Barwich calls vision the "paradigm sense," and goes on to discuss how this vision-bias has slighted studies of smell by trying to make it fit into a sense that it has nothing to do with.

A reminder -- vision relies on immaterial waves of energy, whereas olfaction, called a "chemical sense," relies on physical contact with physical molecules.

Barwich goes on to jab at many of the commonly-held understandings that we use to construct our model of olfactory perception:
Behavioral function, not idealized stimulus representation, characterizes olfactory perception:
“Stimulus representation isn’t the primary business of olfaction. Rather, its job is solving a problem of valuation, rapidly encoding the biological salience of a stimulus and priming our multisensory representation of it to contextually appropriate action.”
Olfaction, valuation, and action: reorienting perception. Castro JB, Seeley WP. Front Psychol. 2014; 5():299. 
After establishing a criteria for perceptual objecthood, Barwich compares point-for-point why olfaction cannot be investigated through the lens of vision.

Smells are not objects to the mind, not the way visual elements of shape and color and line are objects. I interject here to add that olfactory perception require a body.

Humans are not a brain in a box. We are a brain in a body, and that body has grown with us from birth, and so our brain is integrated into this body, and relies on it (and its memories) in order to make sense out of the world.

Consider the idea of embodied cognition and Moravec's principle. Hans Moravec was a roboticist and pioneer of artificial intelligence in the 1980's. His conundrum asks why higher-order thinking is not that intensive computationally; yet running the sensorimotor suite of the limbic system requires tremendous resources.

Olfaction uses the limbic system in the same way that vision uses its visual cortex, and this makes it an entirely different animal.

Anyway, back to Barwich:
What primarily drives olfactory perception is not discrete, stable odor object formation but context-sensitive decision-making (Barwich, 2017, 2018). After all, the same chemical stimulus can occur in many different contexts, changing its causal disposition (e.g., in a mixture), as well as its meaning and value for the perceiver. It matters profoundly to the perceiver whether butyric acid is encountered as part of food (parmesan) or contaminants (vomit). The function of olfaction is to recognize changes in context and, in turn, affordance of the material stimulus (Barwich, 2018). Therefore, the same physical information of a stimulus can be grouped differently and matched against various cognitive templates. Its perceptual expression must be examined accordingly. Upon encountering olfactory information, the brain essentially has to decide on the grouping, salience, and value of olfactory input by matching this information with learned templates of odor categorization and other cues (cross-modal, verbal), all indicating the context in which a decision about the incoming olfactory information takes place.
 Processes of perceptual categorization, as decision-making, do not to require the notion of olfactory objecthood. Smell is intentional in the sense that it provides information about materials in the world. Its content, however, is not a perceptual expression of olfactory objects but of grouping sensory input into qualitative classes. How perceptual categories are formed is the real question that scientific and philosophical theories of olfaction must tackle next.
Barwich A. S. (2017). Up the nose of the beholder? Aesthetic perception in olfaction as a decision-making process. New Ideas Psychol. 47, 157–165. 10.1016/j.newideapsych.2017.03.013
Barwich A. S. (2018). “Measuring the world: towards a process model of perception” in Everything flows: Towards a processual philosophy of biology. eds. Nicholson D., Dupr√© J., editors. (Oxford: Oxford University Press; ), 337–356.
image source: zaksakata_blueredandpinkabstractartwork

A Critique of Olfactory Objects. Ann-Sophie Barwich. Front Psychol. 2019; 10: 1337. doi: 10.3389/fpsyg.2019.01337

Tuesday, January 7, 2020

The Future of Perception

Dec 2019, Ars Technica

Graphics cards, backpropagation, and big data – the ingredients for the deep learning revolution.

Our sense of smell is a great example of a deep-learning-style brain module, or to use a fashionable term, brain ensemble. The processing center of olfaction is the piriform cortex, the structure of which looks pretty similar to the pyramid diagrams of neural networks (and hence the origin of its name).

Furthermore, our olfactory system works a lot like a black box – we don't know what it's doing in there. The receptors do not code molecules one-to-one and they don't seem to correlate to perception in a meaningful or predictable way.

Our autobiographical memory, which is controlled and enriched by our olfactory perceptions, is a pretty big dataset. It holds all your personal memories, but including the physiological data as well, such as heart rate, hormone patterns, even sensorimotor data.

Now I'm not sure where the graphics cards come into the picture, something about parallel processing I guess. Olfaction uses around 400 receptors and vision uses 4 (three cones and one rod). I'm not a computer scientist, but GPU is like the opposite of CPU (in this context of neural nets) just as parallel processing would be opposite to serial processing. I’ll have to let someone else articulate that analogy.

Anyway, graphics cards, backpropagating neural networks, and big data are building the "deep" revolution, and I am waiting for the day that olfaction takes its role as the model sense for helping us understand and interact with our omnipotent artificial overlords.