Gustatory map revealed, and that's all?

 In brain connectivity, consciousness, modularity, neuroaesthetics, neuroscience

A recent news item tells us about a report that the gustatory system in mammals has been shown to have a “gustatory map”. Just in the same way that we already know that our visual and sensory-motor systems show nice and almost 1:1 mapping between sense and it’s neural representation.

It is groundbreaking work, as attested by the Science publications itself. It demonstrates clearly that even our taste system has a clear and distinct representation of different tastes. It could just as well be opposite. Taste could have been represented as different network configurations within basically the same network.

What strikes me most is the claim stated by Nicholas Ryba of the National Institute of Dental and Craniofacial Research, who was coauthor on the new study. He states in an interview:

“What is a taste, really? It’s the firing of a set of neurons in the brain, and that’s what we want to understand.”

I guess many researchers in psychology will see the shortcoming of this statement. It is a simplified claim of brain-mind relationships, and a reductionism one should handle with care. One clear shortcoming of this study is that it focuses on studying the organism – rats – from a systems neuroscience approach, paying no heed to the role of experience.

As any researcher of the mind knows, there is an explanatory gap between knowing how the brain works and to what extent any of the processes uncovered relate to overt sensory experience. Put differently, although our early visual system is neatly organised according to the visual space, this is not reflected in our experience of the world. We do not experience the world as spatially distributed pixels on a sheet. Rather, we experience the world around us as objects, context, movement etc.

Similarly, taste experience still needs to be explained. I am not sure that Ryba’s claim should be taken literary, but it reflects a notion seen every so often in the interpretation of neurobiology.

One pertinent next question, and a low hanging fruit, is to couple this to studies of preference and liking. In several studies one finds that contextual information can lead to alteration in people’s experience of a product. This includes coca-cola, wine and even art. Recently, a study suggested that subjects’ taste experiences were directly influenced by information: if told  that a ber contained drops of lemon, subjects would often report sensing the whiff of lemon.

The obvious question is now: at what level can one detect this change in taste? Here, at least two possibilities are available. On the one hand, it is possible that attentional mechanisms increase the effect of one particular sensation, e.g. sourness. On the other hand, it might be that these changes only at a higher representational level. Nevertheless, the current results provide hints pf new ways to study such effects, and to increase the likelihood that we may learn more about sensation, our pleasure of this, and how contextual cues can affect our experiences.

Thus, the recent finding of a gustatory map provides wonderful clues to the basic mechanisms of taste, but we still need to explain why the coffee I’m now drinking has such a distinct taste to me.

-Thomas

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