Olfactory coding

Preparation

  • Read the Introduction and Psychological Questions (two pages: p. 217-218) of Speculations on Smell [PDF] (written 60 years ago by Jerome Y. Lettvin and Robert C. Gesteland). Consider the quality of the writing and the character of this “phenomenological” analysis of the lived experience of smell.
  • Read the first half of Chapter 2 “Olfaction” (pp. 37-45) in The Neuroethology of Predation and Escape by Keith T. Sillar, Laurence D. Picton, William J. Heitler (Wiley-Blackwell, 2016). [SWEM Online] [PDF]

Speculations on Smell by Lettvin and Gesteland (1965)

How we smell is as hard to dissect as how we see.  A recent may smell like lavender, a stink may smell like rotten eggs — but the figure of speech is as far as we can go.  … Most odors are complex; we scent them as singular forms.  There is the smell of home, the reek of fever, the stench of fear, the good odor in which saintly people die.  … [G]iven sufficient training, some of us can say if a vintage had seen the sea.  But there is no way of telling these perceptions to others except by simile.  Even when professional perfumers address each other, it is in a cant that evokes intuition rather than understanding. There are “floral top-notes” and “spicy undertones” modifying a “fragrance theme,” … and these are professionals trying to communicate, not art critics trying to confuse each other.

…[T]he function of smell is not to tell pure chemicals apart but to distinguish clearly between very similar mixtures.

Lettvin, J.Y. and Gesteland, R.C., 1965. Speculations on smell. In Cold Spring Harbor Symposia on Quantitative Biology (Vol. 30, pp. 217-225). Cold Spring Harbor Laboratory Press.  The assigned reading is pp. 217-218, but there is an interesting discussion of olfactory coding that begins on p. 223.

Cori Bargmann – Cracking the olfactory code

Further reading

Ache, B.W., Hein, A.M., Bobkov, Y.V. and Principe, J.C., 2016. Smelling time: A neural basis for olfactory scene analysis. Trends in neurosciences, 39(10), pp.649-655.

Bushdid, C., Magnasco, M.O., Vosshall, L.B. and Keller, A., 2014. Humans can discriminate more than 1 trillion olfactory stimuli. Science, 343(6177), pp.1370-1372.[PDF]

Firestein, S., 2005. A Nobel nose: the 2004 Nobel Prize in Physiology and Medicine. Neuron, 45(3), pp.333-338.   [PDF]

Howard, J.D., Plailly, J., Grueschow, M., Haynes, J.D. and Gottfried, J.A., 2009. Odor quality coding and categorization in human posterior piriform cortex. Nature Neuroscience, 12(7), p.932.  [PDF]

Isaacson, J.S., 2010. Odor representations in mammalian cortical circuits. Current opinion in neurobiology, 20(3), pp.328-331

Laurent, G., 1996. Dynamical representation of odors by oscillating and evolving neural assemblies. Trends in neurosciences, 19(11), pp.489-496.

Lettvin, J.Y. and Gesteland, R.C., 1965, January. Speculations on smell. In Cold Spring Harbor Symposia on Quantitative Biology (Vol. 30, pp. 217-225). Cold Spring Harbor Laboratory Press.

Malnic, B., Hirono, J., Sato, T. and Buck, L.B., 1999. Combinatorial receptor codes for odors. Cell, 96(5), pp.713-723.[PDF]

Poo, C. and Isaacson, J.S., 2009. Odor representations in olfactory cortex: “sparse” coding, global inhibition, and oscillations. Neuron, 62(6), pp.850-861.