How can we or flies tell thousands of tastes or smells, considering that flies have only hundreds of neurons?
The olfactory system employs a 'combination' strategy: each olfactory neuron has only one single type of receptor which is sensitive to chemicals. There are several decades of receptor types, that is decades of neuron types. Each neuron can be activated by multiple chemicals and each chemical can activate multiple types of neurons.The result is, odorant A can activate neurons #1, 5 and 9, and #1 neuron can be responsive to odorant A, B and E. Similarly, neuron #5 can be activated by odorants C, F and H.
This kind of combination can make a matrix with thousands of different combinations, which enables flies to sense as many odorants as necessary: If #1, 3 and 5 neurons are activated by this odorant, it will be sugar. If #1, 4 and 9 neurons are responding to this odorant, it will be bitter.
No comments:
Post a Comment