This is mainly addressed to biologists, especially those who are studying sensory perception in animals and/or human beings. Also, people from other areas, such as medicine or engineering, who have turned their attention to neuroscience are welcome to contribute. I want to know how our system extracts pertinent features such as frequency selective transduction in the cochlea by the hair cells and orientation selective neurons in the brain. What other such processing is known, that perform dedicated feature extraction from the sensory inputs ?
Also, most sensory systems have a logarithmic response, rather than a linear response, which also can be considered a pre-processing of the signal.
Dear A.J.
In my Sensory Physiology class, I give an example that might be helpful here. In an array of sensory receptors A,B,C are adjacent to each other and D,E,F are adjacent to each other but separated a bit from A,B,C. Receptor cells A,B,C are each innervated by the dendrites of afferent nerve fiber 1 and receptor cells D,E,F are each innervated by the dendrites of afferent nerve fiber 2. Now afferent nerve fiber 1 also sends an inhibitory collateral to the dendrites of receptor cell D. A sensory stimulus now excites all 6 receptors. The stimulus striking receptors A,B,C will excite fiber 1; the stimulus striking receptors D,E,F will excite fiber 2. The inhibitory collateral results in an excitatory receptive field and an inhibitory neighborhood (surround) for fiber 2. This example illustrates the simplicity of generating an "ON" center and an "OFF" surround by virtue of the connectivity pattern between receptors. In this way, sensory receptors can extract specific features of the stimulus.
I hope this helps.
Peter
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