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Cancellation and correlation

Alain de Cheveigne

ENS, France


Perception has to do with predicting the future state of the world, on the basis of its current state and the actions that one might perform within it. Barlow has argued, in the same vein, that an important role of sensory relays is to factor incoming patterns into a part that is predictable from the past or from other sensory channels, and a part that reflects novelty.  The novel part is obtained by cancelling the predictable part.  In the auditory modality, cancellation is a useful mechanism to account for the perception of pitch or timbre, or the segregation of concurrent sounds.  Neural cancellation may be implemented based on neural delays and inhibitory gating.  Another popular principle is correlation, which involves neural delays and excitatory gating or coincidence counting, and a variant of that principle replaces delay by summation of signals in quadrature phase, within narrow-band channels tonotopically distributed across the auditory system.  These diverse principles can be combined into a unified model of neural signal processing at low levels of the auditory system.  I will discuss how this low-level module could be interfaced with higher-level cognitive mechanisms to perform non-trivial tasks of pattern recognition and auditory scene analysis. I will also try to highlight aspects that do not fit with this view.