Feedback in outer haircells enhances sensitivity while lateral spread shapes frequency selectivity.

Evidence

An important part of this functional scheme is the fact that the output of the outer haircells can influence their input. Such feedback systems are very sensitive, and they have the tendency to be self-oscillating. Close to self-oscillation, the feedback loop, with appropriate phase characteristics, enhances the adequate stimulus for the outer haircells considerably. If there were no lateral spread of the feedback, this would lead to an extremely selective frequency response. Lateral spread of the feedback produces a band-pass-like frequency selectivity but still preserves the very high sensitivity as discussed 3. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 242

Categorization

• DEEPTHINKING: The insight that a self-oscillation-prone feedback loop underlies the ear’s extraordinary sensitivity — amplification bought by operating on the edge of instability — is a genuinely deep and counterintuitive systems idea.
• XREF: Connects to the general principle of ‘criticality’/‘edge of chaos’ in biological systems (e.g. neural avalanches, self-organized criticality).