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Adaptation is a very robust feature of sensory processing: when a stimulus is displayed for a prolonged period, or repeatedly, the neural response to it will diminish. This process creates a local change in cortical sensitivity, which is behaviorally evident through worse sensory discrimination of subsequent stimuli which are similar to the adaptor stimulus, but better discrimination of dissimilar ones.

In the visual domain, there is also the concept of an afterimage. If one looks at a green patch for a long time, then a white wall will appear red. If one looks at a curved line for a long time, a straight line will appear to curve the other way. The landscape next to a waterfall will look like its traveling upwards, etc.

Does anything similar exist in the auditory domain? Can adaptation lead to illusory percepts in audition? And if not, why do you think this would be?

I'm particularly interested in the neural level of explanation, and would be very happy to hear all speculations, however far out they are.

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The most well known sensory after effect illusion in the auditory system is probably the Zwicker tone (Zwicker, 1964).

If a white noise with a half‐octave‐band suppression placed anywhere from 300 to 7000 Hz is presented at an over‐all sound‐pressure level of about 60 dB for 1 min and then switched off, a decaying, poststimulatory sound similar to a pure tone is heard for about 10 sec. The pitch of the post‐stimulatory tone corresponds to a frequency within the suppressed band.

Norena and Eggermont (2003) argue that compared to non Zwicker tone stimuli, Zwicker tone stimuli give rise to an increased firing rate and an increase in the between neuron correlation of spike trains (I think) in the primary auditory cortex.

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Auditory hallucinations happen very often and are non-pathological for most individuals. When triggered by psychosis (through excessive emotions, chemical imbalances, brain pathway failure) and do not stop they become pathological. In general things like hearing music when none is playing, hearing a ringing (outside of tinnitus) or hearing someone call your name (when no one is speaking or someone is referring to someone else) are this type of hallucination. Typically this happens when spazzed out high, experiencing some kind of cognitive dissonance, stressed, sleepy, it also thought that sensory deprivation triggers hallucinations of various types. In general the sensory deprivation hallucinations are thought to be caused by spontaneous firing of the auditory nerves.

The opposite case is also true when someone does have tinnitus the brain adapts in a way to ignore the spurious humming and detracts that sound from the interpretation of life around them.

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  • $\begingroup$ Thanks for your input! I was indeed thinking about auditory hallucinations as well. They prove that there is such a thing as an auditory percept in the absence of a stimulus. But that makes me even more curious about the absence of auditory aftereffects, whereas visual afterimages can be quite strong and clear. $\endgroup$
    – Ana
    Commented Oct 25, 2014 at 19:25
  • $\begingroup$ Maybe I should also add that my main area of interest is sensory adaptation, so that is my starting point in asking this question: why does adaptation lead to differences in perceptual aftereffects across the two modalities. $\endgroup$
    – Ana
    Commented Oct 25, 2014 at 19:26
  • $\begingroup$ @Ana ears are more complex than eyes and more prone to failures that are ignored by the brain due to the fact that ears are a mechanical constructs. the little hairs are frequently give false positives and negatives due to pressure changes and the stuff. The central auditory processing much constantly adapt to take into consideration these changes when interpreting sound. capd is common in those who have dyslexia and other problems. $\endgroup$
    – user6939
    Commented Oct 25, 2014 at 19:47

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