It is relatively common to experience auditory hallucinations following hearing loss. It has been suggested that these hallucinations are the result of a ‘release’ of inhibition, normally provided by auditory experience. This inhibition would act to balance the reciprocal activity between high- and low-level processing centers, which both transfer basic sensory information, as well as “fill in the gaps” to provide a cohesive auditory experience. When the former high-level centers are in overdrive, however, the effect may be to trigger complex auditory percepts, without a driving auditory stimulus.
Oliver Sacks describes this phenomenon, along with an (as usual) gorgeously written account of the “Power of music” in the journal Brain (Sacks, 2006 - free!), an excerpt of which is included below. An interesting aspect of the above hypothesis is that we may expect these hallucinations to disappear if afferent drive (auditory input) is restored, for instance, via a cochlear implant. This does not appear to be the case. This is described in more detail by Sacks in this NPR Story, and in his recent book, Musicophilia.
Our auditory systems, our nervous systems, are tuned for music. Perhaps we are a musical species no less than a linguistic one. But there seems to be in us a peculiar sensitivity to music, a sensitivity that can all too easily slip out of control, become excessive, become a susceptibility or a vulnerability. Too-muchness lies continually in wait, whether this takes the form of ‘earworms’, musical hallucinations, swoons and trances, or music-induced seizures. This is the other side of the otherwise wonderful power of music. How much this is due to the intrinsic characteristics of music itself—its complex sonic patterns woven in time, its logic, its momentum, its unbreakable sequences, its insistent rhythms and repetitions, the mysterious way in which it embodies emotion and ‘will’—and how much to special resonances, synchronizations, oscillations, mutual excitations, feedbacks, and so forth, in the immensely complex, multi-level neural circuitry that subserves musical perception and replay, we do not know. We do not even know why, for instance, simple stroboscopic light displays can excite hallucinations, myoclonus and seizures, and this is an infinitely simpler matter than the powers of music.
When Crichtley and Henson’s Music and the Brain was published in 1977, functional brain imaging still lay in the future, and neuroscience had yet to approach the neural correlates of musical perception, imagery and memory or their disorders. In the last 20 years, there have been huge advances here, but we have, as yet, scarcely touched the question of why music, for better or worse, has so much power. It is a question that goes to the heart of being human.
