Vocalisation in verbal hallucinations: case report and theoretical model.

Perception of one's speech or the speech of others reflects an intrinsic process and should not to be seen as a product of information processing of external sensory input. From this perspective, the perception of one's own or others' speech is fundamentally equivalent to the experience of verbal hallucinations. Speech perception is generated primarily in the focus of attention, but auditory and proprioreceptive input from verbal articulations play an important constraining role, ensuring that perception remains adaptive to interaction with the external world. In verbal hallucinations these constraints may be partially disrupted. Perceptual qualities of hallucinatory voices may be generated in the focus of attention alone (in ignorance of actual acoustic stimulation from the environment), whilst content and grammatical aspects of hallucinatory speech perception may continue to be constrained adequately by proprioreceptive reafferentation from the speech apparatus. Thus subvocal speech may play a role in the elaboration and maintenance of verbal hallucinations.