Auditory/Verbal hallucinations, speech perception neurocircuitry, and the social deafferentation hypothesis

Abstract

Auditory/verbal hallucinations (AVHs) are comprised of spoken conversational speech seeming to arise from specific, nonself speakers. One hertz repetitive transcranial magnetic stimulation (rTMS) reduces excitability in the brain region stimulated. Studies utilizing 1-Hz rTMS delivered to the left temporoparietal cortex, a brain area critical to speech perception, have demonstrated statistically significant improvements in AVHs relative to sham simulation. A novel mechanism of AVHs is proposed whereby dramatic pre-psychotic social withdrawal prompts neuroplastic reorganization by the "social brain" to produce spurious social meaning via hallucinations of conversational speech. Preliminary evidence supporting this hypothesis includes a very high rate of social withdrawal emerging prior to the onset of frank psychosis in patients who develop schizophrenia and AVHs. Moreover, reduced AVHs elicited by temporoparietal 1-Hz rTMS are likely to reflect enhanced long-term depression. Some evidence suggests a loss of long-term depression following experimentally-induced deafferentation. Finally, abnormal cortico-cortical coupling is associated with AVHs and also is a common outcome of deafferentation. Auditory/verbal hallucinations (AVHs) of spoken speech or "voices" are reported by 60-80% of persons with schizophrenia at various times during the course of illness. AVHs are associated with high levels of distress, functional disability, and can lead to violent acts. Among patients with AVHs, these symptoms remain poorly or incompletely responsive to currently available treatments in approximately 25% of cases. For patients with AVHs who do respond to antipsychotic drugs, there is a very high likelihood that these experiences will recur in subsequent episodes. A more precise characterization of underlying pathophysiology may lead to more efficacious treatments.