Subvocal activity and auditory hallucinations: clues for behavioral treatments?

Several investigators have suggested that schizophrenic patients may show an increase in subvocal speech (as measured by electromyographic [EMG] activity) during auditory hallucinations (AH), and that the subvocal activity might be antecedent to the hallucinatory experience. The possible relationship between AH and subvocal activity guided the present approach to studying behavioral interventions for AH. Duration of AH and EMG activity were recorded from 20 frequently hallucinating schizophrenic patients under baseline and experimental conditions. Three conditions were designed to interfere with activity of the speech musculature and two were imposed as controls. The data concerning the temporal relationship between EMG activity and self-report of hallucinations were inconclusive. However, one of the experimental conditions (humming a single note softly) reduced the self-report of hallucinations by 59 percent. This condition also increased EMG amplitude over baseline levels. Possible explanations for the effect of humming on hallucinations are discussed.