What is it about?

Auditory verbal hallucinations (AVHs) are speech perceptions in the absence of external stimulation. According to an influential theoretical account of AVHs in schizophrenia, a deficit in inner-speech monitoring may cause the patients’ verbal thoughts to be perceived as external voices. We have examined lip muscle activity during AVHs in patients with schizophrenia to check whether inner speech occurred. We have found subtle lip muscle activity during auditory verbal hallucinations. These results are in favor of the hypothesis that AVHs might be self-generated inner speech.

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Why is it important?

Our findings show that auditory verbal hallucinations (AVHs) are accompanied with subtle lip muscle activity. This provides empirical arguments in favor of the view that AVHs might be self-generated inner speech that is mis-monitored. It is a strong argument for a motor origin of AVHs. We discuss these results in the framework of the predictive control model of speech production (or comparator model). We suggest amendments to the model that make it more applicable to inner speech and more susceptible to explain AVHs.

Perspectives

These findings point to the motor origin of AVHs, which are then interpreted as sensory (auditory) percepts. We question the predictive control (or comparator model) in several of its assumptions and provide amendments. Further studies should investigate how different voices may be heard by patients. If AVHs stem from inner speech production, and correspond to the output of an internal model, then further studies should examine whether different internal models are used for different voices, and how these internal productions are monitored. Further accounts of AVHs should also include factors such as attention, intentionality, externalization bias, and metacognitive beliefs.

Dr Helene Loevenbruck
CNRS UMR 5105 - Université Grenoble Alpes

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This page is a summary of: An EMG Study of the Lip Muscles During Covert Auditory Verbal Hallucinations in Schizophrenia, Journal of Speech Language and Hearing Research, December 2013, American Speech-Language-Hearing Association (ASHA), DOI: 10.1044/1092-4388(2013/12-0210).
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