The origin of Voices, a comparison between the neuroanatomy of normal speech perception and Auditory Verbal Hallucinations

Abstract

Auditory verbal hallucinations (AVHs) are experienced by the majority of patients with schizophrenia. In a considerable amount of patients this symptom is resistant to medication. Research after these often disturbing and unpleasant voices shed light on several functional brain regions that are activated during AVHs, but a complete model is still missing. This thesis reviews the current knowledge on brain regions that are activated during normal external speech perception and the regions that play a role in AVH perception. The comparison between brain activations during these two forms of speech perception sheds a light on the origin of AVHs. Many active brain regions are similar during external speech perception and AVHs. Furthermore, the emotional content of AVHs could be caused by the activation of the right tempoparietal lobe in schizophrenia patients. This right hemisphere is related to emotions and is less pronounced active during normal speech perception. The activation of Broca’s area during AVHs could implicate that the voices are created by the patients and supports the inner speech mode. Possibly, differences in wiring and connectivity between language related brain areas play a role in the experience of AVH. Research should aim to gain more knowledge on the fiber pathways between functional brain regions in order to establish a more accurate model on AVH perception.