[Auditory hallucinations and functional imaging].

Auditory verbal hallucinations are a common symptom of schizophrenia. In general, hallucinations can affect all sensory modalities and occur in many neuropsychiatric disorders. They also serve the psychology of perception as the classic example of sensory experience in the absence of adequate external stimuli. Functional imaging studies showed the auditory cortex, the limbic system and language areas, both motor and sensory, to be active during auditory hallucinations. The psychological and neurophysiological models of hallucination can be integrated if we consider that patients with schizophrenia might ascribe internal monologues or dialogues to external sources. The activity of language areas during hallucinations would conform to such a model while the activity in auditory cortex might explain why auditory hallucinations are often so vivid and real for the patients suffering from them. Moreover, the activation of the limbic system might correspond to the emotional aspects of the content of the voices and the accompanying arousal. While the neurophysiological models of hallucination are thus already rather refined, the attempt at suppressing auditory cortex activity with repetitive transcranial magnetic stimulation in order to alleviate treatment-resistant acoustic hallucinations, which is based on the functional imaging findings, still needs further study. Treatment schemes that are based on the psychological theories are more varied and have shown more consistent and long lasting effects but also suffer from the difficulty in measuring hallucinations quantitatively. Future research with functional and structural imaging should go beyond correlating brain activity and symptoms and also address the functional and structural connectivity patterns in the brain that enable hallucinations.