Brain Sci. 2013, 3, 642-669; doi:10.3390/brainsci3020642 OPEN ACCESS brain sciences ISSN 2076-3425 www.mdpi.com/journal/brainsci/ Review Mechanisms Underlying Auditory Hallucinations— Understanding Perception without Stimulus Derek K. Tracy1,2,* and Sukhwinder S. Shergill 1,3 1 Cognition, Schizophrenia & Imaging Laboratory, Department of Psychosis Studies, Institute of Psychiatry, King’s College London, London SE5 8AF, UK 2 Oxleas NHS Foundation Trust, Princess Royal University Hospital, Kent BR6 8NY, UK 3 National Psychosis Unit, South London and Maudsley NHS Foundation Trust, Bethlem Royal Hospital, Kent BR3 3BX, UK * Author to whom correspondence should be addressed; E-Mail:
[email protected]; Tel.: +44-20-8466-2500; Fax: +44-20-8466-2501. Received: 21 March 2013; in revised form: 7 April 2013 / Accepted: 18 April 2013 / Published: 26 April 2013 Abstract: Auditory verbal hallucinations (AVH) are a common phenomenon, occurring in the “healthy” population as well as in several mental illnesses, most notably schizophrenia. Current thinking supports a spectrum conceptualisation of AVH: several neurocognitive hypotheses of AVH have been proposed, including the “feed-forward” model of failure to provide appropriate information to somatosensory cortices so that stimuli appear unbidden, and an “aberrant memory model” implicating deficient memory processes. Neuroimaging and connectivity studies are in broad agreement with these with a general dysconnectivity between frontotemporal regions involved in language, memory and salience properties. Disappointingly many AVH remain resistant to standard treatments and persist for many years. There is a need to develop novel therapies to augment existing pharmacological and psychological therapies: transcranial magnetic stimulation has emerged as a potential treatment, though more recent clinical data has been less encouraging.