auditory hallucination

   Also known as acoustic hallucination, aural hallucination, and hallucination of hearing. Auditory hallucinations are the most prevalent type of hallucinations in adults with or without a history of psychiatric illness. It is estimated that the 1-year prevalence of auditory hallucinations in the general, non-institutionalized population lies between 2 and 3%. In schoolchildren the 1-year prevalence of auditory hallucinations has been found to be no less than 9%. The lifetime prevalence of auditory hallucinations in the non-institutionalized population has been reported to be at least 70%. In individuals with a clinical diagnosis of "dissociative disorder, the lifetime prevalence of auditory hallucinations is estimated at around 85%. In individuals with a clinical diagnosis of " schizophrenia, this rate is 60-70%. In comparison with the group of non-institutionalized individuals, the latter two groups are characterized by a markedly higher mean frequency of hallucinations, as well as a higher prevalence of negative attribution and/or content. Auditory hallucinations are experienced as coming from inside or outside the head and are therefore referred to as " internal or " external auditory hallucinations. External auditory hallucinations can be experienced as coming from a fixed location and/or distance in extracorporeal space, but often their apparent source is indeterminable. The perception of auditory hallucinations tends to be independent of the individual's own location. However, some individuals claim that their auditory hallucinations are sometimes 'left behind' when they move from one spot to another. For example, a voice heard in the kitchen while cooking a meal is later heard as if coming from the kitchen, even after everyone is seated at the table in an adjacent room. The frequency and intensity of auditory hallucinations may vary in accordance with such factors as the increase or decrease in the intensity of background noises, the presence or absence of certain individuals, the presence or absence of psychosocial stresses, the individual's senso-rium, and the prior use of therapeutics, alcohol, or other substances. When auditory hallucinations are prompted by a regular sense perception in one of the other sensory modalities, they are referred to as " synaesthesias. " Light-phonisms, for example, constitute a subgroup of the synaes-thesias characterized by an auditory hallucination prompted by a regular visual percept. When such regular percepts are lacking and auditory hallucinations are described as "being heard by" another body part than the ears (i.e. by the eyes, or the knee, or the stomach), they are referred to as " extracampine hallucinations. When they occur simultaneously with a hallucination in one or more of the other sensory modalities, they are classified as compound hallucinations. In accordance with varying guiding principles and goals, auditory hallucinations can be divided into various subtypes. Thus the German neurologist Carl Wernicke (1848-1904) divides auditory hallucinations into " verbal auditory hallucinations (which he calls "phonemes) and "nonverbal auditory hallucinations (or "akoasms). Verbal auditory hallucinations (VAHs) have also been termed " auditory verbal hallucinations (AVHs). Patho-physiologically, VAHs are associated with aberrant neurophysiological activity in the left temporal lobe, more specifically, in the gyrus temporalis superior, Heschl's gyrus, the planum temporale, and the speech areas (i.e. Broca's area and Wernicke's area). Functional MRI findings suggest that the right homologue of Broca's area may be involved in the mediation of VAH as well. Moreover, it has been hypothesized that the cortical hallucinatory activity characteristic of VAH may be preceded by subcortical activity, notably from within the limbic system and amygdala. Theoretically, this makes sense if the hallucinations at hand are interpreted as " reperceptions of previously memorized speech. Neuroimaging findings would seem to suggest that, in some cases at least, alterations of white matter fibre tracts connecting areas relevant to speech perception and/or production may also be responsible for the mediation of VAHs. VAHs occurring simultaneously with subtle instances of motor activity within the larynx and/or the vocal cords are covered by the term " subvocalization. In the older literature this phenomenon is also referred to as " motor verbal hallucination, " psychomotor verbal hallucination, and " muscular verbal hallucination. VAHs that repeat or echo the subject's conscious thoughts are referred to in the literature as " Gedankenlautwerden, thoughts-out-loud, audible thinking, and écho de la pensée.When VAHs come in the form of an incentive or command, they are referred to as " command hallucinations or " imperative hallucinations. Nonverbal (or " nonvocal) auditory hallucinations come in many forms. When they appear in the form of music, they are referred to as " musical hallucinations. Amorphous and often continuous sounds such as buzzing, humming, the sound of running water, or waves upon the shore have traditionally been interpreted as signs of "tinnitus. However, the more recent literature suggests that there is considerable overlap - conceptually as well as phenomenologically and perhaps also physiologically - between tinnitus and auditory hallucinations. Theoretically, nonverbal auditory hallucinations can be mediated by any part of the auditory system, ranging from the cochlea and acoustic nerve to the primary auditory cortex and association cortex. Where they have a demonstrable relation to structural and/or functional abnormalities in the brainstem, they are referred to as " brainstem auditory hallucinations. The traditional explanatory models for the mediation of auditory hallucinations include the " reperception model, the " perceptual release model, the "dissociation model, and the "inner speech model.

   References

   Wernicke, C. (1900). Grundriss der Psychiatrie. Leipzig: Verlag von Georg Thieme.

   Dierks, T., Linden, D.E., Jandl, M., Formisano, E., Goebel, R., Lanfermann, H., Singer, W. (1999). Activation of Heschl's gyrus during auditory hallucinations. Neuron, 22, 615-621.

   Leudar, I., Thomas, P. (2000). Voices of reason, voices of insanity. Studies of verbal hallucinations. London: Routledge.

   Van der Gaag, M., Hageman, M.C., Birchwood, M. (2003). Evidence for a cognitive model of auditory hallucinations. Journal of Nervous and Mental Disease, 191, 542-545.

   Sommer, I.E.C., Aleman, A., Kahn, R.S. (2003).

   Left with the voices or hearing right? Later-alization of auditory verbal hallucinations in schizophrenia. Journal of Psychiatry and Neuroscience, 28, 17-18.

   Hayashi, N., Igarashi, Y., Suda, K., Nakagawa, S. (2004). Phenomenological features of auditory hallucinations and their symptomatolog-ical relevance. Psychiatry and Clinical Neurosciences, 58, 651-659.

   Hunter, M.D. (2004). Locating voices in space: A perceptual model for auditory hallucinations? Cognitive Neuropsychiatry, 9(1/2), 93-105.

   Hanssen, M., Bak, M., Bijl, R., Vollebergh, W., van Os, J. (2005). The incidence and outcome of subclinical psychotic experiences in the general population. British Journal of Clinical Psychology, 44(Pt2), 181-191. Blom, J.D., Sommer, I.E.C. (2009). Auditory hallucinations. Cognitive and Behavioral Neurology (in press).