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Nonlanguage Cognitive Deficits and Hallucinations in Schizophrenia

To the Editor: Ralph E. Hoffman, M.D., and colleagues (1) reported impaired performance of hallucinating schizophrenic patients on a narrative speech perception task and a sentence-repetition task relative to nonhallucinating patients and normal comparison subjects. However, the hallucinating and nonhallucinating patients did not differ on a measure of continuous performance, which indicated that the differences in speech perception were not due to deficits in sustained attention. Dr. Hoffman et al. concluded, "Results support the hypothesis that hallucinated voices in schizophrenia arise from disrupted speech perception and verbal working memory systems rather than from nonlanguage cognitive or attentional deficits" (p. 393). We think that the first part of the conclusion is adequate (i.e., it is supported by the data), but the latter part may be premature. Specifically, the two nonlanguage cognitive functions that have figured most prominently in the cognitive theories of hallucination—namely, reality monitoring and imagery vividness—were not assessed by the authors. Previous studies have revealed differences between hallucinating and nonhallucinating patients on tasks measuring these functions (e.g., references 2–4). Although, as Dr. Hoffman et al. pointed out, one PET study of hallucinations failed to find an activation of Broca’s area, which challenges the reality-monitoring account that hallucinations are misidentified thoughts. All studies of functional brain imaging during auditory hallucinations (e.g., reference 5) have demonstrated activation of the temporal areas, consistent with speech perception as imagery accounts (auditory imagery has been shown to activate temporal auditory association areas [6]). In addition, the speech perception tasks used by Dr. Hoffman et al. may involve mental imagery to a significant extent. The process of filling in the blanks during speech perception to reduce acoustically ambiguous speech is clearly dependent on imagery. Indeed, Kosslyn and Sussman (7) have argued that "immaculate perception" does not exist: in most circumstances, perception and imagery are intimately intertwined. This underscores the importance of a thorough investigation of the differences between patients with and without hallucinations on multiple tasks aimed at measuring language-specific (e.g., speech perception) as well as non-language-specific (e.g., reality monitoring and mental imagery) cognitive functions that may be involved in the cognitive basis of hallucinations. It is too early yet to discard the possible contribution of disruptions in nonlanguage cognitive functions to the occurrence of hallucinations in schizophrenia.

REFERENCES

1. Hoffman RE, Rapaport J, Mazure CM, Quinlan DM: Selective speech perception alterations in schizophrenic patients reporting hallucinated "voices." Am J Psychiatry 1999; 156:393–399[Abstract/Free Full Text]
2. Mintz S, Alpert M: Imagery vividness, reality testing, and schizophrenic hallucinations. J Abnorm Psychol 1972; 79:310–316[Medline]
3. Morrison AP, Haddock G: Cognitive factors in source monitoring and auditory hallucinations. Psychol Med 1997; 27:669–679[CrossRef][Medline]
4. Böcker KBE, van der Lee J, Hijman R, de Haan EHF: Perception, mental imagery and reality discrimination in hallucinating and nonhallucinating schizophrenic patients (abstract). J Int Neuropsychol Soc 1996; 2:204–205
5. Lennox BR, Park SB, Jones PB, Morris PG: Spatial and temporal mapping of neural activity associated with auditory hallucinations (letter). Lancet 1999; 353:644; erratum 354:518[CrossRef][Medline]
6. Zatorre RJ, Halpern AR, Perry DW, Meyer E, Evans AC: Hearing in the mind’s ear: a PET investigation of musical imagery and perception. J Cogn Neurosci 1996; 8:29–46
7. Kosslyn SM, Sussman L: Roles of imagery in perception: or, there is no such thing as immaculate perception, in The Cognitive Neurosciences. Edited by Gazzaniga MS. Cambridge, Mass, MIT Press, 1995, pp 1035–1041

Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Email this article to a Colleague Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to My Articles & Searches Download to citation manager Citing Articles via Google Scholar Articles by ALEMAN, A. Articles by DE HAAN, E. H.F. Search for Related Content PubMed Citation Articles by ALEMAN, A. Articles by DE HAAN, E. H.F. Schizophrenia Spectrum Disorders

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