Corlett, Pavlovian conditioning-induced hallucinations result from overweighting of perceptual priors. Using the rigorous experimental approach of Powers et al to these core features of schizophrenia spectrum disorders may show that aberrant predictive processing in generating auditory hallucinations is just the tip of the iceberg in this account of the pathoaetiology of these disorders.ġ.Ě. Research into the effects of psychedelic drugs, which are thought to weaken the functioning of top-down generative models ("priors"), are consistent with the proposal that predictive processing plays a role in minimal selfhood (6). For example, Seth and colleagues demonstrate how bodily aspects of the minimal self are generated by effective suppression (via top-down prediction) of interoceptive sensory signals and how this may go awry in pathological conditions. Some work examining how predictive processing may underlie minimal self-experience has already been conducted (4, 5). Indeed, hallucinations (and other psychotic symptoms) may be "end-state" expressions of this more fundamental disturbance of consciousness (3). Disturbance of this level of selfhood is associated with a variety of anomalous subjective experiences and has been found to distinguish schizophrenia spectrum disorders from other psychiatric disorders, predict the onset of schizophrenia spectrum disorders, correlate with a range of psychotic symptoms, and persist longitudinally in contrast to the fluctuating nature of overt psychotic symptoms (2). A strong candidate for the latter is disturbance of the "minimal" self, i.e., the foundational level of consciousness associated with an implicit sense of ownership and agency. An important next step would be to expand testing the predictive processing model beyond hallucinations to a wider array of psychotic symptomatology and to core features of schizophrenia spectrum disorders. Their four-group design and use of experimentally-induced hallucinations convincingly shows that these aberrant predictive processes may play a role in the onset of auditory hallucinations. doi: 10.4103/0972-6748.Powers et al's (1) important study demonstrates the role of top-down cognitive processes (i.e., implicit predictions) in shaping the incoming stream of sensory information. Clinical management of alcohol withdrawal: A systematic review. doi: 10.1007/s1194-2īhat PS, Ryali V, Srivastava K, Kumar SR, Prakash J, Singal A. Treatment of psychosis and dementia in Parkinson's disease. Auditory hallucinations in adults with hearing impairment: a large prevalence study. Linszen MMJ, van Zanten GA, Teunisse RJ, Brouwer RM, Scheltens P, Sommer IE. Hallucinations Experienced by Visually Impaired: Charles Bonnet Syndrome. Hallucinations: Clinical aspects and management. Auditory hallucinations in tinnitus patients: Emotional relationships and depression. Santos RM, Sanchez TG, Bento RF, Lucia MC. Persistent delusional theme over 13 episodes of psychotic depression. Ostergaard SD, Leadholm AK, Rothschild AJ. The treatment of hallucinations in schizophrenia spectrum disorders. Sommer IE, Slotema CW, Daskalakis ZJ, Derks EM, Blom JD, van der Gaag M. Prevalence and classification of hallucinations in multiple sensory modalities in schizophrenia spectrum disorders. Lim A, Hoek HW, Deen ML, Blom JD GROUP Investigators.
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