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Christoph Teufel, Naresh Subramaniam, Veronika Dobler, Ian Goodyer, Paul Fletcher; The Role of Feedback Processes in the Emergence of Visual Hallucinations. Journal of Vision 2014;14(10):245. doi: https://doi.org/10.1167/14.10.245.
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© ARVO (1962-2015); The Authors (2016-present)
Feedback influences from higher levels of information processing onto lower levels are an important aspect of current models of visual perception. This framework has not only been useful in understanding visual perception in healthy observers; it has also been hypothesized that it can provide a unified explanation of both hallucinations and delusions in psychotic patients. Here, we report the result of three experiments that examined memory-based changes in the perception of two-tone images ('Mooney images') as a model for visual hallucinations. We tested the hypothesis that the visual system of hallucination-prone individuals relies more strongly on feedback processes. In the first experiment, (i) we quantified feedback-processes in a group of At-Risk-Mental-State (ARMS) patients and matched healthy controls. We employed a psychophysical task that measured observers' sensitivity to discriminate two-tone images of objects from control images (that lacked embedded objects) with and without prior knowledge of image content. In a second experiment, (ii) the same observers participated in an fMRI study in which the neural correlates of their subjective experience of two-tone images were assessed. Finally, in a correlational study (iii) we related performance of a larger set of healthy observers in the psychophysical task to their scores on two schizotypy scales indexing aberrant perception and a delusional style of thinking. Together, the three experiments provide evidence to suggest that vision in hallucination-prone individuals is characterised by a stronger influence of prior object knowledge on perception. We discuss potential candidate systems underlying this bias in information processing and the implications for models of schizophrenic and healthy vision.
Meeting abstract presented at VSS 2014
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