Visual hallucinations induced by Ganzflicker and Ganzfeld differ in frequency, complexity, and content
Abstract Visual hallucinations can be phenomenologically divided into those of a simple or complex nature. Both simple and complex hallucinations can occur in pathological and non-pathological states, and can also be induced experimentally by visual stimulation or deprivation—for example using a hig...
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| Format: | Article |
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Nature Portfolio
2024-01-01
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| Series: | Scientific Reports |
| Online Access: | https://doi.org/10.1038/s41598-024-52372-1 |
| _version_ | 1797274881879965696 |
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| author | Oris Shenyan Matteo Lisi John A. Greenwood Jeremy I. Skipper Tessa M. Dekker |
| author_facet | Oris Shenyan Matteo Lisi John A. Greenwood Jeremy I. Skipper Tessa M. Dekker |
| author_sort | Oris Shenyan |
| collection | DOAJ |
| description | Abstract Visual hallucinations can be phenomenologically divided into those of a simple or complex nature. Both simple and complex hallucinations can occur in pathological and non-pathological states, and can also be induced experimentally by visual stimulation or deprivation—for example using a high-frequency, eyes-open flicker (Ganzflicker) and perceptual deprivation (Ganzfeld). Here we leverage the differences in visual stimulation that these two techniques involve to investigate the role of bottom-up and top-down processes in shifting the complexity of visual hallucinations, and to assess whether these techniques involve a shared underlying hallucinatory mechanism despite their differences. For each technique, we measured the frequency and complexity of the hallucinations produced, utilising button presses, retrospective drawing, interviews, and questionnaires. For both experimental techniques, simple hallucinations were more common than complex hallucinations. Crucially, we found that Ganzflicker was more effective than Ganzfeld at eliciting simple hallucinations, while complex hallucinations remained equivalent across the two conditions. As a result, the likelihood that an experienced hallucination was complex was higher during Ganzfeld. Despite these differences, we found a correlation between the frequency and total time spent hallucinating in Ganzflicker and Ganzfeld conditions, suggesting some shared mechanisms between the two methodologies. We attribute the tendency to experience frequent simple hallucinations in both conditions to a shared low-level core hallucinatory mechanism, such as excitability of visual cortex, potentially amplified in Ganzflicker compared to Ganzfeld due to heightened bottom-up input. The tendency to experience complex hallucinations, in contrast, may be related to top-down processes less affected by visual stimulation. |
| first_indexed | 2024-03-07T15:05:30Z |
| format | Article |
| id | doaj.art-9f1cb432472641d48340ec7278f5356d |
| institution | Directory Open Access Journal |
| issn | 2045-2322 |
| language | English |
| last_indexed | 2024-03-07T15:05:30Z |
| publishDate | 2024-01-01 |
| publisher | Nature Portfolio |
| record_format | Article |
| series | Scientific Reports |
| spelling | doaj.art-9f1cb432472641d48340ec7278f5356d2024-03-05T18:55:54ZengNature PortfolioScientific Reports2045-23222024-01-0114111510.1038/s41598-024-52372-1Visual hallucinations induced by Ganzflicker and Ganzfeld differ in frequency, complexity, and contentOris Shenyan0Matteo Lisi1John A. Greenwood2Jeremy I. Skipper3Tessa M. Dekker4Experimental Psychology, Division of Psychology and Language Sciences, University College LondonDepartment of Psychology, Royal Holloway UniversityExperimental Psychology, Division of Psychology and Language Sciences, University College LondonExperimental Psychology, Division of Psychology and Language Sciences, University College LondonExperimental Psychology, Division of Psychology and Language Sciences, University College LondonAbstract Visual hallucinations can be phenomenologically divided into those of a simple or complex nature. Both simple and complex hallucinations can occur in pathological and non-pathological states, and can also be induced experimentally by visual stimulation or deprivation—for example using a high-frequency, eyes-open flicker (Ganzflicker) and perceptual deprivation (Ganzfeld). Here we leverage the differences in visual stimulation that these two techniques involve to investigate the role of bottom-up and top-down processes in shifting the complexity of visual hallucinations, and to assess whether these techniques involve a shared underlying hallucinatory mechanism despite their differences. For each technique, we measured the frequency and complexity of the hallucinations produced, utilising button presses, retrospective drawing, interviews, and questionnaires. For both experimental techniques, simple hallucinations were more common than complex hallucinations. Crucially, we found that Ganzflicker was more effective than Ganzfeld at eliciting simple hallucinations, while complex hallucinations remained equivalent across the two conditions. As a result, the likelihood that an experienced hallucination was complex was higher during Ganzfeld. Despite these differences, we found a correlation between the frequency and total time spent hallucinating in Ganzflicker and Ganzfeld conditions, suggesting some shared mechanisms between the two methodologies. We attribute the tendency to experience frequent simple hallucinations in both conditions to a shared low-level core hallucinatory mechanism, such as excitability of visual cortex, potentially amplified in Ganzflicker compared to Ganzfeld due to heightened bottom-up input. The tendency to experience complex hallucinations, in contrast, may be related to top-down processes less affected by visual stimulation.https://doi.org/10.1038/s41598-024-52372-1 |
| spellingShingle | Oris Shenyan Matteo Lisi John A. Greenwood Jeremy I. Skipper Tessa M. Dekker Visual hallucinations induced by Ganzflicker and Ganzfeld differ in frequency, complexity, and content Scientific Reports |
| title | Visual hallucinations induced by Ganzflicker and Ganzfeld differ in frequency, complexity, and content |
| title_full | Visual hallucinations induced by Ganzflicker and Ganzfeld differ in frequency, complexity, and content |
| title_fullStr | Visual hallucinations induced by Ganzflicker and Ganzfeld differ in frequency, complexity, and content |
| title_full_unstemmed | Visual hallucinations induced by Ganzflicker and Ganzfeld differ in frequency, complexity, and content |
| title_short | Visual hallucinations induced by Ganzflicker and Ganzfeld differ in frequency, complexity, and content |
| title_sort | visual hallucinations induced by ganzflicker and ganzfeld differ in frequency complexity and content |
| url | https://doi.org/10.1038/s41598-024-52372-1 |
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