Visual hallucinations in psychotic disorders: Clinical characteristics and the relationship with visual and auditory perception, and attention.

Ommen, M. van (Marouska) (2013) Visual hallucinations in psychotic disorders: Clinical characteristics and the relationship with visual and auditory perception, and attention. thesis, Medicine.

Text OmmenvanMM.pdf Restricted to Registered users only Download (858kB)

Abstract

Introduction: Visual hallucinations (VH) in psychotic disorders have a prevalence of 14-72%. Despite this high prevalence, little is known about its characteristics and etiological mechanism. We will explore two possible explanations for its occurrence. VH in Parkinson's Disease en Dementia seem to be explained by the Perception and Attention Deficit model, which states that dual impairments in visual perception (bottom-up processing) and attention (top-down processing) are associated with VH. This study will assess the same clinical tests as used in Parkinson's Disease, assessing these cognitive factors, so we will be able to compare results. Auditory-verbal hallucinations in psychotic disorders seem to be caused by heightened attention for auditory-verbal information and making decisions without full information, the Jumping to Conclusions bias. The question is whether this is a modality-specific effect or whether this affects multiple modalities. Research questions: What are characteristics of VH in psychotic disorders? Are there differences in the performance on tasks measuring visual and auditory perception, and attention between patients with a psychotic disorder with and without VH, and healthy controls? Methods: Six patients with schizophrenia, schizophreniform disorder or schizoaffective disorder with VH are interviewed about their VH, using 'De Visuele Hallucinatie Vragenlijst'. Also, their scores on tests assessing visual perception (Visual Object and Space Recognition (VOSP), Image Recognition Movies (IRM)), sustained attention (the subtest 'Vigilance' of the Test Battery of Attentional Performance (TAP)) and auditory perception (Speech Discrimination Task (SDT)) are compared to 7 patients with one of these psychotic disorders without VH, and healthy controls. Patients are recruited via the GROUP-study and the Department of Psychosis, UMCG. Results: VH in psychotic disorders show a wide variety in content and emotional impact. Our data confirms their bizarre, delusional and hyper-religious character. Patients with VH do not have a worse performance on tests assessing visual perception or attention (VOSP, IRM and TAP) than the other two groups. They do significantly show more 'hits' in auditory perception (SDT) compared to patients without VH, and a trend towards this is visual perception (IRM), and a lower amount of 'don't know' in both tests than both patients without VH and healthy controls. Discussion: The PAD-model does not seem to explain VH in psychoses, whereas it does is in Parkinson's Disease and Dementia. This difference could be due to different etiological mechanisms in these diseases. Also, characteristics of VH are different. The Jumping to Conclusion bias does seem to be underlying mechanism. As similar results are reported for both visual and auditory perception, this bias seem to affect both modalities. The trend towards higher prevalences of hallucinations in other modalities reported in patients with VH, as well as the fact that auditory-verbal hallucinations also have a bizarre, delusional or hyper-religious character, seem to confirm this suggestion of a common underlying mechanism. However, we must be careful with interpretations of our results, as our sample size does not meet the sample size calculation. Conclusion: Our results seem to suggest that impairments in bottom-up processing may not be related to VH in psychotic disorders. However, aberrant top-down processing does seem to play a role in the generation of VH in patients with psychotic disorders.This seems to affect multiple sensory modalities. But final conclusions cannot be drawn after inclusion of the full sample size.

Item Type:	Thesis (Thesis)
Supervisor name:	Laar, Dr. T. van
Faculty:	Medical Sciences
Date Deposited:	25 Jun 2020 11:00
Last Modified:	25 Jun 2020 11:00
URI:	https://umcg.studenttheses.ub.rug.nl/id/eprint/2060

Actions (login required)

View Item