Testing the PAD model using priming of ambiguous visual stimuli
Research type
Research Study
Full title
Testing the Perception Attention Deficit (PAD) model of complex visual hallucinations using conceptual priming of ambiguous visual objects
IRAS ID
144270
Contact name
C Colbourn
Contact email
Sponsor organisation
Tees, Esk and Wear Valleys NHS Foundation Trust
Duration of Study in the UK
0 years, 7 months, 0 days
Research summary
Visual hallucinations (VH) can broadly be defined as seeing something that others do not. This experience can be distressing and is associated with poorer health outcomes. Lewy body diseases (LBD) are a collection of conditions characterised by a high prevalence of VH. People with LBD show impairments in attention and visual perception. Attention can be conceptualised as a "top-down" process, and perception as a "bottom-up" process. It has been proposed that visual hallucinations occur because of an impaired interaction between these these processes (Collerton, Perry & McKeith, 2005). In other words, visual hallucinations are the product of the breakdown of the interaction between visual perception, and attention. The proposed study aims to test this theoretical model by using an experimental task that requires both attention and perception. Priming refers to the effect of a previously seen item on the response to another. For example, a person who is asked if “rabbit” is a word will respond more quickly and more accurately if this word was preceded by the word “carrot”. Priming has an effect on a person’s attention. Ambiguous images (e.g. pictures that are visually degraded, or objects that have more than one interpretation) are analogous to visual impairments, as what is seen cannot be determined by visual information alone. Therefore, combining these two phenomena (i.e. priming of visually ambiguous images) offers a way to experimentally test attention and perception simultaneously. The current study proposes to compare hallucinating patients with LBD, with non-hallucinating patients with LBD, on a priming test of visually ambiguous objects. Because people with LBD who hallucinate are believed to have an impairment in the interaction between perception and attention, it is predicted that this group of patients will display characteristically different performance on the tests in comparison to non-hallucinating patients.
REC name
North East - Tyne & Wear South Research Ethics Committee
REC reference
14/NE/1104
Date of REC Opinion
27 Oct 2014
REC opinion
Further Information Favourable Opinion