title: Imagine that: elevated sensory strength of mental imagery in individuals with Parkinson's disease and visual hallucinations.
abstract: Visual hallucinations occur when our conscious experience does not accurately reflect external reality. However, these dissociations also regularly occur when we imagine the world around us in the absence of visual stimulation. We used two novel behavioural paradigms to objectively measure visual hallucinations and voluntary mental imagery in 19 individuals with Parkinson's disease (ten with visual hallucinations; nine without) and ten healthy, age-matched controls. We then used this behavioural overlap to interrogate the connectivity both within and between the major attentional control networks using resting-state functional magnetic resonance imaging. Patients with visual hallucinations had elevated mental imagery strength compared with patients without hallucinations and controls. Specifically, the sensory strength of imagery predicted the frequency of visual hallucinations. Together, hallucinations and mental imagery predicted multiple abnormalities in functional connectivity both within and between the attentional control networks, as measured with resting-state functional magnetic resonance imaging. However, the two phenomena were also dissociable at the neural level, with both mental imagery and visual misperceptions associated with specific abnormalities in attentional network connectivity. Our results provide the first evidence of both the shared and unique neural correlates of these two similar, yet distinct phenomena.
authors.affiliation: Brain and Mind Research Institute, The University of Sydney, Sydney, New South Wales, Australia mac.shine@sydney.edu.au.
authors.forename: James M
authors.initials: JM
authors.lastname: Shine
authors.affiliation: School of Psychology, University of NSW, Sydney, New South Wales, Australia.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Keogh
authors.affiliation: Brain and Mind Research Institute, The University of Sydney, Sydney, New South Wales, Australia Neuroscience Research Australia, University of NSW, Sydney, New South Wales, Australia.
authors.forename: Claire
authors.initials: C
authors.lastname: O'Callaghan
authors.affiliation: Brain and Mind Research Institute, The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Alana J
authors.initials: AJ
authors.lastname: Muller
authors.affiliation: Brain and Mind Research Institute, The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Simon J G
authors.initials: SJ
authors.lastname: Lewis
authors.affiliation: School of Psychology, University of NSW, Sydney, New South Wales, Australia.
authors.forename: Joel
authors.initials: J
authors.lastname: Pearson
mesh_terms: D000368:Aged; D001288:Attention; D001931:Brain Mapping; D005260:Female; D006212:Hallucinations / Q000503:physiopathology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000503:physiopathology*; D014796:Visual Perception
keywords: attentional networks; bistable perception; mental imagery; resting-state functional connectivity; visual hallucinations