Brain Advance Access originally published online on September 23, 2008
Brain 2008 131(12):3432-3442; doi:10.1093/brain/awn225
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The role of motor intention in motor awareness: an experimental study on anosognosia for hemiplegia
1King's College London, Institute of Psychiatry, 2Department of Psychology, Royal Holloway, University of London, 3Institute of Cognitive Neurosciences, University College London, London, UK, 4Institute of Work, Health and Organisations, University of Nottingham, Nottingham, UK and 5Stroke Unit, St Thomas's Hospital, London, UK
Correspondence to: Dr A. Fotopoulou, Centre for Neuroimaging Sciences, Box 089, Institute of Psychiatry, De Crespigny Park, London SE5 8AF, UK E-mail: a.fotopoulou{at}iop.kcl.ac.uk
Recent theories propose that anosognosia for hemiplegia (AHP) results from specific impairments in motor planning. However, no study has hitherto directly investigated the role of motor intention in the observed non-veridical awareness of action in AHP. We developed the following paradigm to investigate the role of motor planning in awareness in patients with AHP: Four hemiplegic patients with and four without anosognosia were provided with false visual feedback of movement in their left paralysed arm through a prosthetic rubber hand. We examined whether the ability to detect presence or absence of movement based on visual evidence varied according to whether the patient had planned to move their limb or not. Motor intention had a selective effect on patients with AHP; they were more likely than controls (U = 16, P < 0.001) to ignore the visual feedback of a motionless hand and claim that they moved it when they had the intention to do so (self-generated movement) than when they expected an experimenter to move their own hand (externally generated movement), or there was no expectation of movement. By contrast, patients without AHP were not influenced by these manipulations, and did not claim they moved their hand when the hand remained still. This is the first direct demonstration that altered awareness of action in AHP reflects a dominance of motor intention prior to action over sensory information about the actual effects of movement.
Key Words: anosognosia; right hemisphere; awareness; action awareness; parietal
Abbreviations: AHP, anosognosia for hemiplegia; BIT, Behavioural Inattention Test; HP, hemiplegia; HADS, Hospital Anxiety and Depression Scale; WTAR, Wechsler Test of Adult Reading
Received May 21, 2008. Revised July 13, 2008. Accepted August 22, 2008.
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