Brain Advance Access originally published online on December 22, 2003
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Brain, Vol. 127, No. 2, 431-438, 2004
© 2004 Guarantors of Brain
doi: 10.1093/brain/awh051
Visual exploration behaviour during clock reading in Alzheimer’s disease
,1
1 Perception and Eye Movement Laboratory, Departments of Neurology and Clinical Research, University of Bern and
2 Memory Clinics, Departments of Neurology and Psychiatry, University of Bern, Switzerland
*Present address: Institute for Ageing and Health, Wolfson Research Centre, Newcastle General Hospital, Newcastle, UK
Present address: Department of Radiology, University Hospital of Nancy, Nancy, France
Correspondence to: PD Dr R. M. Müri, Perception and Eye Movement Laboratory, Departments of Neurology and Clinical Research, University of Bern, Inselspital, 3010 Bern, Switzerland E-mail: rene.mueri{at}insel.ch
Eye movement behaviour during visual exploration of 24 patients with probable Alzheimer’s disease and 24 age-matched controls was compared in a clock reading task. Controls were found to focus exploration on distinct areas at the end of each clock hand. The sum of these two areas of highest fixation density was defined as the informative region of interest (ROI). In Alzheimer’s disease patients, visual exploration was less focused, with fewer fixations inside the ROI, and the time until the first fixation was inside the ROI was significantly delayed. Changes of fixation distribution correlated significantly with the ability to read the clock correctly, but did not correlate with dementia severity. In Alzheimer’s disease patients, fixations were longer and saccade amplitudes were smaller. The altered visual exploration in Alzheimer’s disease might be related to parietal dysfunction or to an imbalance between a degraded occipito-parietal and relatively preserved occipito-temporal visual network.
Key Words: Alzheimer’s disease; clock reading; visual exploration
Abbreviations: CFP = central fixation point; ChE-I = cholinesterase inhibitors; DSM-IV= Diagnostic and Statistical Manual of Mental Disorders (4th edition); MMSE = Mini-Mental State Examination; NINCDS-ADRDA = National Institute of Neurological and Communicative Disorders and Stroke and Alzheimer’s Disease and Related Disorders Association; PPC = posterior parietal cortex; ROI = region of interest
Received May 26, 2003. Revised August 8, 2003. Accepted October 13, 2003.
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