Magnetic misreaching.
Ms D., a 76 year-old woman with a slowly progressive bilateral parietal lobe degeneration, showed an unusual variant of misreaching as yet unreported. When required to reach to a target in extrafoveal vision, she slavishly reached straight to the foveal fixation point instead ("magnetic misreaching"). Three dimensional recordings of limb movements to foveal and extrafoveal targets revealed that her reach endpoints were determined by the place she was looking, independent of the distance between target and fixation point. The sign was present in both hands. Magnetic misreaching differs from motor misbehaviours which follow frontal lobe damage. The neuropsychological and behavioural profile of Ms D., coupled with neuroimaging evidence suggest that magnetic misreaching is a manifestation of parietal lobe dysfunction.
Carey
D P
DP
Department of Psychology, University of Aberdeen, Old Aberdeen, Scotland. d.carey@abdn.ac.uk
Coleman
R J
RJ
Della Sala
S
S
D000368:Aged; D003072:Cognition Disorders / Q000209:etiology / Q000523:psychology*; D005260:Female; D005403:Fixation, Ocular / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D019636:Neurodegenerative Diseases / Q000473:pathology / Q000503:physiopathology / Q000523:psychology*; D010296:Parietal Lobe / Q000473:pathology* / Q000503:physiopathology; D011597:Psychomotor Performance / Q000502:physiology; D013028:Space Perception / Q000502:physiology*; D015899:Tomography, Emission-Computed, Single-Photon