Hypometric allocentric and egocentric distance estimates in Parkinson disease.
OBJECTIVE
Persons with Parkinson disease (PD) show hypometric movements and make hypometric estimates of imagined actions. These deficits may be related to misestimates of the length of body parts. Our objective was to learn whether patients with PD are impaired in their estimations of their arm's length and standard units of distance.


METHODS
We tested 20 patients with PD, all on therapeutic doses of dopaminergic medications, and 13 healthy controls. In half of the trials, the participants stood so that either their right or left shoulder was adjacent to a wall; in the other half, their right or left shoulder was 5 feet from the wall. In the egocentric testing condition, they were asked to move their body toward or away from the wall to what they considered was an arm's length from the wall. In the allocentric testing condition, they were to move toward or away from the wall so that their proximal shoulder was a standard unit distance of 1, 2, or 3 feet from the wall.


RESULTS
The patients with PD made much greater hypometric (too close to the wall) errors. Since at 5 feet from the wall they had to move farther to underestimate distances, their errors cannot be explained by hypometric movements. The results did not differ significantly by egocentric or allocentric estimation, side of shoulder proximity, or side of PD onset.


CONCLUSIONS
Our findings support the idea that the egocentric and allocentric hypometria associated with PD is a perceptual rather than motor disorder.
*Department of Neurology, Drexel University College of Medicine, Philadelphia, PA †Department of Neurology, University of Florida, College of Medicine, Gainesville, FL ‡Malcom Randall Veterans Affairs Hospital, Gainesville, FL §Division of Clinical Psychology and Neuropsychology, Institute of Psychology, University of Gdansk, Gdansk, Poland.
Anahid
A
Kabasakalian
Tigran
T
Kesayan
John B
JB
Williamson
Frank M
FM
Skidmore
Adam D
AD
Falchook
Michal
M
Harciarek
Kenneth M
KM
Heilman
D000203:Activities of Daily Living; D000368:Aged; D000704:Analysis of Variance; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007092:Imagination; D007858:Learning; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications* / Q000188:drug therapy / Q000503:physiopathology*; D010468:Perceptual Disorders / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D013028:Space Perception