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If this was posted before, I don't remember seeing it, but then, I don't remember a lot of things anymore. jmr The Medical Post VOLUME 35, NO. 19, May 18, 1999 Parkinson's shown to affect spatial perception By Susan Jeffrey Study concludes patients see details but miss the big picture TORONTO - Parkinson's patients may have difficulty seeing the forest for the trees. Researchers at the University of Florida, Gainesville, are reporting patients with Parkinson's disease (PD) may have trouble focusing on the big picture, even though their perception of fine detail remains intact. In a case-control study, they compared responses in 11 PD patients with those in 11 age-and education-matched subjects, using test patterns of large letters made up of smaller letters, which were in turn made up of even smaller letters. The idea was to compare their perception of small details, or "spotlight" abilities, with their ability to perceive the more global picture, or the attentional "flood-light," said Dr. Anna Barrett, a visiting research assistant professor of neurology at the University of Florida, and a consulting neurologist at the Veterans Affairs Medical Centre in Gainesville. Research published in 1979 had shown that subcortical lesions interrupting dopaminergic transmission resulted in an attentional deficit in rats that could be manipulated pharmacologically with dopamine, Dr. Barrett said. They set out to investigate whether a similar attentional deficit existed in patients with Parkinson's disease, where the primary deficit is a depletion of dopamine. Each subject was shown five sheets with these letters-within-letters printed on them, at two distances - 30 cm and 75 cm - and were asked to tell the reviewer each of the different letters they saw. They were allowed to continue until they felt they'd named all the letters on the sheet. "At the small letter size and the medium letter size, when you do a pair-wise comparison with the control subjects, there's no difference," Dr. Barrett said. "However, Parkinson's subjects only recognized 24.5% of the large letters, while the controls recognized 65.6%." The difference was statistically significant, she added. "We found that Parkinson's disease adversely affects perception of large or global spatial configurations in our subjects." Previous work has suggested normal subjects are perceptually biased to perceive the big picture over fine details, she added. "Dopamine depletion may alter these perceptual attentional biases and . . . a narrowed area over which subjects can spread their perceptual attention or a 'narrowed attentional floodlight.' " However, it did not appear the patients understood they had this deficit, Dr. Barrett said. Generally, a study administrator must be careful not to give subjects cues as to what is expected of them. However, even with cues, PD patients in this study did not feel they needed to look further, even though they had not seen the largest letters. "I would say it's quite conceivable there may be some relationship between this kind of a problem and some difficulty with handling things that require them to look over a large spatial area, such as handling themselves in a crowded supermarket." © Copyright 1999 The Medical Post. All rights reserved. -- Judith Richards, London, Ontario, Canada [log in to unmask]