Disordered Tactile Force Perception in Parkinson's Disease (P07.187)

Abstract

Objective: The purpose of this study is to learn if participants with Parkinson9s (PD) over estimate the magnitude of weak tactile stimuli. Perhaps in PD the perceived magnitudes of sensory events are increased, leading to the hypometric response. Alternatively, people with PD may have frontal dysfunction with impaired ability to disengage attention, producing a perceptual grasp such that the perception of stimuli with high or low intensity will be perceived as having a reduced range of magnitudes (regression to the mean). Background People with Parkinson9s disease (PD) have motor and cognitive hypometria that cannot be fully explained by alterations of efferent motor signals. Design/Methods: To determine if magnitude estimation of tactile stimuli is altered in PD, we used von Frey hairs made of nylon monofilaments. For each trial a standard monofilament was applied to the skin on the palm and the participant was told its magnitude was 50. Then, a second monofilament was applied and the participant was asked to provide a numerical estimate of the magnitude of the second stimulus relative to the first. We tested 13 people with PD and 7 control participants. Steven9s Power Law applied to responses made for stimuli lower in intensity than the standard. Results: When compared to controls, participants with PD over-estimated the magnitudes of stimulus intensities below the standard stimulus. Conclusions: Our results indicate that participants with PD overestimate the magnitudes of weak stimuli, the direction consistent with hypometric responses. These findings do not rule out perceptual grasp. Further studies assessing estimated magnitudes for stimuli having greater intensities than the standard will reveal whether consistent overestimation or reduced range of estimates account for this change. Disclosure: Dr. Kesayan has nothing to disclose. Dr. Falchook has nothing to disclose. Dr. Williamson has nothing to disclose. Dr. White has received (royalty or license fee or contractual rights) payments from patents. Dr. White has received research support from Neuromuscular Engineering, Inc. Dr. Skidmore has nothing to disclose. Dr. Heilman has received personal compensation for activities with law firms as a consultant.Dr. Heilman has received personal compensation in an editorial capacity for Journal Watch.