Background: Restless legs syndrome (RLS) is characterized by abnormal leg sensations and an uncontrollable urge to move the lower extremities during rest periods. Evidence suggests that reflex tasks that involve sensory-motor integration may be altered in RLS patients. This led us to determine if RLS patients show alterations in a sensory-motor reflex conditioning task called differential eyeblink conditioning. Methods: RLS subjects were washed out of treatment medication for 7 days prior to testing. Subjects (20 RLS and 19 Control) received 120 discrimination conditioning trials consisting of 60 CS+ trials (i.e., an auditory stimulus paired with the airpuff-US separated by a silent 900 ms trace interval) and 60 CS- trials (i.e., a different auditory stimulus that was NOT paired with the US). Results: Control subjects showed normal differential responding to the CS+ and CS-, but the RLS patients showed little or no differential responding. A post-test questionnaire provides evidence that symptomatic interference was not responsible for the eyeblink conditioning deficits in the RLS subjects, and further suggests that neurophysiological factors were responsible for these deficits. Conclusions: Together these results suggest that deficits in eyeblink conditioning are related to the pathophysiology of RLS. The eyeblink conditioning test may also be useful for supporting a clinical diagnosis or treatment strategy for RLS.
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