Effect of click trains on duration estimates by people with Parkinson's disease.

Patients with a diagnosis of Parkinson's disease and age- and IQ-matched controls estimated the duration of short 500-Hz tones (325-1,225 ms), on trials where the tone was either preceded by 3 s of 5-Hz clicks, or presented without clicks. The click manipulation had been shown in earlier studies with student participants to make verbal estimates longer. Patients were tested both on and off their dopaminergic medication, and controls were also tested in two sessions. Verbal estimates were markedly and significantly longer on trials with clicks than on those without clicks for both the patients and the controls, but there were no significant performance differences between patients or controls, nor between the on and off medication sessions in the patients. The study shows that a manipulation of subjective time, which has had small but consistent effects in student participants, also affects timing in patients and adds to a growing body of evidence that timing in patients with Parkinson's disease may in many cases have the same characteristics as those of neurologically intact control groups.