Visuomotor skill learning on serial reaction time task in patients with early Parkinson's disease

Selective impairments in implicit learning in Parkinson's disease

“…As in many other studies, the results have not been consistent, with one group of subjects showing learning (Smith et al, 2001), while in another group there was no effect (Westwater et al, 1998). Such mixed results across studies, combined with the finding that the clinical stage of the disease does not seem to influence the rate or the magnitude of implicit learning in PD (Stefanova et al, 2000), imply that the extent of motor symptoms is not related to the amount of implicit learning that occurs. Indeed, it has been shown that PD patients are impaired at implicit learning in nonmotor tasks as well (Knowlton et al, 1996).…”

“…However, inconsistency of impairments observed in patients with Parkinson's disease (PD), who have significant dysfunction of the basal ganglia, have raised the issue of whether these structures play a crucial role in implicit sequence learning or merely modulate the expression of the learning. Although some studies have found these patients to have profound implicit learning deficits (Pascual-Leone et al, 1993;Jackson et al, 1995;Doyon et al, 1997;Stefanova et al, 2000), others observed either no (Smith et al, 2001) or only mild to moderate impairments (Pascual-Leone et al, 1993;Sommer et al, 1999;Ferraro et al, 1993;Shin and Ivry, 2003).…”

“…This position is supported by the finding that patients with PD may show evidence of learning in the serial reaction time (SRT) task on the basis of errors, without a concomitant decrease in RT (Sommer et al, 1999). However, the fact that neither the degree of cognitive impairment (Ferraro et al, 1993;Stefanova et al, 2000) nor the clinical stage of the disease (Stefanova et al, 2000) appears to influence the rate or the magnitude of implicit learning in PD suggests that this overall conclusion is tenuous.…”

Demonstration of nondeclarative sequence learning in mice: Development of an animal analog of the human serial reaction time task: Figure 1.

“…Parkinson's (PD) and Huntington's diseases (HD), which both disturb basal ganglia function, result in deficits in SRT performance differentiated only by degree. The typical pattern of behavior in PD patients performing the SRT is, firstly, slower reaction times during sequence acquisition, and secondly, and more importantly, a markedly weaker interference effect (compared to controls) when switched from a repeating to a random sequence (Ferraro et al 1993; PascualLeone et al 1993;Jackson et al 1995;Westwater et al 1998;Sommer et al 1999;Stefanova et al 2000). Subjects with HD show a similar, but more extreme, impairment in the SRT.…”

“…Learning is assessed by observing a deterioration in task performance when a random sequence replaces a regularly repeating sequence (the "interference effect"). Subjects with basal ganglia disorders such as Huntington's disease (Knopman and Nissen 1991;Willingham and Koroshetz 1993), Parkinson's disease (Ferraro et al 1993;Pascual-Leone et al 1993;Jackson et al 1995;Westwater et al 1998;Sommer et al 1999;Stefanova et al 2000) or pharmacologic treatments that affect the basal ganglia (Knopman 1991) demonstrate greatly reduced, or entirely absent, interference effects, indicating compromised implicit learning. These SRT deficits in subjects with basal ganglia dysfunction are not simply due to motor performance dysfunction (Harrington et al 1990), as subjects with damage restricted to the basal ganglia as a consequence of infarct or hemorrhage are significantly impaired in both a motor and nonmotor version of the SRT (Vakil et al 2000).…”