Implicit Learning in Parkinson's Disease: Evidence from a Verbal Version of the Serial Reaction Time Task

Abstract

Evidence suggests that patients suffering from Parkinson's Disease (PD) demonstrate less sequence learning in the serial reaction time (SRT) task devised by Nissen and Bullemer (1987). One of the problems with this task is that it is motor intensive and, given the motor difficulties which characterize Parkinson's disease (e.g., tremor, impaired facility of movement, rigidity, and loss of postural reflexes), allows the possibility that patients with PD are capable of sequence learning but are simply unable to demonstrate this through a decrease in reaction time over trials. The present study examined the performance of patients with PD and healthy controls, matched for verbal fluency, on a verbal version of the SRT task where the standard button-pressing response was replaced by a spoken response. Thirteen nondementing patients with PD and 11 healthy controls were administered the SRT task. The PD group demonstrated less sequence learning than the controls and this was independent of age and severity of illness. The results add support to those studies which have found impaired sequence learning using the standard form of the SRT task.

Selective impairments in implicit learning in Parkinson's disease

“…In an effort to address the role of inherent motor expression difficulties, PD subjects have been tested by using a verbal version of the SRT task. 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.…”

Preserved Implicit Learning on Both the Serial Reaction Time Task and Artificial Grammar in Patients with Parkinson's Disease

“…The authors found no significant SRT learning in PD patients and concluded that the results suggest a role for the basal ganglia in SRT learning or the expression of serially-ordered action. Westwater et al (1998) employed a verbal version of the SRT task, designed to minimize the influence of the motor symptoms of PD, and reported similar results. In summary, there is a growing number of studies suggesting that implicit learning in PD, at least as measured by the SRT task, is reduced or impaired in people with PD.…”

“…The SRT task was a verbal version of the classic SRT task, as devised by Nissen and Bullemer (1987), replicating the SRT task used by Westwater et al (1998) (refer to Westwater et al for a more detailed description of the procedure). Briefly, all participants completed five blocks of trials, each consisting of 100 trials.…”

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).…”