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

Abstract

Thirteen non-demented patients with Parkinson's disease (PD) were compared with age matched controls on two standard tests of implicit learning. A verbal version of the Serial Reaction Time (SRT) task was used to assess sequence learning and an artificial grammar (AG) task assessed perceptual learning. It was predicted that PD patients would show implicit learning on the AG task but not the SRT task, as motor sequence learning is thought to be reliant upon the basal ganglia which is damaged in PD. Patients with PD demonstrated implicit learning on both tasks. In light of these unexpected results the research on SRT learning in PD is reconsidered, and some possible explanations for the sometimes conflicting results of PD patient samples on the SRT task are considered. Factors which merit further study in this regard are: The degree to which the SRT task relies on overt motor responses; the effects of frontal lobe dysfunction upon implicit sequence learning; and the degree to which the illness itself has advanced.

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.…”

“…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).…”

The Differential Role of Premotor Frontal Cortex and Basal Ganglia in Motor Sequence Learning: Evidence From Focal Basal Ganglia Lesions

“…Subjects in later stages of PD, with bilateral involvement, or subjects with additional frontal type deficits were the most affected (Jackson et al 1995;Doyon et al 1997). However, there are also reports of preserved implicit learning of PD subjects in the SRTT (Smith et al 2001). Even in those investigations that demonstrated less implicit learning in PD or HD subjects than in normal controls, basal ganglia subjects still showed a substantial decrease in reaction times in response to a repeating sequence and a slowing of responses when a random block was introduced.…”

Implicit learning of a repeated segment in continuous tracking: A reappraisal

“…After some amount of practice, performance of participants on the repeated sequence is generally better than performance on a new sequence. In recent years, a huge number of studies using SRT tasks have improved our knowledge about various issues, such as the implicit-learning abilities of children (e.g., Meulemans, Van Der Linden, & Perruchet, 1998), elderly people (e.g., Curran, 1997), and neurologically impaired patients (e.g., Smith, Siegert, McDowall, & Abernethy, 2001), the relationships between performance and explicit knowledge (e.g., Shanks & Perruchet, 2002), and the relationships between perceptual and motor components of learning (e.g., Kelly, Burton, Riedel, & Lynch, 2003).…”