Incidental motor sequence learning: Investigations into its cognitive basis and the effects of neurological impairment and treatment

Abstract

To survive in a complex changing environment humans frequently need to adapt their behaviour incidentally from normal interactions in the environment without any specific intention to learn. Whilst there is a considerable body of research into incidental learning of sequential information there is still fundamental debate regarding its cognitive basis, the associated neural mechanisms and the way in which it is affected by neurological disease. These issues were explored, in normal participants and neurological patients, using manipulations of the Serial Reaction Task [SRT] in which participants gradually learn a stimulus sequence (usually screen locations) after responding to each item by pressing corresponding response buttons. The first two experiments (chapter 3) demonstrate that the specific metric used to quantify learning and the occurrence of highly salient repeat locations may inflate estimates of learning in tasks with increased motor demands. The next three experiments (chapter 4) examine whether a secondary (not directly behaviourally relevant) information source during the SRT facilitates chunking in memory and overall learning. In a spatial SRT task (specified by horizontal location), additional spatial information (vertical location) enhanced learning but a secondary perceptual property (colour) produced a cost. However, in a perceptual SRT a secondary perceptual property (colour) had no effect. The next study demonstrates that impairments of incidental learning in Parkinson’s disease are partially reduced by administration of l-Dopa. Implications for models of striatal function and studies suggesting implicit learning is impaired by l-Dopa are discussed. Finally, the impact of Deep Brain Stimulation of the GPi is investigated in a population known to have only limited cognitive deficits relating to their illness (dystonia). Despite previous reports of impaired intentional learning in participants with a high genetic risk of Dystonia, there was no evidence for any impairment before or after stimulation. Implications across studies and future research directions are also discussed.