Implicit motor learning paradigms aim to minimise verbal-analytical engagement during motor performance. Some do this by suppressing working memory activity during practice. This reduces the ability of the learner to use, manipulate and store task-related information via mental processes, such as hypothesis testing. Implicit motor learning paradigms that suppress working memory indirectly are not always effective, because individual differences, such as motivation, can override their efficiency. The aim of this thesis was to investigate whether two more direct methods, cognitive fatigue and hand contractions, are viable tools with which to suppress working memory activity during motor practice, and whether they cause reduced verbal-analytical engagement in motor performance.
Chapter 2 investigated whether a computer-based cognitive fatigue task suppressed working memory activity during a golf putting task. Behavioural measures of verbal-analytical engagement were employed to test whether the cognitive fatigue task reduced hypothesis testing during the subsequent golf putting task. Results revealed that the computer-based cognitive fatigue task promoted cognitive fatigue, but was not sufficient to cause reduced hypothesis testing compared to a non-fatigue group.
In Chapter 3, a cognitive fatigue task with greater emphasis on motor control was therefore designed. It was first established whether the task caused cognitive fatigue and if working memory functions were disrupted. Subsequently, it was established whether the cognitive fatigue task reduced hypothesis testing during performance of a novel shuffleboard task, using behavioural measures, including self-report and assessment of technique changes. Additionally, verbal-analytical engagement in motor planning was gauged, using electroencephalography (EEG) to assess alpha power over the left temporal verbal-analytical (T7) site plus connectivity between the T7 and Fz (motor planning mid-frontal) sites. The results revealed that the motor-specific cognitive fatigue manipulation caused increased, rather than decreased, verbal-analytical engagement in motor performance, compared to a no fatigue control condition.
Chapter 4 examined whether hand contraction protocols influenced cognitive processes during motor performance, by using EEG to gauge verbal-analytical engagement during motor planning (i.e., T7-Fz connectivity) following a left-hand, right-hand or no hand-contraction protocol. The findings revealed that left-hand contractions, which are thought to activate the less verbal right hemisphere and deactivate the more verbal left hemisphere, caused reduced verbal-analytical engagement in motor planning, compared to the other protocols. Furthermore, right-hand contractions caused higher levels of verbal-analytical engagement in motor planning. Consequently, Chapter 5 investigated whether left-hand contractions promoted implicit motor learning. Participants practiced a motor task following regular bouts of left-hand contractions, right-hand contractions or no hand-contractions. Behavioral measures were used to gauge the extent to which verbal-analytical engagement was curtailed or encouraged. The results revealed no evidence that left-hand contractions promoted implicit motor learning, and both left-hand and right-hand contractions caused worse performance than no hand-contractions during a post-practice test phase.
Working memory performance was disrupted by both the cognitive fatigue and hand contraction protocols; however, predicted decrements in verbal-analytical engagement did not occur, and implicit motor learning was not promoted. The findings of this thesis reveal the complexity of the interrelationships between working memory, verbal-analytical processes and brain activity during motor learning. Future directions for research are considered.
