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Influence of performance feedback on motor cortex excitability and motor learning


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Smyth, CJ 2010 , 'Influence of performance feedback on motor cortex excitability and motor learning', PhD thesis, University of Tasmania.

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Primary motor cortex (Ml ) plays a role in motor learning, although the exact
nature of that involvement remains unclear. Refinement of the relationship between
plastic change of Ml and learning is of clinical importance in terms of understanding
and facilitating functional recovery/improvement for stroke and psychiatric disorders
with movement dysfunction ( Schizophrenia, for example). In order to optimise
symptom improvement for these individuals, it is important to determine which
movement characteristics and practice environment variables are effective in facilitating
cortical change; aspects which remain unclear. Results of prior research indicate that the
depth of processing that occurs as a result of the complexity of the motor task may be
one such factor which influences cortical plasticity and learning success. This
possibility was investigated in the present thesis by manipulating learning conditions
(augmented feedback) and the biomechanical complexity of tasks. Transcranial
magnetic stimulation (TMS) protocols were used to measure cortical excitability.
A low-complexity thumb-abduction force task was examined in Experiment 1.
Although performance of this task improved during acquisition, no evidence of cortical
change (measured as cortical excitability) was evident. Furthermore, performance was
examined at a post-24 hour retention test, where it was found that performance
improvements had not been retained. Again, cortical change was not evident. In
Experiment 2, the cognitive complexity of a similar task was increased, and varied
between-groups according to the frequency with which augmented performance
feedback was available during acquisition. Again, performance improvements during
acquisition were not accompanied by cortical change, despite the group receiving more
frequent feedback performing better than the reduced frequency feedback group.
Performance again deteriorated at retention testing, indicating that learning did not occur. These experiments provide evidence to suggest that improvements in the
performance of the force production tasks of varying complexity may not be strongly
dependent on modulations of MI cortical excitability.
A waveform tracking task of increased biomechanical and cognitive complexity
was examined in Experiment 3. Acquisition conditions again varied between-groups
according to feedback frequency. Performance improvements following acquisition
were maintained to 24 hour-retention testing for the reduced feedback frequency group,
evidencing learning. Furthermore, this skill maintenance was accompanied by increased
excitability at retention relative to the end of acquisition. This suggests that Ml may
play a role in the offline consolidation and retention of acquired complex motor skill.
The nature of Ml modulation associated with the practice, acquisition and
retention of a novel motor skill appears to vary with the nature and complexity of task
requirements. This may have implications for structuring motor learning programs
aimed at optimising cortical change and symptom improvement in movement disorders.

Item Type: Thesis - PhD
Authors/Creators:Smyth, CJ
Keywords: motor cortex, motor learning, cortical plasticity, learning conditions, biomechanical complexity of tasks
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