Abstract
Cortical excitability may be subject to changes through training and learning. Motor training can increase cortical excitability in motor cortex, and facilitation of motor cortical excitability has been shown to be positively correlated with improvements in performance in simple motor tasks. Thus cortical excitability may tentatively be considered as a marker of learning and use-dependent plasticity. Previous studies focused on changes in cortical excitability brought about by learning processes, however, the relation between native levels of cortical excitability on the one hand and brain activation and behavioral parameters on the other is as yet unknown. In the present study we investigated the role of differential native motor cortical excitability for learning a motor sequencing task with regard to post-training changes in excitability, behavioral performance and involvement of brain regions. Our motor task required our participants to reproduce and improvise over a pre-learned motor sequence. Over both task conditions, participants with low cortical excitability (CElo) showed significantly higher BOLD activation in task-relevant brain regions than participants with high cortical excitability (CEhi). In contrast, CElo and CEhi groups did not exhibit differences in percentage of correct responses and improvisation level. Moreover, cortical excitability did not change significantly after learning and training in either group, with the exception of a significant decrease in facilitatory excitability in the CEhi group. The present data suggest that the native, unmanipulated level of cortical excitability is related to brain activation intensity, but not to performance quality. The higher BOLD mean signal intensity during the motor task might reflect a compensatory mechanism in CElo participants.
Highlights
Task training and learning can induce changes in the brain - in cortical representations [1,2] and in cortical excitability
Another study demonstrated that simple repetitive movements such as ballistic abductions of the thumb caused an increase in motor evoked potentials (MEPs) amplitude indicative of training effects [4,5]
Since primary motor cortex does control muscle activity and movements, but appears to be involved in forming new or adapting existing motor skills [9], as required in practicing of learned movements [10,11] or in learning of a new movement sequence [12], changes in cortical excitability in motor cortex might be considered a marker for motor learning and usedependent plasticity
Summary
Task training and learning can induce changes in the brain - in cortical representations [1,2] and in cortical excitability. For a variety of tasks, studies have demonstrated increases in cortical excitability after training: Motor cortex excitability was shown to increase during execution and mental imagery of sequential finger movements, but not during repetitive movements [3]. Extensive training of elementary finger tapping movements increased cortical excitability [6]. The increase in cortical excitability appears to be related to learning success: task-induced facilitation of motor evoked potentials (MEPs) was found to be positively correlated with improvements in performance [7,8]. Since primary motor cortex does control muscle activity and movements, but appears to be involved in forming new or adapting existing motor skills [9], as required in practicing of learned movements [10,11] or in learning of a new movement sequence [12], changes in cortical excitability in motor cortex might be considered a marker for motor learning and usedependent plasticity
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