Abstract
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Introduction: Adaptation, as a reduction in systematic sensorimotor errors, is a particular form of motor learning. Previous studies indicated that behavioral characteristics of motor learning (i.e. the speed of performance improvements and forgetting, and the strength of the memory consolidation) vary with movement expertise (Kast, 2016). Underlying neural mechanisms of these behavioral differences are so far unclear. Here we applied FDG PET, allowing us to assess learning-related activation pattern changes of the brain in subjects with different levels of movement expertise.
Methods: 12 handball players (experts) and 12 age-matched subjects without handball experience (novices) underwent a visuomotor adaptation to prismatic glasses. Starting with tracer injection, subjects performed 30 min of handball free-throws to a target placed 3.5 m in front of them (Leukel, 2015). Subjects were instructed to hit the target. Then, a 10-min PET scan was acquired. Each participant was scanned twice under experimental (learning) and control (without prismatic glasses) conditions in randomized order. The sessions were separated by 1 day. Changes in regional normalized FDG uptake were assessed by a full factorial design analysis with SPM 12 with a significance threshold of p < 0.005 (k > 30 voxels). Additionally, the movement error of each individual’s throw was recorded and compared between groups.
Results: We could confirm the behavioral findings of our earlier study (Kast, 2016), that experts’ rate of adaptation was slower than that of novices (p < 0.001). FDG PET in both experts and novices showed a task-related deactivation of large portions of the occipital and parts of the posterior cingulate cortices during the visuomotor adaptation. Compared to novices, experts also exhibited greater deactivation of right primary auditory cortex during adaptation. Experts activated parts of the right anterior prefrontal and inferior temporal cortices more than novices, whereas novices showed stronger activation of the anterior cingulate and inferior frontal regions.
Conclusions: This is the first visuomotor adaptation study that allowed to record brain activation patterns without restriction of large movements. Marked deactivation of the visual cortex during visual adaptation in both groups suggests that the brain ‘shuts down’ conflicting visual inputs caused by prism glasses in order to adapt. Beyond this, we found different activation and deactivation patterns in experts and novices, which strengthens the assumption of different mechanisms that underlie behavioral differences associated with movement expertise. References: Kast V., Leukel C. Motor Experts Care about Consistency and Are Reluctant to Change Motor Outcome. PLoS One. 2016 Aug 30; 11(8):e0161798. doi: 10.1371/journal.pone.0161798. eCollection 2016. Leukel C., Gollhofer A., Taube W. In Experts, underlying processes that drive visuomotor adaptation are different than in Novices. Front Hum Neurosci. 2015 Feb 10; 9:50. doi: 10.3389/fnhum.2015.00050. eCollection 2015.