34 CHAPTER 2 Motor planning Motor planning will be assessed using a motor imagery task during which functional MRI signal is recorded. Motor imagery involves mental simulation of a movement, without actual execution of that movement. It can be used as a tool to generate cortical motor states without movement production. As is evident by the presence of scapular dyskinesia, peripheral motor control is altered in NA. With motor imagery, changes in central motor control can be assessed, while controlling for alterations in peripheral factors. Empirical evidence shows that first-person motor imagery tasks are sensitive to motor control variables and use central neural mechanisms involved in action planning: 30, 58, 59 A. Motor imagery task-based functional MRI i. Changes (as the result of rehabilitation and as the result of NA (assessed in the sub-study) in the neural mechanisms underlying motor planning and representations will be quantified by changes in the magnitudes of mean functional MRI signal, blood-oxygen-level-dependent (BOLD) activity associated with motor imagery during the Hand Laterality Judgment task (HLJT) (see B). ii. Analyses of the functionalMRI datawill primarily be focused on the following brain regions: the extrastriate body area, the posterior parietal cortex in the intra-parietal sulcus region, and the precentral and postcentral gyri. These a priori regions of interest for analysis of functional MRI magnitude differences are chosen based on previous research using the same motor imagery task. 24, 40, 58-60 Additionally, we will employ a whole brain exploratory analysis of functional changes in NA outside these canonical motor imagery regions (see also Exploratory outcomes). iii. Participants’ respiration will be recorded during the functional MRI scan to be able to control for noise introduced in the data. B. Performance on the motor imagery task i. The HLJT 29 assesses central representations and planning of movements involving the upper extremity. Participants are asked to judge the laterality of line drawings of hands. The hands vary in laterality (left or right), view (palmar or dorsal) and degree of rotation (rotated −135°, −105°, −75°, −45°, 45°, 75°, 105°, 135° from the upright position). Participants are instructed to use their own hands as reference (i.e. imagine moving their upper extremity to match the hand shown on screen), without actually moving their upper extremity. As participants perform this task in the MRI scanner, they cannot rely on visual information to perform the task. The task consists of 32 blocks of 8 trials. The inter-trial interval ranges from 2000 to 3000 ms. Before each block, participants are instructed to place their hands in one of four positions: both hands with palms facing up, both hands palms facing down, one hand palm up (left/right) and one hand palm down (right/left). With this manipulation, participants use of firstperson motor imagery can be checked through assessment of the posture effect: when using first person motor imagery, participants are faster for stimuli with a view that is congruent with the current posture of their own hand than for stimuli with a view that is incongruent with the posture of
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