Unique Leg-specific Executive And Motor BOLD Activity With Visually-guided Imagery Following ACL Injury: 849 Board #28 May 31 2

Given the change in sensorimotor system activation during limited movements of the injured leg after unilateral ACL rehabilitation, we asked whether the frontostriatal network might be involved during visually-guided action-imagery. PURPOSE: To determine whether injured individuals displayed different activity during a proprietary cognitive motor-oriented imagery test. METHODS: Healthy women (18-32 yr, n=19) provided written informed consent. Ten served as controls; nine others experienced unilateral ACL rupture, repair, and rehabilitation between 6 months and 5 years from the start of the study. All participants completed a proprietary attention-switching task for 4 trials of 10 repetitions. The test required subjects to react to congruent and incongruent signals prompting them to jump and land with the right or left leg. Subjects wore a camera to record first person perspectives of test performance. Brain images were acquired with a three tesla Siemens Trio MRI with TIM system. Subjects watched the cues and their first person performance while imagining themselves physically reacting/jumping in response to the cues. A three-dimensional magnetization-prepared rapid gradient-echo (MP-RAGE) sequence acquired whole-brain structure. Voxel size was set at 1.0mm3 for structural scans and 3.0mm3 for functional scans. Significant clusters were included if meeting a six-voxel cluster threshold. A false discovery rate (FDR) threshold was set at q=0.05. Map clusters were then converted to voxels of interest, and small cluster suppression highlighted the most affected brain regions. RESULTS: Occipital activity increased in response to visual cues. BOLD signal increased in the prefrontal cortex, primary somatosensory cortex, and the primary, pre, and supplementary motor areas (p<0.01). Activity was lower in ACLs than controls, particularly when using the injured leg. However, activity was increased in the right dorsolateral prefrontal cortex in both groups, with more pronounced increases in the injured group; the highest dlPFC activity was observed when participants imagined jumping and landing with their injured leg. CONCLUSIONS: Prefrontal regions of the brain display heightened activity after ACL individuals, whereas motor regions tend to display decreased activity compared to controls.