Identifying the neural correlates of anticipatory postural control: a novel fMRI paradigm

Abstract

ABSTRACTIntroductionPostural control is essential for maintaining body equilibrium during voluntary limb movement. Altered postural control in the trunk and hip musculature is a characteristic of aging and of multiple neurological and musculoskeletal conditions. Due to the difficulty of designing a task for the MRI environment that elicits postural activation in the trunk/hip musculature, it has not previously been possible to determine if altered cortical and subcortical sensorimotor brain activation underlies observed impairments in postural control in patient populations. The purpose of this study was to use a novel fMRI-compatible paradigm to identify the sensorimotor brain activation associated with anticipatory postural control in the trunk and hip musculature in healthy adults.MethodsBOLD fMRI imaging was performed on 20 healthy volunteers (23 ± 4 years, 13 female, 7 male, Siemens Prisma 3T MRI). Participants performed two versions of a lower limb task involving lifting the left leg a short distance to touch the foot to a horizontal target. For the supported leg raise task (SLR) the leg is raised from the knee while the thigh remains supported. For the unsupported leg raise task (ULR) the leg is raised from the hip. Anticipatory postural muscle activation is elicited in the bilateral abdominal and contralateral hip extensor musculature during the ULR but not the SLR. Thirty-two repetitions were completed for each task in response to visual cues using an event-related design. Data were processed using SPM12 and framewise head displacement was quantified using the Artifact Detection Tool. Anatomical masks for primary and secondary sensory and motor cortical regions and for the cerebellum and basal ganglia were created using WFU-PickAtlas for the right and left sides separately.ResultsFramewise head displacement was within acceptable limits for both tasks (SLR 0.27 ± 0.1mm, ULR 0.18 ± 0.1 mm). Significant brain activation during the SLR task occurred predominantly in the right primary and secondary sensorimotor cortical regions. Brain activation during the ULR task occurred bilaterally in the primary and secondary sensorimotor cortical regions, as well as cerebellum and putamen. In comparison with the SLR, the ULR was associated with significantly greater activation in the right premotor/SMA, left primary motor and cingulate cortices, primary somatosensory cortex, supramarginal gyrus/parietal operculum, superior parietal lobule, cerebellar vermis, and bilateral cerebellar hemispheres.ConclusionsCortical and subcortical regions activated during the unsupported leg raise, but not during the supported leg raise, were consistent with the planning, execution, and sensory experience of a task involving multi-segmental and bilateral postural control. This paradigm provides a foundation for future studies that will isolate neural mechanisms underlying impaired postural control in patients with neurological and musculoskeletal dysfunction.