Abstract
Knowledge of brain correlates of postural control is limited by the technical difficulties in performing controlled experiments with currently available neuroimaging methods. Here we present a system that allows the measurement of anticipatory postural adjustment of human legs to be synchronized with the acquisition of functional magnetic resonance imaging data. The device is composed of Magnetic Resonance Imaging (MRI) compatible force sensors able to measure the level of force applied by both feet. We tested the device in a group of healthy young subjects and a group of elderly subjects with Parkinson’s disease using an event-related functional MRI (fMRI) experiment design. In both groups the postural behavior inside the magnetic resonance was correlated to the behavior during gait initiation outside the scanner. The system did not produce noticeable imaging artifacts in the data. Healthy young people showed brain activation patterns coherent with movement planning. Parkinson’s disease patients demonstrated an altered pattern of activation within the motor circuitry. We concluded that this force measurement system is able to index both normal and abnormal preparation for gait initiation within an fMRI experiment.
Highlights
Knowledge of brain correlates of postural control is limited by the technical difficulties in performing controlled experiments with currently available neuroimaging methods
anticipatory postural adjustment (APA) have been thoroughly investigated in behavioral studies, and these have informed us about differences between normal and impaired gait initiation[1,2]
Most studies assessing brain function related to APAs have used manual tasks[3,4], speech articulation[5], and ankle dorsiflexion and plantiflexion[6]
Summary
We tested whether the presence of the FMS in the scanner interfered with the quality of the brain images. The young group showed smaller amplitude of the medio-lateral force (Fml) in the supported (M = 0.38 N/cm, SE = 0.01, range = 0.20–0.60) compared to the unsupported condition (M = 0.80 N/cm, SE = 0.01, range = 0.70–0.88), Z = 0, p < 0.01). The right SMA and sensorimotor cortices showed increased activation in the contrast unsupported >supported, related to the APA executed by the left leg, supporting similar results when the task separated support from the direct limb movement[7,31]. The UPDRS correlation with the fMRI was similar to the correlation with the step task (scatterplots), the analysis did not reach statistical significance rs (6) = −0.50 (p = 0.20) (Fig. 3) These results suggest that the severity of the disease impacts the amplitude of the APA as shown previously[1,35].
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