10 research outputs found

    Impaired perception of surface tilt in progressive supranuclear palsy

    No full text
    <div><p>Introduction</p><p>Progressive supranuclear palsy (PSP) is characterized by early postural instability and backward falls. The mechanisms underlying backward postural instability in PSP are not understood. The aim of this study was to test the hypothesis that postural instability in PSP is a result of dysfunction in the perception of postural verticality.</p><p>Methods</p><p>We gathered posturography data on 12 subjects with PSP to compare with 12 subjects with idiopathic Parkinson’s Disease (PD) and 12 healthy subjects. Objective tests of postural impairment included: dynamic sensory perception tests of gravity and of surface oscillations, postural responses to surface perturbations, the sensory organization test of postural sway under altered sensory conditions and limits of stability in stance.</p><p>Results</p><p>Perception of toes up (but not toes down) surface tilt was reduced in subjects with PSP compared to both control subjects (p≤0.001 standing, p≤0.007 seated) and subjects with PD (p≤0.03 standing, p≤0.04 seated). Subjects with PSP, PD and normal controls accurately perceived the direction of gravity when standing on a tilting surface. Unlike PD and control subjects, subjects with PSP exerted less postural corrective torque in response to toes up surface tilts.</p><p>Discussion</p><p>Difficulty perceiving backward tilt of the surface or body may account for backward falls and postural impairments in patients with PSP. These observations suggest that abnormal central integration of sensory inputs for perception of body and surface orientation contributes to the pathophysiology of postural instability in PSP.</p></div

    Postural motor control: Forward platform translation.

    No full text
    <p>CoP displacement in response to forward platform translations. A) Group raw data mean±SEM B) Group mean±SEM. CoP: center of pressure, CoM: center of mass; AP: anterior-posterior.</p

    Functional Reorganization of the Locomotor Network in Parkinson Patients with Freezing of Gait

    No full text
    <div><p>Freezing of gait (FoG) is a transient inability to initiate or maintain stepping that often accompanies advanced Parkinson’s disease (PD) and significantly impairs mobility. The current study uses a multimodal neuroimaging approach to assess differences in the functional and structural locomotor neural network in PD patients with and without FoG and relates these findings to measures of FoG severity. Twenty-six PD patients and fifteen age-matched controls underwent resting-state functional magnetic resonance imaging and diffusion tensor imaging along with self-reported and clinical assessments of FoG. After stringent movement correction, fifteen PD patients and fourteen control participants were available for analysis. We assessed functional connectivity strength between the supplementary motor area (SMA) and the following locomotor hubs: 1) subthalamic nucleus (STN), 2) mesencephalic and 3) cerebellar locomotor region (MLR and CLR, respectively) within each hemisphere. Additionally, we quantified structural connectivity strength between locomotor hubs and assessed relationships with metrics of FoG. FoG+ patients showed greater functional connectivity between the SMA and bilateral MLR and between the SMA and left CLR compared to both FoG− and controls. Importantly, greater functional connectivity between the SMA and MLR was positively correlated with i) clinical, ii) self-reported and iii) objective ratings of freezing severity in FoG+, potentially reflecting a maladaptive neural compensation. The current findings demonstrate a re-organization of functional communication within the locomotor network in FoG+ patients whereby the higher-order motor cortex (SMA) responsible for gait initiation communicates with the MLR and CLR to a greater extent than in FoG− patients and controls. The observed pattern of altered connectivity in FoG+ may indicate a failed attempt by the CNS to compensate for the loss of connectivity between the STN and SMA and may reflect a loss of lower-order, automatic control of gait by the basal ganglia.</p></div

    Structural connectivity ROIs in the A) sagittal, B) coronal, and C) axial plane.

    No full text
    <p>The SMA, as defined by Mayka et(2006) is shown in blue. The STN, as defined by Prodoehl et al (2008) is shown in yellow. The MLR, as defined by Fling et al. (2013), is shown in purple. All ROIs are overlaid on the MNI 1 mm template and are displayed in neurologic convention (right = right). Similar ROIs for the SMA and MLR were used in the left hemisphere (not displayed here).</p

    Structural connectivity between the SMA and right STN, as assessed by diffusion tensor imaging.

    No full text
    <p><b>A)</b> Normalized z-scores for structural connectivity strength between the rSTN – SMA. HC have significantly greater connectivity than either FoG− or FoG+. <b>B)</b> Rendered fiber tracts (red) from one healthy control demonstrating the structural connectivity within the hyperdirect loop between the SMA and STN (both displayed in green). *<i>P</i><0.05. HC = healthy controls.</p

    Functional connectivity strength between the SMA and the other locomotor hubs.

    No full text
    <p>FoG+ patients show greater connectivity to the MLR and CLR, but reduced connectivity to the STN. **<i>P</i><0.001, *<i>P</i><0.05.</p

    Locomotor hubs used as regions of interest for functional connectivity analysis.

    No full text
    <p>X = 7 is chosen for display as it is the only slice on which all ROIs have some overlap. Please refer to the Methods section for coordinates describing the centroid of each sphere.</p

    Patient characteristics.

    No full text
    <p>Significant differences (<i>P</i><0.05) between PD groups, assessed by Tukey’s HSD test, are highlighted in bold. All data displayed are mean (± standard deviation). HC = healthy controls. R = right, L = left, E = equal. ST = single task, DT =  dual task condition.</p

    Associations between locomotor network functional connectivity and freezing severity.

    No full text
    <p><b>A)</b> Functional connectivity strength of the lMLR – SMA loop was positively correlated with clinical rating of FoG severity during the single task turning condition (r = 0.71). <b>B)</b> Functional connectivity strength of the rMLR – SMA loop was also positively correlated with objective sensor measurement of FoG severity during dual-task turning (0.76).</p
    corecore