Brain networks associated with anticipatory postural adjustments in Parkinson's disease patients with freezing of gait

High-frequency rTMS over bilateral primary motor cortex improves freezing of gait and emotion regulation in patients with Parkinson's disease: a randomized controlled trial

Background

Freezing of gait (FOG) is a common and disabling phenomenon in patients with Parkinson's disease (PD), but effective treatment approach remains inconclusive. Dysfunctional emotional factors play a key role in FOG. Since primary motor cortex (M1) connects with prefrontal areas via the frontal longitudinal system, where are responsible for emotional regulation, we hypothesized M1 may be a potential neuromodulation target for FOG therapy. The purpose of this study is to explore whether high-frequency rTMS over bilateral M1 could relieve FOG and emotional dysregulation in patients with PD.

Methods

This study is a single-center, randomized double-blind clinical trial. Forty-eight patients with PD and FOG from the Affiliated Hospital of Xuzhou Medical University were randomly assigned to receive 10 sessions of either active (N = 24) or sham (N = 24) 10 Hz rTMS over the bilateral M1. Patients were evaluated at baseline (T0), after the last session of treatment (T1) and 30 days after the last session (T2). The primary outcomes were Freezing of Gait Questionnaire (FOGQ) scores, with Timed Up and Go Test (TUG) time, Standing-Start 180° Turn (SS-180) time, SS-180 steps, United Parkinson Disease Rating Scales (UPDRS) III, Hamilton Depression scale (HAMD)-24 and Hamilton Anxiety scale (HAMA)-14 as secondary outcomes.

Results

Two patients in each group dropped out at T2 and no serious adverse events were reported by any subject. Two-way repeated ANOVAs revealed significant group × time interactions in FOGQ, TUG, SS-180 turn time, SS-180 turning steps, UPDRS III, HAMD-24 and HAMA-14. Post-hoc analyses showed that compared to T0, the active group exhibited remarkable improvements in FOGQ, TUG, SS-180 turn time, SS-180 turning steps, UPDRS III, HAMD-24 and HAMA-14 at T1 and T2. No significant improvement was found in the sham group. The Spearman correlation analysis revealed a significantly positive association between the changes in HAMD-24 and HAMA-14 scores and FOGQ scores at T1.

Conclusion

High-frequency rTMS over bilateral M1 can improve FOG and reduce depression and anxiety in patients with PD.

Cognitive and emotional factors influence specific domains of postural control in individuals with moderate-to-severe Parkinson's disease

INTRODUCTION

Cognition and emotional state are domains that highly interfere with postural control in individuals with Parkinson's disease (PD). This study aims to find associations between executive function, anxiety, depression, and reactive and anticipatory postural control domains in individuals with moderate-to-severe Parkinson's disease.

METHODS

In this study, 34 individuals with PD while on medication were thoroughly assessed for postural control in perturbed, quiet standing and stepping. We performed multiple linear stepwise regressions using postural variables as dependent and cognitive/emotional as independent variables.

RESULTS

The results showed that cognitive flexibility explained 23 % of anticipatory postural adjustments (APA) duration, inhibitory control explained 42 % of instability on a malleable surface, anxiety explained 21 % of APA amplitude, and 38 % of reactive postural response amplitude.

CONCLUSION

Our results highlight the impact of emotional and cognitive states on particular domains of postural control in individuals with PD while on medication. These results may have significant implications for future treatments, mainly considering the predictors for postural control domains, which were consistent with the assumption that impairments in affective and executive domains underlie posture. As we have shown that cognitive and emotional states influence postural control domains in individuals with PD, this should be taken into account in rehabilitation protocols.

Impaired structural and reserved functional topological organizations of brain networks in Parkinson's disease with freezing of gait

Background

Freezing of gait (FOG) is a common disabling motor disturbance in Parkinson's disease (PD). Our study aimed to probe the topological organizations of structural and functional brain networks and their coupling in FOG.

Methods

In this cross-sectional retrospective study, a total of 30 PD patients with FOG (PD-FOG), 40 patients without FOG, and 25 healthy controls (HCs) underwent clinical assessments and magnetic resonance imaging (MRI) scanning. Large-scale structural and functional brain networks were constructed. Subsequently, global and nodal graph theoretical properties and functional-structural coupling were investigated. Finally, correlations between the altered brain topological properties and freezing severity were analyzed in PD-FOG.

Results

For structural networks, at the global level, PD-FOG exhibited increased normalized characteristic path length (P=0.040, Bonferroni-corrected) and decreased global efficiency (P=0.005, Bonferroni-corrected) compared with controls, and showed reduced global (P=0.001, Bonferroni-corrected) and local (P=0.032, Bonferroni-corrected) efficiency relative to patients without FOG. At the nodal level, nodal efficiency of structural networks was reduced in PD-FOG compared with PD patients without FOG, located in the left supplementary motor area (SMA), gyrus rectus, and middle cingulate cortex (MCC) (all P<0.05, Bonferroni-corrected). Notably, altered global and nodal properties of structural networks were significantly correlated with Freezing of Gait Questionnaire scores [all P<0.05, false discovery rate (FDR)-corrected]. However, only an increase in local efficiency (P=0.003, Bonferroni-corrected) of functional networks was identified in PD-FOG compared with those without FOG. No significant structural-functional coupling was detected among the 3 groups.

Conclusions

This study demonstrates the extensively impaired structural and relatively reserved functional network topological organizations in PD-FOG. Our results also provide evidence that the pathogenesis of PD-FOG is primarily attributable to network vulnerability established by crucial structural damage, especially in the left SMA, gyrus rectus, and MCC.

Human Standing Posture Motion Evaluation by the Visual Simulation of Multi-Directional Sea-Waves

Crew fatigue from standing posture motion, caused by ship motion, can lead to marine accidents. Therefore, the mechanism of fatigue in crew members ought to be elucidated. The standing posture of humans is maintained by postural state detection through the visual, vestibular, and somatosensory systems. Humans can adjust their posture through corrective postural reactions (CPR) generated after anticipatory postural adjustments (APAs) by using information from these sensory systems. APAs refer to skills acquired by learning from past motions and perturbations and are prepared by the central nervous system based on visual information before the actual perturbation occurs. We hypothesized that APAs would decrease fatigue in crew members by stabilizing their standing posture motions. We aimed to clarify the human standing posture control influenced by APAs based on visual information. To this end, we presented wave images with different wave directions to the participants using a visual simulator and analyzed their standing posture motion. We found that the participants stabilized their standing posture based on the projected wave directions. This showed that the participants predicted ship motion from the wave images and controlled their center of pressure (COP) through APAs. Individual differences in standing postural motion may indicate the subjective variation of APAs based on individual experiences. This study was limited to males aged 20-23 years. To generalize this study, randomized controlled trials should be performed with participants of multiple age groups, including men and women.

A Novel Viewpoint on the Anticipatory Postural Adjustments During Gait Initiation

Anticipatory postural adjustments (APAs) are the coordinated muscular activities that precede the voluntary movements to counteract the associated postural perturbations. Many studies about gait initiation call APAs those activities that precede the heel-off of the leading foot, thus taking heel-off as the onset of voluntary movement. In particular, leg muscles drive the center of pressure (CoP) both laterally, to shift the body weight over the trailing foot and backward, to create a disequilibrium torque pushing forward the center of mass (CoM). However, since subjects want to propel their body rather than lift their foot, the onset of gait should be the CoM displacement, which starts with the backward CoP shift. If so, the leg muscles driving such a shift are the prime movers. Moreover, since the disequilibrium torque is mechanically equivalent to a forward force acting at the pelvis level, APAs should be required to link the body segments to the pelvis: distributing such concentrated force throughout the body would make all segments move homogeneously. In the aim of testing this hypothesis, we analyzed gait initiation in 15 right-footed healthy subjects, searching for activities in trunk muscles that precede the onset of the backward CoP shift. Subjects stood on a force plate for about 10 s and then started walking at their natural speed. A minimum of 10 trials were collected. A force plate measured the CoP position while wireless probes recorded the electromyographic activities. Recordings ascertained that at gait onset APAs develop in trunk muscles. On the right side, Rectus Abdominis and Obliquus Abdominis were activated in 11 and 13 subjects, respectively, starting on average 33 and 54 ms before the CoP shift; Erector Spinae (ES) at L2 and T3 levels was instead inhibited (9 and 7 subjects, 104 and 120 ms). On the contralateral side, the same muscles showed excitatory APAs (abdominals in 11 and 12 subjects, 27 and 82 ms; ES in 10 and 7 subjects, 75 and 32 ms). The results of this study provide a novel framework for distinguishing postural from voluntary actions, which may be relevant for the diagnosis and rehabilitation of gait disorders.

Posture Instability Is Associated with Dopamine Drop of Nigrostriatal System and Hypometabolism of Cerebral Cortex in Parkinson Disease

BACKGROUND

Posture instability (PI) is known to be a severe complication in Parkinson's disease (PD), and its mechanism remains poorly understood. Our study aims to explore the changes of brain network in PI of PD, and further investigate the role of peripheral inflammation on activities of different brain regions in PD with PI.

METHODS

167 individuals were recruited, including 36 PD cases with PI and 131 ones without PI. We carefully assessed the status of motor and cognitive function, measured serum inflammatory factors, and detected the dopaminergic pathways and the metabolism of different brain regions by positron emission tomography (PET). Data analysis was conducted by variance, univariate analysis, chi-square analysis, logistic regression, and partial correlation.

RESULT

No difference was found for age or onset age between the two groups (P>0.05). Female patients were susceptible to posture impairment and had a 2.14-fold risk for PI compared with male patients in PD (P<0.05). Patients with PI had more severe impairment of motor and cognitive function for a longer duration than those without PI (P<0.05). The mean uptake ratios of presynaptic vesicular monoamine transporter (VMAT2), which were detected in the caudate nucleus and putamen, were lower in PI group than those without PI (P<0.05). There were lower activities of the midbrain, caudate nucleus, and anterior medial temporal cortex in PI group than those in the non-PI group (P<0.05). Although serum concentrations of immunoglobulins (IgG, IgM, and IgA) and complements (C3, C4) were higher in PI group than those in the non-PI group, only serum IgM concentration had a significant difference between the two groups (P<0.05). We further explored significant inverse correlations of IgG, IgM, IgA, and C4 with activities of some cerebral cortex in PI of PD (P<0.05).

CONCLUSION

Female patients were susceptible to posture instability and had a 2.14-fold risk for PI of PD. Patients with PI had more severe impairments of motor and cognitive function for a longer duration than those without PI. PI was associated with dopamine drop of the nigrostriatal system and lower activities of the limbic cortex in PD. Peripheral inflammation may be involved in degeneration of the cerebral cortex in PD combined with PI.