Faculty Bibliography

BACKGROUND: In a combined animal and human study, we have previously found that a 5-day treatment that enhances cortical plasticity also facilitates brain-derived neurotrophic factor (BDNF)-tyrosine receptor kinase B (TrkB) signaling and increases activated TrkB and N-methyl-d-aspartate receptor (NMDAR) association in both the cortex and the peripheral lymphocytes. Patients with Parkinson's disease (PD), in general, show decreased cortical plasticity, as demonstrated by electrophysiological and behavioral studies. Here, we test the hypothesis that an exercise program that improves motor function and seems to slow down symptom progression can enhance BDNF-TrkB signaling in lymphocytes. METHODS: A total of 16 patients with PD underwent a 4-week multidisciplinary intensive rehabilitation treatment (MIRT), which included aerobic training and physical and occupational therapy. Blood was collected before and after 2 and 4 weeks of MIRT. Lymphocytes were isolated to examine BDNF-TrkB signaling induced by incubation with recombinant human BDNF. TrkB signaling complexes, extracellular-signal-regulated kinase-2 and protein-kinase-B were immunoprecipitated; the content of immunocomplexes was determined by Western blotting. RESULTS: After MIRT, all patients showed improvement in motor function. TrkB interaction with NMDAR and BDNF-TrkB signaling increased in peripheral lymphocytes at receptor, intracellular mediator, and downstream levels. The decrements in Unified Parkinson's Disease Rating Scale II (UPDRSII) and total scores were significantly correlated with the increases in TrkB signaling at receptor, intracellular mediator, and NMDAR interaction levels. CONCLUSIONS: The significant correlation between reduced UPDRS scores and the changes in lymphocyte activity suggest that enhanced BDNF-TrkB signaling in lymphocyte and reduced severity of PD symptoms may be related.

Epilepsy is an uncommon comorbidity of Parkinson's disease (PD) and has been considered not directly associated with PD. We present five patients (3 men and 2 women; ages 49-85) who had concomitant PD and cryptogenic epilepsy. Although rare, epilepsy can coexist with PD and their coexistence may influence the progression of PD. While this may be a chance association, an evolving understanding of the neurophysiological basis of either disease may suggest a mechanistic association.

Objective: To compare changes in clinical outcomes after weekly low-frequency (LF) repetitive transcranial magnetic stimulation (rTMS) sessions over one vs. two pre-motor cortex (preMC) areas in Parkinson's disease (PD). Background: The preMC is a key component in the complex system responsible for motor execution. Particularly, dorsal preMC (PMd) and supplementary motor area (SMA) are critically involved in PD pathogenesis due to their broad anatomical and functional connectivity with the basal ganglia and motor cortex (Buhmann et al, 2004; Shirota et al, 2013). Weekly rTMS over SMA has been determined as an effective add-on therapy for PD motor symptoms (Shirota et al, 2013). Nevertheless, the therapeutic potential of combining different premotor targets has never been tested. We designed an active controlled study to explore potential additive effects of rTMS over both SMA and PMd as compared to SMA alone. Methods: Eighteen PD patients with H&Y scores 2 and 3 participated in a parallel double-blind randomized study of four weekly sessions of LF rTMS. Outcomes were assessed at baseline and 4 weeks post-treatment completion. Stimulation arms were rTMS over SMA or rTMS over both PMd and SMA (PMd+SMA). Clinical outcomes were total UPDRS-III and axial, tremor, rigidity, and bradykinesia subsets during ON time. Results: Baseline demographic and clinical characteristics did not differ between groups. Fourteen patients, 6 SMA-alone and 8 PMd+SMA, completed all study visits. Both interventions, SMAalone and PMd+SMA, significantly decreased UPDRS-III (z=-2.21, p=0.027; z=-2.53, p=0.011, respectively). Subset analyses showed SMA-alone significantly decreased only bradykinesia subset (z=- 2.21, p=0.027) while PMd+SMA decreased both bradykinesia and axial subsets (AxS) (z=-1.98, p=0.048; z=-2.39, p=0.017, respectively). Comparison between arms showed that only PMd+SMA significantly improved AxS (U=5.5, p=0.013). [figure1] There were no significant differences in changes in total UPDRS-III or any other subset. Conclusions: Both rTMS interventions were well-tolerated and improved UPDRS-III total motor scores and bradykinesia. However, improvement in AxS was seen only in the PMd+SMA group, suggesting that LF rTMS over combined preMC areas could be an effective therapy to improve axial symptoms. Larger placebocontrolled studies need to be conducted to corroborate these findings. (Figure presented)

BACKGROUND: PD (Parkinson's disease) is characterized by impairments in cortical plasticity, in beta frequency at rest and in beta power modulation during movement (i.e., event-related ERS [synchronization] and ERD [desynchronization]). Recent results with experimental protocols inducing long-term potentiation in healthy subjects suggest that cortical plasticity phenomena might be reflected by changes of beta power recorded with EEG during rest. Here, we determined whether motor practice produces changes in beta power at rest and during movements in both healthy subjects and patients with PD. We hypothesized that such changes would be reduced in PD. METHODS: We thus recorded EEG in patients with PD and age-matched controls before, during and after a 40-minute reaching task. We determined posttask changes of beta power at rest and assessed the progressive changes of beta ERD and ERS during the task over frontal and sensorimotor regions. RESULTS: We found that beta ERS and ERD changed significantly with practice in controls but not in PD. In PD compared to controls, beta power at rest was greater over frontal sensors but posttask changes, like those during movements, were far less evident. In both groups, kinematic characteristics improved with practice; however, there was no correlation between such improvements and the changes in beta power. CONCLUSIONS: We conclude that prolonged practice in a motor task produces use-dependent modifications that are reflected in changes of beta power at rest and during movement. In PD, such changes are significantly reduced; such a reduction might represent, at least partially, impairment of cortical plasticity.

INTRODUCTION: Studies with diffusion tensor imaging (DTI) analysis have produced conflicting information about the involvement of the cerebellar hemispheres in Parkinson's disease (PD). We, thus, used a new approach for the analysis of DTI parameters in order to ascertain the involvement of the cerebellum in PD. METHODS: We performed a fiber tract-based analysis of cerebellar peduncles and cerebellar hemispheres in 16 healthy subjects and in 16 PD patients with more than 5 years duration of disease, using a 3T MRI scanner and a constrained spherical deconvolution (CSD) approach for tractographic reconstructions. In addition, we performed statistical analysis of DTI parameters and fractional anisotropy (FA) XYZ direction samplings. RESULTS: We found a statistically significant decrement of FA values in PD patients compared to controls (p < 0.05). In addition, extrapolating and analyzing FA XYZ direction samplings for each patient and each control, we found that this result was due to a stronger decrement of FA values along the Y axis (antero-posterior direction) (p < 0.01); FA changes along X and Z axes were not statistically significant (p > 0.05). We confirmed also no statistically significant differences of FA and apparent diffusion coefficient (ADC) for cerebellar peduncles in PD patients compared to healthy controls. CONCLUSIONS: The DTI-based cerebellar abnormalities in PD could constitute an advance in the knowledge of this disease. We demonstrated a statistically significant reduction of FA in cerebellar hemispheres of PD patients compared to healthy controls. Our work also demonstrated that the use of more sophisticated approaches in the DTI parameter analysis could potentially have a clinical relevance.

BACKGROUND: In Parkinson's disease (PD), skill retention is poor, even when acquisition rate is generally preserved. Recent work in normal subjects suggests that 5 Hz-repetitive transcranial magnetic stimulation (5Hz-rTMS) may induce phenomena of long-term potentiation at the cortical level. OBJECTIVE/HYPOTHESIS: We thus verified whether, in PD, 5Hz-rTMS enhances retention of a visuo-motor skill that involves the activity of the right posterior parietal cortex. METHODS: A group of patients with PD was tested in two two-day sessions, separated by one week (treatment and placebo sessions). The first day of each session, they learned to adapt their movements to a step-wise 60 degrees visual rotation. Immediately after the task, either real 5Hz-rTMS (treatment) or sham (placebo) stimulation was applied over the right posterior parietal cortex (P6). Retention of this motor skill was tested the following day. RESULTS: In patients with PD, adaptation achieved at the end of training was comparable in the treatment and placebo sessions and was similar to that of a group of age-matched controls. However, retention indices tested on the following day were significantly lower in the placebo compared to the treatment session in which retention indices were restored to the level of the controls. Importantly, reaction and movement time as well as other kinematic measures were the same in the treatment and placebo sessions. CONCLUSION: These results suggest that rTMS applied after the acquisition of a motor skill over specific areas involved in this process might enhance skill retention in PD.

In previous studies of young subjects performing a reaction-time reaching task, we found that faster reaction times are associated with increased suppression of beta power over primary sensorimotor areas just before target presentation. Here we ascertain whether such beta decrease similarly occurs in normally aging subjects and also in patients with Parkinson's disease (PD), where deficits in movement execution and abnormalities of beta power are usually present. We found that in both groups, beta power decreased during the motor task in the electrodes over the two primary sensorimotor areas. However, before target presentation, beta decreases in PD were significantly smaller over the right than over the left areas, while they were symmetrical in controls. In both groups, functional connectivity between the two regions, measured with imaginary coherence, increased before the target appearance; however, in PD, it decreased immediately after, while in controls, it remained elevated throughout motor planning. As in previous studies with young subjects, the degree of beta power before target appearance correlated with reaction time. The values of coherence during motor planning, instead, correlated with movement time, peak velocity and acceleration. We conclude that planning of prompt and fast movements partially depends on coordinated beta activity of both sensorimotor areas, already at the time of target presentation. The delayed onset of beta decreases over the right region observed in PD is possibly related to a decreased functional connectivity between the two areas, and this might account for deficits in force programming, movement duration and velocity modulation.