Changes in corticomotor pathway excitability after exercise training in Parkinson's disease

Investigation of the changes in the presynaptic inhibition in association with the subthalamic nucleus stimulation in Parkinson's disease

BACKGROUND AND PURPOSE

Presynaptic inhibition (PSI) is a critical spinal inhibitory mechanism for modulating muscle coordination by adjusting both supraspinal motor commands and sensory feedback at the spinal level. The literature data regarding the role of PSI in the efficiency of STN-DBS therapy in Parkinson's disease (PD) are limited. We aimed to investigate the possible alteration in this pathway in association with the STN stimulation (STIM) within the very early period after the STIM is off.

METHODS

We performed the H-reflex investigation on 8 PD subjects with STN-DBS who applied to our polyclinic for routine clinical evaluations. The investigations were initially performed at the STIM-on period and repeated after the STIM set is off for 5 min. A within-subjects ANOVA was used to test for a significant difference between the STIM-on and -off states for the variables of (repeated measures) H-latency, H amplitude, M amplitude, H/M amplitude, H threshold, and M threshold.

RESULTS

The results of the analyses did not reveal marked changes in the variables of the H-reflex between the STIM-on and -off states.

CONCLUSION

PSI do not alter in the very early period after the STIM is off. Taken together with the related literature data and our study results, it can be hypothesized that the PSI might involve in the DBS efficiency in the later phase of the STIM as a compensatory mechanism. Further prospective studies including a larger number of patients with serial electrophysiological recordings to investigate the temporal course of the underlying dynamics are required to clarify these discussions.

Exercise Improves Movement by Regulating the Plasticity of Cortical Function in Hemiparkinsonian Rats

Aberrant cortical spike-local field potential (LFP) coupling leads to abnormal basal ganglia activity, disruption of cortical function, and impaired movement in Parkinson's disease (PD). Here, the primary motor cortex mediated plasticity mechanism underlying behavioral improvement by exercise intervention was investigated. Exercise alleviates motor dysfunction and induces neuroplasticity in PD. In this study, Sprague-Dawley (SD) rats were injected with 6-hydroxydopamine (6-OHDA) to induce unilateral nigrostriatal dopamine depletion. Two weeks later, a 4-week exercise intervention was initiated in the PD + exercise (Ex) group. Multichannel recording technology recorded spikes and LFPs in rat motor cortices, and balanced ability tests evaluated behavioral performance. The balanced ability test showed that the total crossing time/front leg error/input latency time was significantly lower in PD + Ex rats than in PD rats (P < 0.05). Scalograms and LFP power spectra indicated increased beta-range LFP power in lesioned hemispheres, with exercise reducing LFP power spectral density. Spike-triggered LFP waveform averages showed strong phase-locking in PD motor cortex cells, and exercise reduced spike-LFP synchronization. Our results suggest that exercise can suppress overexcitability of LFPs and minimize spike-LFP synchronization in the motor cortex, leading to motor-improving effects in PD.