Objective: To explore whether patterns of synchronized subthalamic oscillatory neurons are involved in generating parkinsonian subtypes.

Background: The pathophysiology for parkinsonian subtypes is unclear. Both oscillation and synchrony among the basal ganglia  is believed to contribute to motor symptoms. A recent study [1] showed that there are tremor frequency and β frequency oscillatory neurons synchronized with their local background oscillation in the subthalamic nucleus (STN). Whether these two patterns are specifically related to parkinsonian subtypes is unknown.

Method: Thirty patients with PD who underwent STN deep brain stimulation (DBS)  were included. Thirteen patients were classified as AR type, 8 patients were classified as tremor type, and 9 patients were classified as mixed type. Microelectrode recording was performed in the STN and EMG was simultaneously recorded. Single unit and spectral analyses were performed. Neuronal background activities were also evaluated. Coherence analysis was performed to explore relationship between subthalamic oscillatory neurons, their background oscillatory activity and limb EMG activity. One-way ANOVA and Chi-square were used to compare the differences between the three subtypes.

Results: Of 143 neurons identified in the AR type, 35% were β frequency oscillatory neurons and 0.7% were tremor frequency oscillatory neurons. Of 79 neurons identified in the tremor type, 11.4% were β oscillatory neurons and 22.8% were tremor oscillatory neurons. Of 96 neurons identified in the mixed type, 21.9% were β oscillatory neurons and 17.7% were tremor oscillatory neurons. Coherence revealed that 95% β oscillatory neurons were coherent with their background oscillatory activity, and 83% tremor frequency oscillatory neurons were coherent with their background oscillation. Additional coherence analysis showed that 13% synchronized β oscillatory neurons were coherent with limb EMG in AR type, but there was no coherence in tremor and mixed types. In contrast, 22%  synchronized tremor frequency oscillatory neurons were coherent with limb tremor in tremor type, but there was no coherence in AR and mixed types.

Conclusion: The synchronized β and tremor frequency oscillatory neurons were directly coherent with limb rigidity in AR type and tremor in tremor type, respectively, suggesting that the two patterns of synchronized oscillatory neurons are involved in producing motor subtypes.

References: [1].Moran A, Bergman H, Israel Z, Bar-Gad I. Subthalamic nucleus functional organization revealed by parkinsonian neuronal oscillations and synchrony [J]. Brain : a journal of neurology, 2008, 131(Pt 12): 3395-3409.
[2].Zaidel A, Arkadir D, Israel Z, Bergman H. Akineto-rigid vs. tremor syndromes in Parkinsonism [J]. Current opinion in neurology, 2009, 22(4): 387-393.
[3] Oswal A. Brown P. Litvak V. Synchronized neural oscillations and the pathophysiology of Parkinson’s disease. Current opinion in neurology, 2013, 26(6)::663-670.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/patterns-of-subthalamic-synchronized-oscillatory-activity-associated-with-parkinsonian-subtypes/