Objective: To characterize the firing rate and pattern of oscillatory neurons in basal ganglia and thalamus in patients with Parkinson’s disease (PD).

Background: The cardinal features of PD are bradykinesia, rigidity and resting tremor. Abnormal activity in basal ganglia has been predicted to underlie the mechanism of parkinsonism. Although a large number of studies suggests that alteration in neuronal activity in basal ganglia is associated with parkinsonian symptoms, the mechanism of parkinsonism remains unclear.

Methods: 29 PD patients with PD were studied. Microelectrode recordings in the STN (n=16), GPi (n=9) and the Vop/Vim were performed. EMG activity from the contralateral limbs was recorded. Single unit analysis and interspike interval measurements were carried out. Spectral and coherence analysis were performed to study oscillatory neurons in relation to EMG activity. Mean spontaneous firing rate (MSFR) of oscillatory neurons were calculated. Analysis of variance (ANOVA) and Chi-square test was performed.

Results: Of 76 STN neurons, 39.5% were tremor frequency oscillatory neurons (TFB) and 28.9% were β frequency oscillatory neurons (βFB). The MSFR was 44.2 ± 7.6 Hz. Of 62 GPi neurons, 37.1% were TFB oscillatory neurons and 27.4% were βFB oscillatory neurons. The MSFR was 80.9 ± 9.6 Hz. Of 45 Vop neurons, 66.7% were TFB oscillatory neurons and 9.0% were βFB oscillatory neurons. The MSFR was 24.5 ± 4.1 Hz. Of 29 Vim oscillatory neurons, 69% were TFB oscillatory neurons and 13.7% were βFB oscillatory neurons. The MSFR was 30.8 ±3.7 Hz. Further comparison indicated that proportion of βFB oscillatory neurons in STN and GPi was significantly higher than that of similar neurons in Vop and Vim. Conversely, the proportion of TFB oscillatory neurons in Vim and Vop was significant higher than that of STN and GPi. ANOVA indicated significant differences of MSFR of oscillatory neurons in four nuclei. The highest MSFR was GPi oscillatory neurons whereas the lowest MSFR was Vop oscillatory neurons.

Conclusions: The firing rate and pattern of oscillatory neurons in basal ganglia structures play an important role in generation of parkinsonian motor symptoms. β oscillatory activity, thought to be antikinetic, is more prominent in the basal ganglia than in the thalamus. While both basal ganglia and thalamus have tremor activity, the thalamus appears to play a more important role in tremor production.

References: 1. DeLong MR (1990) Primate models of movement disorders of basal ganglia origin. Trends Neurosci 13: 281-285. 2. Alteration in neuronal activity basal ganglia-thalamocorticalcircuits in the parkinsonian state Frontiers in Neuroanatomy 20159(5):1-20.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/properties-of-oscillatory-neuronal-activity-in-the-basal-ganglia-and-thalamus-in-patients-with-parkinsons-disease/