F61. Oscillatory neuronal activity in the basal ganglia and the ventral thalamus in patients with Parkinson’s disease

Abstract

Parkinson’s disease (PD) is characterized by tremor, rigidity, bradykinesia. According to the classic model of PD, the dopamine deficit in the SNc results in alterations of neuronal activity in the basal ganglia motor circuit, leading to parkinsonian symptoms. The purpose of the study was to characterize oscillatory neurons in the STN, the GPi and the Vop/Vim nuclei in PD patients, the firing rates and proportion of oscillatory neurons in the three nuclei were compared. Twenty-nine patients with PD underwent STN DBS, pallidotomy and thalamotomy were studied. Microelectrode recordings in the STN, GPi and Vop/Vim and EMG on limbs were performed. The interspike intervals were assessed. Spectral analysis was used to evaluate neuronal oscillatory activities. Coherence was performed. Mean spontaneous firing rates (MSFR) and proportions of STN, GPi and Vop/Vim oscillatory neurons were compared. Of 76 STN neurons identified, 39.5% were tremor frequency oscillatory (TFB) neurons and 28.9% were ß frequency oscillatory (ßFB) neurons. Their MSFR was 44.2 ± 7.6 Hz. Of 62 GPi neurons identified, 37.1% were TFB neurons and 27.4% were ßFB oscillatory neurons. Their MSFR was 80.9 ± 9.6 Hz. Of 74 thalamic neurons identified, 45 were Vop neurons and 29 were Vim neurons. Of 45 Vop neurons, 66.7% was TFB oscillatory neurons and 9.0% was ßFB oscillatory neurons. Of 29 Vim neurons, 69% were TFB oscillatory neurons and 13.7% was ßFB oscillatory neurons. Their MSFR was 24.5 ± 4.1 Hz for Vop and 30.8 ± 3.7 Hz for Vim. Further comparisons of MSFR and proportions of TFB, βFB oscillatory neurons in STN, GPi and Vop/Vim found that there were significant other differences among the nuclei. TFB oscillatory neurons predominantly distributed in Vop (66.7%) and Vim (69%) as compared to STN (28.9%) and GPi (27.4%). In contrast, ßFB oscillatory neurons distributed in the STN (28.9%) and GPi (27.4%) as compared to Vop (9%) and Vim (13.7%). There were also significant differences of MSFR of TFB and βFB oscillatory neurons among the four nuclei. The comparisons showed that the highest MSFR was GPi oscillatory neurons (80.9 ± 9.6 Hz), then STN neurons (44.2 ± 7.6 Hz) and Vim neurons (30.8 ± 3.7 Hz), and the lowest rate was Vop neurons (24.5 ± 4.1 Hz). All comparisons were p < 0.05. 1. In comparison to normal animal model, significant increased MSFR of GPi, STN neurons and decreased MSFR of Vop neurons in PD patients supports the prediction of the classic model of PD. 2. The proportions of STN and GPi βFB oscillatory neurons were higher than that of Vop/Vim oscillatory neurons suggesting that dopamine deficits likely increase β frequency oscillations in PD. 3. The TFB oscillatory neurons exist in basal ganglia nuclei STN, GPi and the Vop and Vim as well. Particularly, the highest proportion of TFB oscillatory neuron was observed in Vim suggests that both the basal ganglia and cerebello-thalamic circuits are involved in generation of tremor, cerebello-thalamic circuits seeming to be more important.