Neuronal activities in the ventrolateral thalamus and basal ganglia in relation to Parkinson's disease

Abstract

To investigate the neuronal activities in the ventrolateral thalamus (VL), internal globus pallidus (GPi), and subthalamic nucleus (STN) in relation to parkinsonian symptoms. Twenty-seven patients with Parkinson's disease, 17 males and 10 females, aged 59 +/- 8, received stereotactic surgical treatment on the VL (n = 10), GPi (n = 10), or STN (n = 7) respectively. Microelectrode recording in the three nuclei and electromyography (EMG) on the limbs contralateral to the surgical side were performed intraoperatively. All patients were evaluated with the unified Parkinson's disease rating scale (UPDRS) in "off" medication state pre-and post-operatively. Single unit analysis and cross-correlation analysis were carried out to explore the relationship among the neuronal activities and limb EMG. One-way ANOVA was performed to study the numbers of neuron in these 3 nuclei in different discharge patterns and the improvement of the 3 main symptoms of Parkinson's disease. Three hundred and sixty-one neurons were obtained from 27 microrecording trajectories (146 for VL, 139 for GPi, and 76 for STN). Three patterns of neuronal activities were identified: tremor-related activities ("tremor cells", n = 159); tonic neuronal activities (n = 134), and irregular neuronal activities (n = 68). The rhythm of the tremor-related activities was correlated with the frequency of limb tremor in VL (r(2) = 0.8, P < 0.01), GPi (r(2) = 0.7, P < 0.01), and STN (r(2) = 0.5, P < 0.01). The average number of cells in each tract of VL, GPi, and STN were 9.0, 4.9, and 3.0 for tremor-related activities (ANOVA, P < 0.05); 4.2, 6.2 and 4.3 for tonic neuronal activities (ANOVA, P > 0.05) and 1.4, 2.8 and 3.7 for irregular neuronal activities (ANOVA, P < 0.05). The UPDRS revealed that VL had the highest effect on tremor improvement (91.7%) as compared to GPi (84.8%) and STN (62.7%), whereas STN and GPi had significant effects on bradykinesia improvement (70.8% and 62.3% respectively) as compared to VL (36.9%). However there was no significant difference in the improvement of rigidity among VL, GPi, and STN (56.2%, 71.3%, and 68.8% respectively, all P > 0.05). Different patterns of neuronal activities in VL, GPi and STN are likely to associate with parkinsonian symptoms. The results are important not only for the target selection, but also for understanding of neurophysiological basis underlying Parkinson's disease.