Deep brain stimulation: anatomical, physiological, and computational mechanisms

Basal ganglia network dynamics and function: Role of direct, indirect and hyper-direct pathways in action selection

Basal ganglia (BG) are a widely recognized neural basis for action selection, but its decision-making mechanism is still a difficult problem for researchers. Therefore, we constructed a spiking neural network inspired by the BG anatomical data. Simulation experiments were based on the principle of dis-inhibition and our functional hypothesis within the BG: the direct pathway, the indirect pathway, and the hyper-direct pathway of the BG jointly implement the initiation execution and termination of motor programs. Firstly, we studied the dynamic process of action selection with the network, which contained intra-group competition and inter-group competition. Secondly, we focused on the effects of the stimulus intensity and the proportion of excitation and inhibition on the GPi/SNr. The results suggested that inhibition and excitation shape action selection. They also explained why the firing rate of GPi/SNr did not continue to increase in the action-selection experiment. Finally, we discussed the experimental results with the functional hypothesis. Uniquely, this paper summarized the decision-making neural mechanism of action selection based on the direct pathway, the indirect pathway, and the hyper-direct pathway within BG.

Bilateral deep brain stimulation of the subthalamic nucleus in primary Meige syndrome

OBJECTIVE

Subthalamic nucleus deep brain stimulation has been shown to be effective in reducing symptoms of primary Meige syndrome. However, assessments of its efficacy and safety have been limited to several case reports and small studies.

METHODS

The authors performed a retrospective study to assess the efficacy and safety of bilateral subthalamic nucleus stimulation in 15 patients with primary Meige syndrome who responded poorly to medical treatments or botulinum toxin injections. Using the movement and disability subscores of the Burke-Fahn-Marsden Dystonia Rating Scale, the authors evaluated the severity of patients’ dystonia and related before surgery and at final follow-up during neurostimulation. The movement scale was assessed based on preoperative and postoperative video documentation by an independent rater who was unaware of each patient’s neurostimulation status. Quality of life was assessed with the Medical Outcomes Study 36-Item Short-Form General Health Survey.

RESULTS

The dystonia movement subscores in 14 consecutive patients improved from 19.3 ± 7.6 (mean ± standard deviation) before surgery to 5.5 ± 4.5 at final follow-up (28.5 ± 16.5 months), with a mean improvement of 74% (p < 0.05). The disability subscore improved from 15.6 ± 4.9 before surgery to 6.1 ± 3.5 at final follow-up (p < 0.05). In addition, the postoperative SF-36 scores increased markedly over those at baseline. The authors also found that bilateral stimulation of the subthalamic nucleus immediately improved patient symptoms after stimulation and required lower stimulation parameters than those needed for pallidal deep brain stimulation for primary Meige syndrome. Four adverse events occurred in 3 patients; all of these events resolved without permanent sequelae.

CONCLUSIONS

These findings provide further evidence to support the long-term efficacy and safety of subthalamic nucleus stimulation as an alternative treatment for patients with medically intractable Meige syndrome.