In the basal ganglia circuit, the sub thalamic nuclei provide excitatory input onto the GPi/SNr which will in turn inhibit the thalamic motor nuclei resulting in less excitation of the motor cortex and thus less movement. Parkinson's disease is caused by the loss of dopaminergic input through the direct pathway which normally provides inhibition of the GPi/SNr and subsequent disinhibition of the thalamic motor nuclei leading to the cortex and motor output. Therefore, it is paradoxical that stimulation of the sub thalamic nuclei works because you would think that treatment would lead to facilitation of movement rather than inhibition of movement. Am I correct in this thinking? Some google searching says that we don't understand how DBS works, but if an expert can chime in that would be cool