We investigated the role of the basal ganglia and thalamus in movement planning and preparation. In patients undergoing deep brain stimulation (DBS) surgery, we recorded simultaneously from scalp electrodes and from DBS electrodes implanted in the subthalamic nucleus (STN) or the pedunculopontine nucleus (PPN) in patients with Parkinson's disease, in the internal globus pallidus (GPi) in patients with dystonia and in the ventrointermediate (VIM) (cerebellar) nucleus of the thalamus in patients with tremor. When patients performed a self-paced wrist extension movement, bilateral premovment potentials or Bereitshaftspotential (BP) were recorded from the STN, PPN, GPi and the VIM about 1.5 to 2 seconds before movement onset, suggesting they are part of a network involved in movement preparation. Before and during self-paced movements, ß oscillations decreased bilaterally which may reflect general motor planning and ? oscillations increased only contralaterally in the GPi, which may reflect specific communications between the cortex and basal ganglia. Dystonia may be associated with excessive 5-18 Hz oscillations. In PD, dopaminergic medications increase the interactions between cortex and PPN. ß oscillations in the PPN increase rather than decrease during the movement planning period, suggesting that it is not antikinetic in the PPN and may explain why therapeutic DBS in the PPN used lower frequencies than in other nuclei in the basal ganglia. In a study in which PD patients received STN DBS at their individualized frequencies based on their local field potential recordings, ß frequency stimulation had no effect but ? frequency stimulation improve PD motor signs, suggesting the ? may be a prokinetic frequency in the STN. In a study that paired transcranial magnetic stimulation (TMS) and DBS, STN DBS was found to increase motor cortex excitability after ~3 ms and ~20 ms, demonstrating that STN DBS can increase motor cortex excitability and is potentially a mechanism of action of DBS. A TMS study also showed that VIM DBS facilitated rather than inhibit transmission in the cerebellothalamocortical pathway, showing that DBS activates rather than inhibit this target area.