SP 3. Direct involvement of the nucleus accumbens in action preparation: Evidence from human intracranial recordings

Deep brain stimulation of the nucleus accumbens influences behaviour, e.g., in obsessive-compulsive disorder. However, the precise role of this region in human decision-making is not well understood. The nucleus accumbens is thought to influence future action selection indirectly, via an evaluation of current action outcomes. Here, we provide electrophysiological evidence for a more direct, “on-line”, behavioural role during action preparation. We recorded local field potentials from the nucleus accumbens in patients with epilepsy undergoing surgery for deep brain stimulation. We found a consistent decrease in the power of beta-oscillations (10–30 Hz) before and around the time of movements. This peri-movement beta-desynchronization was observed in seven of eight patients and was present both before instructed movements in a serial reaction time task as well as before self-paced, deliberate, choices in a decision-making task. A similar beta-decrease over sensorimotor cortex and in the subthalamic nucleus has been directly related to movement preparation and execution. Our results support the idea of a direct role of the human nucleus accumbens in action preparation and execution.