Deep brain stimulation: is it time to change gears by closing the loop?

Adaptive deep brain stimulation (aDBS) modulates neuronal circuits based on clinically relevant biofeedback signals in real-time. First developed in the mid-2000s, many groups have worked on improving closed-loop DBS technology. The field is now at a point in conducting large-scale randomized clinical trials to translate aDBS into clinical practice. As we move towards implanting brain-computer interfaces in patients, it will be important to understand the technical aspects of aDBS. This review provides a comprehensive overview of the technological building blocks comprising closed-loop systems, feedback variables used to control energy delivery to the brain, and the extent to which DBS parameters can be adapted to improve therapeutic outcomes.