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. Author manuscript; available in PMC: 2015 Jan 1.
Published in final edited form as: Neurosurg Clin N Am. 2013 Oct 23;25(1):187–204. doi: 10.1016/j.nec.2013.08.006

Figure 1.

Figure 1

General control system diagram representing a conceptualized closed loop neurostimulation system for DBS. In this diagram, the reference signal (* LFP Feature) is the feature extracted from the basal ganglia local field potential. This reference signal* is used to predict a meaningful clinical state of the patient (estimated or predicted clinical state) and these states subsequently direct the selection of desired DBS parameters and appropriate reference values († Desired feature). The controller compares (and calculates an error signal) the reference signal* and value†, and calculates the controlled variable (§ Control signal). The control signal§ and actuator, together with the selection of desired DBS parameters, influence the DBS feedback to the basal ganglia, ultimately impacting the LFP and extracted features*. This impact on the LFP serves as a surrogate marker for the beneficial effect of DBS on the patient, bringing the reference signal* and value† closer together.