a Diagram showing the “on-off keying” control scheme used by Bozorgzadeh B, Schuweiler DR, Bobak MJ, et al.  as part of their control system. Adapted from: Bozorgzadeh B, Schuweiler DR, Bobak MJ, et al. . b Model of the real-time closed-loop system developed by researchers at the Mayo Clinic in order to control dopamine response within the brain. Adapted from: Grahn PJ, Mallory GW, Khurram OU, et al.