Tim takes TWiN through two studies on the role of dopamine: that syllables are natural units of spontaneous behavior used by the brain to structure action, and that mesolimbic dopamine release conveys causal associations but not reward prediction errors, thereby challenging the dominant theory of reward learning.

Jason and Tim review the use of an implanted chronic deep brain sensing and stimulation device to carry out biomarker-driven closed-loop therapy that resulted in a rapid and sustained improvement in depression.