Figure 1. Invasive microelectrode recordings and slot machine task.

(A) Electrode placement during DBS surgery for Parkinson’s Disease patients. Microelectrodes were parked past the ventral border of the subthalamic nucleus, and single-unit recordings taken from the substantia nigra. (B) Two-armed bandit slot machine behavioral task. Patients choose between two slot machines with 80%/20% and 20%/80% probability of a better/worse outcome. Patients play 3x35-trial blocks in pseudo-randomized order, with either +$10/0 (reward block), +$10/−$10 (mixed block) or −$10/$0 (punishment block) outcomes. The contingencies switched twice between slot machines during each block. The patients are shown the slot machines until they make a choice. After a machine is chosen, it spins for 3 seconds until landing on the outcome, which stays on the screen for 1second before the slot machines reset and a new trial starts. (C) Microelectrode data (left) is high pass filtered, spike sorted to identify individual units (middle) and manually processed to discard or merge clusters into the final units per recording (right).