Fig 1. Schematic of the automated, experimenter-free operant system.

The rats are permanently housed in two connected home cages. They enter the operant touchscreen chamber through an automated animal sorter (Sorter). The sorter has two guillotine gates (Gate 1 and Gate 2) and three transponder readers (R1, R2 and R3). The individual transponder chip of each rat is identified by transponder readers. The operant touchscreen chamber contains a reward tray and pellet dispenser (outside the chamber), house light, speaker and operant touchscreen. Rats can access the chamber through a 6.5 cm hole to which the sorter is connected. Not to scale; dimensions are provided.