A liquid-delivery device that provides precise reward control for neurophysiological and behavioral experiments

Behavioral neurophysiology and other kinds of behavioral research often involve the delivery of liquid rewards to experimental subjects performing some kind of operant task. Available systems use gravity or pumps to deliver these fluids, but such methods are poorly suited to moment-to-moment control of the volume, timing, and type of fluid delivered. The design described here overcomes these limitations using an electronic control unit, a pressurized reservoir unit, and an electronically controlled solenoid. The control unit monitors reservoir pressure and provides precisely timed solenoid activation signals. It also stores calibration tables and does on-the-fly interpolation to support computer-controlled delivery calibrated directly in milliliters. The reservoir provides pressurized liquid to a solenoid mounted near the subject. Multiple solenoids, each supplied by a separate reservoir unit and control unit, can be stacked in close proximity to allow instantaneous selection of which liquid reward is delivered. The precision of droplet delivery was verified by weighing discharged droplets on a commercial analytical balance.