Journal of Neuroscience Methods 109 (2001) 129 – 135 A novel food-delivery device for neurophysiological and neuropsychological studies in monkeys Andrew R. Mitz a, *, Steven A. Boring b , Steven P. Wise a , Mikhail A. Lebedev a a Laboratory of Systems Neuroscience, National Institute of Mental Health, 49 Conent Drie, Building 49, Room B1EE17, Bethesda, MD 20892 -4401, USA b Mechatronic Solutions, Millersille, MD 21108, USA Received 9 April 2001; received in revised form 29 May 2001; accepted 29 May 2001 Abstract Neurophysiological and neuropsychological studies in monkeys sometimes require an automated food-pellet dispenser. Commercially available dispensers typically sequester the pellet until delivery and, once delivered, the pellet’s availability cannot be controlled. The custom-designed dispenser described here overcomes those two limitations. The device is composed of two separate units: a feeder and an electronic controller. The feeder manipulates food pellets with actuators driven by air pressure and delivers them into a serving bowl. The controller’s settings determine whether the monkey can retrieve a pellet from the bowl. If the experiment requires that the pellet be visible and within reach, but unavailable for retrieval, the controller enables a trap-door mechanism at the bottom of the bowl. Any motion near the serving bowl, such as that caused by the approach of a monkey’s hand, will then trigger the opening of the trap door, which causes the pellet to fall into an enclosed pellet collector. This rapid pellet-removal mechanism can also be triggered by other computer-controlled contingencies. Two of these dispensers have been in operation in an applied laboratory setting for over 2 years. Published by Elsevier Science B.V. Keywords: Neurophysiology; Neuropsychology; Primate; Automatic feeder; Pellet dispenser www.elsevier.com/locate/jneumeth 1. Introduction Numerous automatic devices have been developed to deliver food pellets in neurophysiological and neuropsy- chological studies involving monkeys and other animals (Zajac, 1974; MED Associates, Lafayette, IN, USA, Model ENV-203). Existing feeder designs, however, have at least two key limitations: (1) the food only becomes visible and within reach at the end of a behavioral trial; and (2) once the food is delivered, the monkey can always obtain it. The pellet dispenser described here overcomes both of those limitations by giving the experimenter the option of withdrawing the food during reaching, before it can be grasped. This capability allows experimenters to control food availability according to behavioral contexts and rules, rather than merely by the food’s presence or absence. The device described here operated successfully in a recent neurophysiological study of reaching movement and selective spatial attention (Lebedev and Wise, 2001) and may be of value in other neurophysiological and neuropsychological studies, as well. 2. General description The automatic food delivery device has two major components, a mechanical feeder and an electronic controller (Fig. 1). The feeder houses all moving parts for handling food and is the component with which the monkey physically interacts. The controller houses a single-board embedded computer and associated power circuitry for controlling the feeder. A cable shuttles power and control signals between the feeder and the controller, and an air pressure hose runs parallel to the cable in order to supply 2.3 bars of air pressure to the feeder. The air pressure is used to stir food and propel pneumatic cylinders in the feeder under the * Corresponding author. Tel.: +1-301-402-5573; fax: +1-301-402- 5441. E-mail address: arm@nih.gov (A.R. Mitz). 0165-0270/01/$ - see front matter. Published by Elsevier Science B.V. PII:S0165-0270(01)00406-X