Basic Neuroscience
A novel touch-sensitive apparatus for behavioral studies in unrestrained squirrel monkeys

https://doi.org/10.1016/j.jneumeth.2012.06.028Get rights and content

Abstract

Despite the increasing sophistication and affordability of touch-sensitive technology, its use in the behavioral sciences has been limited. The present paper describes the design and empirical validation of a novel touch-sensitive operant conditioning chamber for use with unrestrained squirrel monkeys. In addition, results from a variant of a commonly employed animal model of learning, the repeated acquisition task, demonstrate the effectiveness of this chamber in programming an assay of complex behavior. Finally, results from a study with Δ9-tetrahydrocannabinol, the active ingredient in marijuana, show that its effects in this novel touchscreen chamber were consistent with its dose-related effects on learning using more conventional approaches. Overall, these studies indicate the touchscreen apparatus provides effective means for programming complex behavioral tasks to assess the effects of pharmacological agents on cognitive function.

Highlights

► Touch-sensitive technology use in the behavioral sciences has been limited. ► Describes the design and empirical validation of a novel touch-sensitive operant chamber for use with squirrel monkeys. ► Results demonstrate the effectiveness of this chamber in programming an assay of complex behavior. ► Results with Δ9-tetrahydrocannabinol show consistent dose-related effects on learning with more conventional approaches. ► Touchscreen provides effective means for programming complex behavioral tasks to assess the effects of drugs on cognition.

Introduction

In recent years touch-sensitive technology, which permits the use of computer-generated stimuli, has become both more sophisticated and affordable. Despite this, its use in the behavioral sciences employing operant methodology has developed slowly. As interest increases in studies of complex behavior, including higher-order cognitive function in laboratory animals, especially in nonhuman primates (NHP), researchers may benefit from the relatively unlimited variety of complex stimuli as well as the variability in stimulus position afforded by touchscreen technology that are not possible with standard stimulus lights and levers.

Several recent studies have used touch-sensitive technology with NHP but, typically, with a portable apparatus that is attached to the homecage (e.g., Judge et al., 2011, Rodriguez et al., 2011, Takemoto et al., 2011). These studies report orderly data but also illustrate some limitations. For example, conducting studies in the homecage environment may be problematic depending on species. When describing why experimental sessions were shorter for squirrel monkeys than rhesus monkeys, Judge et al. (2011) stated, “some squirrel monkey subjects would not maintain attention to the task for longer testing sessions” (p. 59). This limitation may stem from the less-controlled and often noisy environment of NHP colonies. Indeed, advantages of isolated sound- and light-attenuating chambers were noted early on in the behavioral literature (e.g., Skinner, 1956) and remain an important feature of operant conditioning methodology. With this in mind, the purpose of the present studies was to, first, construct and empirical validate an isolated touch-sensitive chamber for squirrel monkeys. Squirrel monkeys (Saimiri sciureus) have served as subjects in experimental psychology and behavioral pharmacology for over five decades and continue to provide extremely useful information regarding the behavioral effects of psychoactive drugs (e.g., Desai et al., 2007, Justinova et al., 2005, Kelleher et al., 1963, Kelleher and Morse, 1968, Spealman, 1979). Their small size (usually 750–1100 g), lifespan (approximately 20 years under laboratory conditions), and new world origins (free of hepatitis A and B, herpes B), make them a relatively convenient and safe nonhuman primate experimental subject (see Rosenblum and Cooper, 1968). Next, the utility of the chamber was assessed with a variant of a common cognitive task. Finally, pharmacological sensitivity under these novel testing conditions was assessed with Δ9-tetrahydrocannabinol (Δ9-THC), a drug that has been shown to have dose-related effects on hippocampal-based learning and memory in NHP (e.g., Hampson and Deadwyler, 1999, Hampson et al., 2011).

Section snippets

Experiment 1

The purpose of Experiment 1 was to empirically validate the novel apparatus by first using a stimulus fading procedure to train touch responses and then evaluating the fidelity of the screen as a response transducer by assessing relative response rates under fixed-ratio (FR) schedules of reinforcement in different areas of the screen.

Experiment 2

The results from Experiment 1 validated the first of two primary characteristics of touchscreen technology in operant conditioning chambers, namely that all areas of the screen can be used by the subject with comparable efficiency, thus providing a large variety of possible stimulus position arrangements. The second characteristic of this technology involves the near-limitless variety of visual stimuli that can be presented to the subject. The purpose of Experiment 2 was to investigate

Experiment 3

Experiment 3 employed Δ9-THC, the primary psychoactive ingredient in marijuana, and most commonly abused illegal drug in the United States (SAMHSA, 2011), to determine whether the novel conditions of the experimental chamber and learning task were suitable for pharmacological studies. Δ9-THC, a CB1 partial agonist, binds to CNS CB1 receptors in brain regions that are implicated in learning processes, including basal ganglia, cerebellum, and hippocampus (Glass et al., 1997, Hampson and

Discussion

The present results validate our novel isolated touch-sensitive chamber for squirrel monkeys as an experimentally robust means for studying complex behavior. The touchscreen appears to be an effective response transducer, and is capable of exposing subjects to a near-limitless quantity of complex stimuli in a variety of stimulus-position arrangements. The chamber/task conditions were also suitable for determining the dose-related effects of Δ9-THC, a compound well known to produce effects on

Acknowledgements

The authors thank Michael Z. Leonard for assistance conducting this study.

This research was supported by grants DA023142 and DA007252 from the National Institute on Drug Abuse.

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