Validation and optimisation of a touchscreen progressive ratio test of motivation in male rats

Abstract

RationaleAcross species, effort-related motivation can be assessed by testing behaviour under a progressive ratio (PR) schedule of reinforcement. However, to date, PR tasks for rodents have been available using traditional operant response systems only.ObjectivesTouchscreen operant response systems allow the assessment of behaviour in laboratory rodents, using tasks that share high face validity with the computerised assessments used in humans. Here, we sought to optimise a rat touchscreen variant of PR and validate it by assessing the effects of a number of manipulations known to affect PR performance in non-touchscreen paradigms.MethodsSeparate groups of male Sprague-Dawley rats were trained on PR schedules with either linear (PR4) or exponential (PREXP) schedules of reinforcement. PR performance was assessed in response to manipulations in reward outcome. Animals were tested under conditions of increased reward magnitude and following reward devaluation through a prefeeding procedure. Subsequently, the effects of systemic administration of the dopamine D2/D3 receptor antagonist raclopride and the psychostimulant d-amphetamine were examined as traditional pharmacological methods for manipulating motivation.ResultsRats reinforced under PR4 and PREXP schedules consistently showed differential patterns of response rates within sessions. Furthermore, both PR4 and PREXP schedules were sensitive to suppression by prefeeding or raclopride administration. Performance under both schedules was facilitated by increasing reward magnitude or d-amphetamine administration.ConclusionsTaken together, these findings mirror those observed in lever-based PR paradigms in rats. This study therefore demonstrates the successful validation of the rat touchscreen PR task. This will allow for the assessment of motivation in rats, within the same touchscreen apparatus used for the assessment of complex cognitive processes in this species.

Blockade of muscarinic acetylcholine receptors facilitates motivated behaviour and rescues a model of antipsychotic-induced amotivation

“…While the use of a touchscreen instead of a manipulanda in PR yields reduced overall performance, touchscreen and non-touchscreen PR schedules exhibit similar sensitivity for detecting changes in performance due to pharmacological manipulations or alterations in reinforcer value [38,40]. Furthermore, the present results suggest haloperidol produces a similar reduction in breakpoint (~50%) to previous lever-based reports using the same dose [41].…”

“…While the operant schedules themselves are equivalent, the mode of operant responding (engaging with a physical manipulanda versus a touchscreen stimulus) differs which could in turn impact performance, with increased physical response demands known to reduce operant performance [38,39]. However, in spite of less physical effort being needed to respond to a touchscreen stimulus when compared to a typical manipulanda, measures of touchscreen PR performance are consistently lower relative to lever-based systems [40]. This suggests that some non-physical aspect of effort is greater when PR involves touchscreen responding.…”

Assessment of mGluR5 KO mice under conditions of low stress using a rodent touchscreen apparatus reveals impaired behavioural flexibility driven by perseverative responses

“…The ratio schedule we used here was designed to study motivation [23,32,45]. The canonical interpretation of elevated breakpoints is increased motivation.…”

Design and evaluation of a touchscreen apparatus for operant research with pigeons

“…We should note that touchscreen technology for use with rats and mice is growing in popularity (Dumont et al, 2021), to the extent that commercial versions are sold by Campden Instruments (https://campdeninstruments.com), Lafayette Instruments (https://lafayetteneuroscience.com), and Med Associates (https://www.med-associates.com). The technology is used primarily in assays of rodent cognition by neuroscientists, although some free‐operant work can be found in the literature (e.g., an experiment involving progressive‐ratio schedules by Hailwood et al, 2018). Our system could be readily adapted for use with rats; the principal changes would be lowering the placement of the touchscreen and changing the type of feeder.…”