Optimizing reproducibility of operant testing through reinforcer standardization: identification of key nutritional constituents determining reward strength in touchscreensReport as inadecuate




Optimizing reproducibility of operant testing through reinforcer standardization: identification of key nutritional constituents determining reward strength in touchscreens - Download this document for free, or read online. Document in PDF available to download.

Molecular Brain

, 10:31

First Online: 17 July 2017Received: 02 May 2017Accepted: 01 July 2017

Abstract

Reliable and reproducible assessment of animal learning and behavior is a central aim of basic and translational neuroscience research. Recent developments in automated operant chamber technology have led to the possibility of universal standard protocols, in addition to increased translational potential, reliability and accuracy. However, the impact of regional and national differences in the supplies of available reinforcers in this system on behavioural performance and inter-laboratory variability is an unknown and at present uncontrolled variable. Therefore, we aimed to identify which constituents of the reward determines reinforcer strength to enable improved standardization of this parameter across laboratories. Male C57BL-6 mice were examined in the touchscreen-based fixed ratio FR and progressive ratio PR schedules, reinforced with different kinds of milk-based reinforcers to directly compare the incentive values of plain milk PM, high-calorie: high-fat-low-sugar, strawberry-flavored milk SM, high-calorie: low-fat-high-sugar, and semi-skimmed low-fat milk LM, low-calorie: low-fat-low-sugar on the basis of differences in caloric content, sugar-fat content, and flavor. Use of a higher caloric content reward was effective in increasing operant training acquisition rate. Total trial number completed in FR and breakpoint in PR were higher using the two isocaloric milk products PM and SM than the lower caloric LM, with comparable outcomes between PM and SM conditions, suggesting that total caloric content determines reward strength. Analysis of within-session changes in response rate revealed that overall outputs in FR and PR primarily depend on the response rate at the initial phase of a session, which itself was dependent on reinforcer caloric content. Interestingly, the rate of satiation, indicated by decay in response rate within a FR session, was highest when reinforced with SM, suggesting a rapid satiating effect of sugar. The key contribution of reward caloric content to operant performance was confirmed in a multi-laboratory study using the touchscreen 5-choice serial reaction time task 5-CSRTT reinforced by two isocaloric milk-based liquid rewards with different countries of origin, which yielded consistent performance parameters across sites. Our results indicate that milk-based liquid reinforcer standardization can be facilitated by matching caloric content across laboratories despite regional or national differences in other non-caloric aspects of the reinforcers.

KeywordsReinforcer Operant behavior Calories Touchscreen chamber Standardization Abbreviations5-CSRTT5-choice serial reaction time task

ANOVAanalysis of variance

FRfixed ratio

IRinfrared

ITIinter-trial interval

LEDlight-emitting diode

LMlow-fat milk

PMplain milk

PRprogressive ratio

SMstrawberry-flavored milk

SSSeoul Strawberry Milk

Electronic supplementary materialThe online version of this article doi:10.1186-s13041-017-0312-0 contains supplementary material, which is available to authorized users.

Download fulltext PDF



Author: Eun Woo Kim - Benjamin U. Phillips - Christopher J. Heath - So Yeon Cho - Hyunjeong Kim - Jemeen Sreedharan - Ho-Taek S

Source: https://link.springer.com/







Related documents