Citric acid water as an alternative to food restriction to motivate task performance in mice during touchscreen testing

Rodent behavioural testing paradigms in touchscreen operant chambers have successfully provided insight into the neural mechanisms underlying various cognitive domains in healthy and disease models. Touchscreen testing has previously required food restriction to sufficiently motivate rodents to complete behavioural tests, limiting the use of interventions, for example diet-based interventions, that alter animals’ motivation for food in experimental design. Here, we explored the safety and efficacy of water manipulation via addition of citric acid in motivating behavioural performance in touchscreen operant chambers 1) in comparison with food restriction and 2) when mice are fed an obesogenic high-fat, high-sugar (HFHS) diet. Water manipulation and food restriction produced similar performance on the progressive ratio task in non-obesogenic, standard-fed mice. However, when water-manipulated mice were fed a HFHS diet they showed deficits in this motivation-sensitive task. Critically, all groups, regardless of restriction type or diet, showed similar learning curves during a pairwise visual discrimination task. Together, these findings demonstrate that water manipulation can safely and effectively motivate mice to perform touchscreen tasks for reward, even when fed a highly satiating HFHS diet, which opens the possibility of using interventions, especially diet-based, in conjunction with touchscreen cognitive testing batteries.