Premature responses in the five-choice serial reaction time task reflect rodents temporal strategies evidence from no-light and pharmacological challenges.
The five-choice serial reaction time task (5-CSRTT) is regularly used to study attention and impulsivity. In the 5-CSRTT, rodents initiate a trial, then after an inter-trial interval (ITI), a light appears in one of five holes. Responding in the lit vs. unlit hole reflects attention (accuracy), while responding prematurely before a light appears is suggested to reflect impulsivityresponse disinhibition. Comparison of rat and mouse 5-CSRTT performance has raised questions on the validity of premature responses as measuring impulsivityresponse inhibition. To minimize effort, rodents may use a temporal strategy, enabling their timing of the ITI, minimizing the need to attend during this delay. Greater reliance on this strategy could result in premature responses due to guesses if their timing was pooraltered. To assess the degree to which rats andor mice utilize a temporal strategy, we challenged performance using infrequent no-light trials during 5-CSRTT performance. Even when no light appeared when one was expected, rats responded 60 % compared to 40 % in mice, indicating a greater reliance on a temporal strategy by rats than by mice. Consistent with this hypothesis, rats made more premature responses than mice. Additional studies using a temporal discrimination task and a 5-CSRTT variant demonstrated that delta-9-tetrahydrocannabinol, the active ingredient in cannabis, slowed temporal perception and reduced premature responses. These data provide behavioral and pharmacological evidence indicating that premature responses are heavily influenced by temporal perception. Hence, they may reflect an aspect of waiting impulsivity, but not response disinhibition, an important distinction for translational clinical research.