The 5-choice serial reaction time task, 5-CSRTT, is a continuous performance test used to assess attentional processes and impulse control.
During this task, an animal is required to respond to the presence of a briefly presented stimulus (usually a light) in one of 5 locations at the rear of the testing chamber. Aspects of attention and executive performance can be investigated through manipulation of stimulus light exposure length and the addition of distractors. While, impulsivity can be measured through the animals’ premature or anticipatory responding (i.e., responding prior to the stimulus light onset).
The Zantiks AD unit is used for the 5-CSRTT in adult zebrafish. The five aperture and food hopper inserts are used to create the experimental environment. The food hopper insert is designed to form an area for the fish to enter and collect food reward, without the food escaping into the remainder of the tank, as well as an entry point for initiating trials. The five aperture insert creates five distant entry points at the opposite end of the tank from food delivery. The five holes act in a similar fashion to the five nose poke holes in a rodent version of the task.
White light is typically used as stimuli for this experiment, which is presented from the integrated screen below the testing tank. Target zones are assigned to specific locations within the tank (e.g., the five stimulus light locations. Responses are detected when a fish enters these zones.
The 5-Choice serial reaction time task inserts in the Zantiks AD unit:
C) Video recorded during the running of the experiment. A fish is tracked, as indicated by the white cross. Stimuli are not visible on the live tracking image due to the infra-red tracking, so the stimuli are denoted on the image with coloured boxes.
5-CSRTT training is divided into five distinct training stages. All sessions are typically run for 30 minutes or 30 trials, whichever comes first.
- Habituation (stage 1): All lights are illuminated (initiator and 5 stimulus lights) for 50 sec. Entry into any illuminated area is reinforced with a small food reward. This is followed by a 10 sec intertrial interval (ITI) during which no lights are illuminated. A ‘correct’ response is recorded as the zebrafish swimming into the area when illuminated and returning to the feed delivery area. A fish moved to the next stage of training when it completes ≥ 50% trials correctly.
- Initiator training (stage 2): Only the initiator light is illuminated for 50 sec (10 sec ITI). A ‘correct’ response is recorded as the zebrafish swimming into the initiator area when illuminated. The correct response is reinforced with a food reward. A fish moved to the next stage of training when it completes ≥ 50% trials correctly in two sessions consecutively.
- Stimulus light training (stage 3): Fish are required to swim into the initiator light to start the trial. In a trial, all five of the stimulus lights are illuminated immediately for 50 sec (10 sec ITI). If the fish swims into any of the stimulus light areas, it is reinforced with food reward. A fish moved to the next stage of training when it completes ≥ 50% trials correctly in two sessions consecutively.
- 5-CSRTT/No-Delay (stage 4): Fish are required to swim into the initiator light to start the trial. In a trial, one of the five of the stimulus lights is illuminated immediately for 50 sec (10 sec ITI). If the fish swims into the illuminated area it is reinforced with food reward. In this stage, the requirement for correct responses changes. A correct response is the total correct responses as a function of total trials in which the fish made a choice (i.e., accuracy= TotalCORRECT / (TotalCORRECT + TotalINCORRECT)). A fish moved to the final stage of training when it completes ≥ 80% trials correctly in two sessions consecutively. They also must complete a minimum of 10 of the 30 total trials in a session during each of the two ≥ 80% correct sessions.
- 5-CSRTT/Delay and drug treatment (stage 5): Fish are required to swim into the initiator light to start the trial. In a trial, one of the five of the stimulus lights is illuminated immediately for 50 sec (10 sec ITI) following a variable interval (VI) delay of mean = 10 sec. If the fish swims into the illuminated stimulus light, it is reinforced with food reward. As testing is now for impulsivity, as well as correct responses, premature responses are recorded (i.e., anticipatory responding= TotalPREMATURE / (TotalPREMATURE + TotalCORRECT + TotalINCORRECT)).
There are several parameters that are commonly used in the 5-choice serial reaction time tasks including: correct responses (responses to correct stimulus light) and incorrect responses (responses to the incorrect location), omissions (not responding following stimulus presentation) and premature responses (responding to any of the apertures prior to stimulus presentation). Zantiks AD units can be scripted to automatically process these variables.
- Accuracy: CORRECT/(CORRECT + INCORRECT)*100 – a measure of selective attention
- Percent Correct: CORRECT / (TOTAL NUMBER OF TRIALS)*100 – a measure of overall performance
- Percent Omission: OMISSIONS / (OMISSIONS + CORRECT + INCORRECT)*100 – a measure of sustained attention/motivation
- Anticipatory responses: EARLY/(EARLY + CORRECT + INCORRECT)*100 – a measure of impulsivity/response inhibition
The number of sessions needed to reach criterion for a stage of training in the 5-CSRTT can be analysed by repeated measures ANOVA (GLM-RM) with group (e.g., drug dose, genotype) (between) and session (within) factors.