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 zebrafish. The five aperture and food hopper inserts are used to create the experimental environment (see image A below). 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, see image B below). Responses are detected when a fish enters these zones (see image C below).
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.
- Habituation/Autoshaping: Subjects are concurrently acclimated to the testing tank and autoshaped to the food hopper. Individual fish are placed in a Zantiks AD tank and shaped to swim into the food delivery area when the hopper light is illuminated. Following a 60 sec intertrial interval (ITI) the food hopper light illuminates and food is delivered. This step allows the fish to habituate to the noise of food delivery and to the testing environment, as well as learn to enter the food delivery area.
- Stimulus Light Training: Fish are next trained to trigger any of the five stimulus lights as a method of orientation to the stimuli. All five stimulus lights are simultaneously illuminated in the five apertures at the back of the tank. The fish needs to enter any of the apertures in order for the food hopper light to illuminate and food reward to be delivered. If they do not respond in the limited hold (LH; 30 sec), no food reward is delivered. A new trial begins following a 20 sec ITI.
- Initiator Light Training: Fish learn to trigger the initiator light (illuminated for 30 secs) to begin a trial. Triggering the initiator light, illuminates the food hopper light and food reward delivery. This is followed by the fish learning to trigger the initiator light (beginning the trial), followed by triggering any of the five illuminated stimulus lights at the end of the tank to receive food reward.
- Stimulus Light Discrimination: The fish now initiates the trial, which illuminates a single stimulus light. Stimulus lights are presented in random order. The fish must enter the illuminated aperture during the LH to receive the food reward.
- 5-CSRTT: The final step is conducted similarly to the 4th, with the addition to a n-sec delay. The fish initiates the trial, and needs to withhold from responding during the set ITI. One of the five apertures is then briefly illuminated and the fish must now respond within the LH in order to receive food reward.
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.