This protocol provides a better animal model for investigating the effects of the mere presence of a confederate animal on motor performance. This protocol enables us to evaluate the effects of confederate animals on both the speed and accuracy of motor performance of rats in a single experiment. Before beginning the experiments, mount a 400-hertz 75-decibel buzzer on the partition of the apparatus.
And set up a pellet dispenser for serving a 45-milligram reward pellet into a food receptacle on the subject side of the box. On the confederate side, insert a transparent wall in front of the partition wall that prohibits the confederate rat from accessing the lever, and tie the proper length of gut to the lever. Connect an appropriate graphic user interface to the apparatus to control the guillotine doors, buzzer, and pellet dispenser, and to obtain the value from the infrared sensors and the switch of the dispenser.
Then set up a 25-liter air compressor for operating the air cylinder and opening the guillotine door. And place a video camera near the partition of the outside of the apparatus. For lever-pull action training, place a naive male albino 300-to 350-gram Wistar rat on the start area, and present the buzzer tone for five seconds before opening the door.
When the subject rat pulls down the lever, deliver a food pellet, and pull up the lever using the gut tied to the lever. After the rat has pulled down the lever for the appropriate number of times for the stage of the phase of the experiment and consumed all of the reward pellets, close the door and move the rat to the start area. After an inter-trial interval of 20 seconds, present the buzzer again, and allow the rat to access the lever as just demonstrated.
For run-and-pull sequence training, after the first time the rat pulls down the lever and consumes a reward pellet, immediately close the door and return the rat to the start area as demonstrated. After an inter-trial interval of 20 seconds, start the next trial, finishing the daily session when each rat has earned 30 pellets. At the completion of both sets of training sessions, conduct a single session that is identical to the sessions in the training phase for the run-and-pull sequence.
But this time, place one reward pellet on the food receptacle on the confederate side of the apparatus. In pair sessions, place a confederate rat in the runway of the confederate side of the apparatus, and give the confederate rat a reward pellet during the inter-trial interval of the subject rat to keep the confederate rat near the partition. To assess the index of the performance accuracy of each session, use an appropriate video playback software program to perform a frame-by-frame analysis of the video recordings of the lever-pull movement of the animals during each session.
Use the analysis to determine whether or not the pulling movement of the trial was the first hit by visual observation of the rat during the experiment. Then calculate the first-hit rate for each subject rat as the proportion of first-hit trials to all trials in each session or in each phase of the test phase. To assess the indices of the performance speed, calculate the time from the door opening to the arrival of the rat at the first sensor, the time from the arrival of the rat at the first sensor to the arrival at the second sensor, and the time from the arrival at the second sensor to the time point when the switch of the dispenser is pressed.
In this representative experiment, the mean first-hit rate increased gradually during the first half of the training phase, before stopping at about 85%Similarly, the indices of performance speed decreased continuously during the first four sessions, with all of the values stabilizing at about 600 milliseconds during the latter four sessions. Evaluation of the index of performance accuracy reveals that the first-hit rate in pair phases for both the first and second phase experiments was lower than in the single phases. Additional analysis of the indices of performance speed show that the start latency in pair phases was shorter than in single phases, and that a difference was observed between the conditions for the lever-pull latency.
No significant effect was determined for the running time. With minor modifications, this protocol can be applied to investigate the effects of co-action or social facilitation with mirrors or other social situations that have been studied in humans. This protocol can be used for neural or comparative cognitive studies, because the tendency for performance accuracy in rodents in different social situations have not yet been conducted.
