The overall goal of this procedure is to train and test rats on the five choice serial reaction time task, or five CS RTTA task of spacial attention and impulse control. This is accomplished by first training rats to retrieve sugar pellets from a food magazine. In the second step, the rats are trained to nose poke into an illuminated aperture to retrieve a sugar pellet reward from the magazine.
Next, the difficulty of the task is increased by shortening the duration of the stimulus and increasing the time between the trials. Ultimately, changes in the performance of specific task parameters can be interpreted to determine if attention or impulse control is affected by a particular manipulation. The main advantage of this task is that it can be combined with neurochemical genetic or neuro anatomic manipulations to gain a better understanding of how these factors are involved in the regulation of attention and impulse control.
For the purposes of demonstration, we are leaving the doors to the sound attenuating chamber open. When you train your rats, you'll want to close the doors. The five CS RTT apparatus is housed within a ventilated sound attenuated operant conditioning chamber with two plexiglass sidewalls and a stainless steel grid floor.
The aluminum front wall is rounded and contains five nose poke apertures, each equipped with a light emitting DDE and an infrared sensor capable of detecting the insertion of the rat's nose. The aluminum back wall contains the food magazine, which is connected to a pellet dispenser and is equipped with an infrared sensor and a small incandescent light. The incandescent house light, a fixed near the top of the back wall is capable of illuminating the entire chamber.
And the five CS RTT apparatus is connected to a computer that controls the operant chamber and collects the data Training on the five choice serial reaction time task occurs over several stages and takes several weeks as outlined in the table. Train the animals at a standard time each day for a minimum of five days a week. In the same operant chamber Before the first session, introduce 45 milligrams of sugar pellets to the rats in their home cage.
To minimize neo phobia and to ensure the animals will retrieve sugar pellets from the food magazine. To initiate the training first place the rats in the operant chamber with the fans on and the aperture holes occluded. Allow the rats to habituate to the chamber for five minutes.
Next, deliver sugar pellets to the magazine according to the appropriate experimental schedule at the end of a daily magazine training session. Note whether the sugar pellets have been consumed. Once the animals have mastered pellet retrieval.
Begin the five CS RTT training. First, allow the animal to habituate to the chamber with the fans on as just demonstrated. Then illuminate the magazine light and deliver one sugar pellet.
On the first few days of training, it might be necessary to encourage nose poking in the apertures by placing sugar pellets into each of the holes. The first trial starts when appellate is retrieved. At the beginning of each trial, there is an inter trial interval during which only the house light is illuminated.
At the end of the inter trial interval, one of the aperture lights is pseudo randomly illuminated for the prescribed stimulus period, and the rat is allowed to respond for the duration of the limited hold correct. Trial responses of nose pokes into the illuminated aperture are rewarded with the delivery of one food pellet and illumination of the magazine. Upon pellet retrieval extinguish the magazine light initiating the next trial.
Incorrect trial responses of nose poke into unlit apertures and omissions. That is failures to respond during the limited hold are punished by extinguishing the house light for a timeout. The end of the timeout and the start of the next trial are signaled by illuminating the house.Light.
Responses during the inter trial interval are scored as premature responses and are punished with a timeout period and each training session after 90 trials or 30 minutes, whichever comes first. It takes several weeks to make it through the various training stages. The rats only graduate from one training stage to the next if they reach the criterion performance for that training stage.
Testing with test day challenges can only commence once the animals have reached a stable performance. On the final stage of training, use test day challenges as outlined in the table. To further probe the animal's behavior, calculate the rat's baseline performance by averaging the performance across the last three to five sessions.
One approach to varying the attentional demands of the task is to alter the duration of the stimulus. As the stimulus duration decreases, the percent accuracy decreases and the percent omissions increase. Thus shorter stimulus durations increase the attentional demands of the task, and longer stimulus durations decrease the attentional demands of the task.
Another approach is to probe the animal's performance. By changing the inter trial interval, decreasing the inter trial interval decreases the percent accuracy and increases the percent omissions because of the short duration of the inter trial interval. The number of premature responses also tends to decrease as illustrated in these graphs.
The response inhibition or impulsivity can also be systematically challenged in the five CS RTT by increasing the duration of the inter trial interval. Increasing the inter trial interval reliably increases the number of premature responses committed without having systematic effects on other performance measures. These data illustrate that blocking cortical GABA synthesis with intra prefrontal cortex infusions of the glutamic acid decarboxylase inhibitor L allo glycine increases omissions but does not affect the percent accuracy in a standard five CS RTT in order to gain a better understanding of factors that contribute to increased omissions.
In this experiment, for example, the animal's performance was first assessed on a more difficult version of the task in which the stimulus duration was reduced from 1.0 to 0.5 seconds. The performance was then assessed on an easier version of the task in which the stimulus duration was increased from 1.0 to five seconds. Because omissions were increased to the same degree in all three versions of the task, and because accuracy was unaffected by ll o glycine infusions in all three versions of the task, it could be determined that the increase in omissions likely did not reflect an attention deficit.
The possibility that the change in omissions reflected a decrease in motivation was also excluded as the reward retrieval latency was not systematically affected by l alle glycine infusions. Although it takes several weeks for rats to attain criterion performance on the final stage of the five choice serial reaction time task. Once the animals have learned the task, their performance is generally quite stable.
As a result, it is possible to test individual subjects repeatedly. This can decrease the number of animals needed for any one experiment.
