The overall goal of this procedure is to study the acquisition of a complex four limb reaching task and the analysis of its two phases within session learning and between session learning. This is accomplished by first familiarizing the animal with the experimenter and the learning environment. The second step is to teach the rat to realign its body prior to each food pellet retrieval with the tongue.
Next, the rat learns how to grasp with its four limbs for the sugar pellet placed on a pedestal. Once its preferred, forelimb is determined, the pedestal is shifted to optimize the angle of access for pellet grasping during the training period, each trial is scored as a success, a drop, or a failure. The main advantage of this technique or existing methods, like the classical single palate reaching task, is to increase the difficulty of motor learning, allowing the investigation of more complex foreign movements.
Visual demonstration of this method is critical as the different steps are difficult to explain in a manuscript text, seeing, hearing, and reading the individual steps, allowing more complete way to explain the technique. To prepare the animals for the experiment, handle them daily for at least five days, proceeding the experiments such sessions should take 10 to 15 minutes per animal. Utilize this opportunity to weigh them.
When initially handling a rat, just let the animals get used to your hand being in their cage. Then gently lift the animal in a safe manner. Weigh each animal to establish their baseline body weight prior to food deprivation.
Three days before the pre-training begins during the habituation period, start the starvation protocol. Give the rats just 0.05 grams of standard diet per gram of body weight. Daily access to water should not be restricted.
Make sure that each rat does not lose more than 10%of its body weight during the period of food restriction. If several animals are held in one cage, it will probably be necessary to feed them separately so the dominant animal does not eat all the food. To acquaint the rat with the grasping apparatus, put it into the training box for five days prior to the start of pre-training with daily sessions lasting 10 to 15 minutes.
Also place several pellets into the training box to familiarize the animal with their smell and taste. Lastly, between exposure to each animal, be sure to clean the training box. Male and female rats must be trained in separate rooms.
The training room must be calm and quiet. Preferably do not mix male and female rats in the same study. After the rats have been familiarized with the training box, start the pre-training.
Return each rat to the box and place a sugar pellet on the slide in front of the slid opening so the animal can reach it with its tongue. Now teach the rat to either run to the rear of the cage and return to the slit opening for the next pellet, or to step back and turn around its own access. To get another pellet.
Allow the rat to explore the cage during execution of this task. If the rat fails to do this properly, gently tap the rear of the cage with forceps to catch its attention. Once the rat goes to the rear of the cage, gently tap the front of the cage to attract its attention.
Back to the slit opening. This step will take patience Pal. Retrieval with the tongue is crucial at this stage, and usually the animal's method of choice.
An attempt of pal retrieval with the for during the pre-training period is D For an exclusion criteria Define having learned the task as when the rat can execute it a certain number of times within a timeframe, such as 50 tongue pellet, retrievals within 15 minutes, train each rat daily for up to an hour until the criteria are met. Non learner rats can usually be identified within a few days of pre-training. They should be excluded from the study during the pre-training.
It is important to continue starving the rats. They should retain free access to water, and their weight should be monitored daily. For the task learning, replace the slide in front of the training box with a pedestal.
Then place the pellet on the pedestal, which is 1.5 centimeters away from the window so that it cannot be reached by the tongue, but only with a forelimb. To teach the animal how to grasp the pellet, move the pellet close to the rat's mouth using forceps, and then retract it. When the rat sticks out its tongue and attempts to lick it, continue teasing the rat in this way until it stretches out.
Its forelimb to grasp the pellet. During the first 10 reaching attempts, the pedestal is positioned in the middle of the slit opening to determine the paw preference. If seven or more of the first 10 trials are accomplished with the same forelimb that paw is considered as the preferred paw, if this threshold is not reached, continue looking through subsequent 10 trial blocks until a preference is shown.
A preference must also be maintained between 10 trial blocks and generally is after determining preference. Shift the pedestal to the window border contrary to the preferred limb, thus giving the animal a better angle of access to the palate. With its preferred limb score each pellet presentation as a success, a drop or a failure.
A drop includes a successful grasp followed by its loss. A success occurs when the rat successfully grasps the pellet and retrieves it to its mouth to finally eat the pellet. Perform one session per day.
Use a trial number limit and a time limit to define the session duration. For example, end the session after either 150 pellet grasps or an hour, whichever comes first. Precision and fine tuning can be determined in the analysis of a rat's success on its first attempt to retrieve a pellet.
Success on the first attempt occurs only when the rat makes a single monolithic movement. Without disruption, hesitation, or repetition of an individual movement component, always take note of these types of success. During the motor skill learning, it is important to continue starving the rats.
As in pre-training, never hold back access to water and weigh each rat daily. While many rats learn the task, some fail, they may be unmotivated or lose interest. After several failures, they may be too rushed and aggressive to learn the task.
There are also rats that show early success, but then lose their ability to improve or even drop in success. Success can be defined in two phases. An initial fast learning component representing primary acquisition is usually observed in the first training session.
The second phase consists of skilled motor learning, which takes more time and represents consolidation of the learned task over several sessions. Rats take a varying number of days to accomplish this level of learning, resulting in averaged curves that are not too smooth. Another expression of successful motor learning can be seen in the fine tuning of the motor plan.
In each training session, the fraction of pellets retrieved on a first attempt compared to all successes can measure this sort of motor learning. While attempting this procedure, it's important to stay calm, provide a comfortable and noise free environment during the sessions, and to food restrict the animals while monitoring their weights. This procedure can be combined with other methods, such as treatment with specific drugs, different imaging techniques, electrophysiology or genetic modifications.
This multitude of experimental combinations offers a good basis for a better understanding of motor learning.
