The Structure of Skilled Forelimb Reaching in the Rat: A Movement Rating Scale

Before reach Training can begin a ratchet. First become accustomed to the food that it will be reaching for in the training apparatus. To do this, a small amount of the food is introduced into the animal's home cage for two to three consecutive days before reach.

Training begins when introduced to a novel location like the reaching box. The test subject will take a greater length of time to begin eating an unknown food source than a familiar one. A rat will usually spend the first session in the reaching box, investigating the surroundings and habituating to the box.

Several pellets are placed on the reaching tray well within the reach of the animal's tongue. The goal for session one is to familiarize the rat with the food and the food's location, so reaching with the tongue is acceptable. If the test animal is sufficiently interested in the food, it may be moved further away from the reaching slot to encourage the use of the paw while habituating the rat to reaching.

It is acceptable to keep many pellets on the tray to increase reaching success and to reinforce the preference for paw usage. Once A Clear preference for reaching with a paw is established, indentations in the reaching tray are used to give the rat only two food pellets to reach for. This will help determine which paw is dominant.

When paw dominance is established, the rat is limited to the use of that paw by only placing one food pellet on the shelf, either left or right. The goal of session two Is to develop consistent, skillful reaching behavior. As such, pellets are in the reaching indentations in rapid succession.

No scoring of the session occurs. The focus of stage three is to develop a pattern of reaching in the rat that will allow the researcher to analyze each reach as a distinct and separate observable event. Because researchers are interested in analyzing not only skillful palm manipulation, but also entire body posture, it is important the rat performs each reach as a distinct and separate event.

The researcher uses the rat's natural behavior patterns to shape a behavior that is desirable to the testing methods. After performing a reach, whether successful or not, the researcher will wait until the rat has returned to the rear of the cage before placing the next food pellet. The test animal will soon associate returning to the rear of the cage with a food reward and will return to the rear of the cage after each reach attempt.

While this calls for some patients in the initial stages of the training process, the average test subject will quickly conform to the behavior Shaping. If the test animal Bobbles or drops the food pellet, the researcher may quickly remove the pellet from the food tray. This procedure should foster increased concentration on single reach success, and reduce redundant Reaching.

Once a rat has Attained a sufficient reaching proficiency, non rewarding reach behavior may be minimized through additional training. During a complete reach sequence, a rat will usually probe the reaching slot with its nose. The goal of this session is to train the animal to identify the presence or absence of a food pellet.

If the rat approaches sniffs and reaches when there is no food pellet, the behavior is unrewarding. The researcher must wait until the test subject has returned from a trip to the rear of the cage. Identifies that there is no food pellet and does not reach A Properly trained animal, will not reach when a pellet is not present.

This step may also take some patients on the part of the researcher, but can be accomplished even in very short sessions. Once the Test animals consistently perform each trial as a distinct and separate event returning to the rear of the cage, after each reach, the researchers should begin an informal scoring process that will allow them to determine when baseline competency has been achieved. Baseline competency is defined as a plateau in the test, animals reaching scores.

During the informal scoring sessions, the 10 minute duration is abandoned in preference of a 10 20 pellet regime. Each subject is given 10 pellets as a warmup followed by, followed by 20 scored pellets. It is recommended that the pellets be laid out in advance.

To avoid confusion, test animals will typically reach baseline competency after eight to 10 sessions of training. Formal scoring for data acquisition may begin after 10 to 14 sessions. A reach Is defined as any advance of the paw through the reaching slot.

A trial begins with The test animal at the back of the cage and consists of an approach of the reaching slot, followed by a reach action that ends in either a hit or a miss. A miss is defined as any movement of the paw through the slot that does not Retrieve a pellet. A hit Occurs when the animal makes a reaching movement successfully grasps the food pellet and transports the food to its mouth.

The pellet must be eaten for a reach to be Successful. In principle, a number of scoring procedures can be used. The most liberal of the scoring measurements in Method one reaches are not recorded.

The only information required is whether or not the animal obtained a pellet during a Single trial. Method Two is the most common of the measurement schemes in this method. The total number of hits in animal scores is divided by the total number of reaches it Performs.

Method Three Is the most demanding of the measurement schemes. In this measurement, a hit is scored if and only if the food target is acquired in a single reach during a trial.