Evaluating Skilled Prehension in Mice Using an Auto-Trainer

Our technology automates a complicated behavioral analysis that can save time and serve as a springboard for many different types of studies. With our technique, the task and the reward are the same thing. There's no disconnect between performing a vague task, possibly incorrectly, and receiving a reward.

Animal models provide an opportunity for testing approaches to augment recovery after a neurological injury. For example, in my lab we test approaches to augment recovery post-stroke, since there is an urgent need to develop innovative new approaches to post-stroke rehabilitation. In addition to stroke, our auto-trainer could be useful for studying motor learning before injury, as well as in models of Parkinson's, Alzheimer's, or traumatic brain injury.

When a mouse reaches it's goal weight, start a training session by placing a 45 milligram pellet on the pellet surface directly in front of the slot, and allow the mouse to retrieve the pellet. When the mouse associates an open slot with being fed, use a pair of tweezers to hold a pellet in the same position that the mouse has retrieved the pellets previously. As the mouse begins to bite for the pellet, pull the pellet away approximately half a centimeter, such that the pellet is out of reach of the mouth.

When the mouse extends a paw through the slot, reinforce the behavior by allowing the mouse to eat the pellet. While not instrumental to experimentation, record whether the left or right paw is preferred. As the mouse associates extending a paw with eating a pellet, further reinforce the behavior by withholding the pellet in response to attempts to retrieve the pellet with the mouth and tongue.

Take care to stop your mice from successfully getting a pellet without using a paw, or they will learn bad habits that are hard to unlearn. Finalize the introduction of the desired paw-reaching behavior by placing the 45-milligram pellet just under one centimeter from the outer edge of the cage gate, such that the left or right-most point of the pellet is tangent to a line extending straight out from the edge of the cage gate slot. Then allow the mouse to attempt to retrieve the pellet, being vigilant to remove the pellet and prevent it's consumption if the mouse should attempt retrieval by some other method than paw extension.

Before beginning the training session, click the Run arrow in the LabVIEW Interface of the auto-trainer and note the bait pellet sensor reading, both with and without a pellet in place. Click Stop to stop the test run and change the bait pellet sensor target to a value between those two readings. Place the modified mouse cage on the auto-trainer and affix the cage gate.

Then align the pellet to the edge of the slot as in the manual procedure, and open a new training session in the LabVIEW Interface. Input the information as required to record data about the training session and click the Mouse ID field to enter the file name of each training session. Click the Total Pellets to Dispense During Routine field to control how many pellets are dispensed for a single experiment.

Click the Pause After Pellet Number field to set a five second pause after the indicated pellet is removed from the diving board, and click the Pause Length field to set a pause in between the time a pellet is removed from the diving board and the time a new pellet is dispensed. Set the auto-trainer to manually record the distance at which the pellet is placed in the Reach Distance field, and click the Folder to Contain Logs field to select the file location to save the collected data. Once the information fields have been filled out, click Run to begin the training session.

The auto-trainer will dispense individual pellets and track whether they fall through the funnel, until the total number of pellets has been dispensed and the last pellet has either been retrieved or dropped by the mouse. The program will stop automatically at this point. If necessary, it can also be stopped prematurely by clicking on the Stop button.

Once the software is set up, place the home cage of the mouse to be tested on the pedestal and click Run to allow the mouse to investigate the slot and it's new unfamiliar surroundings. Mice trained with the auto-trainer learned the prehension task and exhibit a clear increase in motor skill. This increase in skill is similar to that observed where the animal is trained manually without the use of the auto-trainer.

Make sure to make the mice use their paws. If you let them think you're just letting them have food, they won't reach for you. An injury can be induced to any part of the motor pathway to determine what effects the lesion has on motor performance, and how to encourage recovery from said lesion.