Methods of Improving Learning and Memory Performance in the Radial Arm Maze

Abstract

Assessing learning and memory through the use of a radial arm maze (RAM) is a common approach within the areas of psychology and neuroscience. This apparatus requires that the animal model remember which arms of the maze have been visited and which have yet to be explored in an effort to retrieve all food rewards present. Traditionally, errors are noted as entries into already visited arms, and the intrinsic penalty for such a choice is a sense of wasted time and energy. This method of testing is inefficient, however, as the intrinsic penalty is not salient enough to motivate the animal to avoid errors. As such, learning curves, wherein a high number of errors eventually decreases to very few errors, take a long time to establish using these traditional methods. It was hypothesized that implementing an aversive stimulus (a mild shock) as penalty for error would lead to a shift in learning curves, wherein mice that receive the penalty would show faster acquisition of the task relative to those who do not receive the penalty. The use of shock in the RAM is not a novel idea in and of itself, but previous research has employed this technique by either making the entire length of the arm gridded for shock or attaching a small shock clip to either the ear or foot of the animal. Both of these approaches create confounds wherein the shock is largely inescapable, leading to an increase in stress. The apparatus used in the current study employed shock via shock plates embedded into a small portion of each arm; as such, the mice would experience a penalty but also be able to withdraw and escape. Results indicate that mice who received the penalty performed significantly better on the task than mice who did not experience shock.