Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2010.Cataloged from PDF version of thesis.Includes bibliographical references.The basal ganglia, and specifically the sensorimotor (dorsolateral) striatum, have been implicated in stimulus-response learning. Here, I analyze the role the striatum plays in learning. We recorded from neurons of the sensorimotor striatum as rats learn, are over-trained, are extinguished, and are re-trained on a discriminative T-maze task. In this T-maze a gate was lowered immediately after an auditory click and the rats were allowed to proceed down the long arm of the maze. Mid-run, one of two tones was played. Rats had to choose to turn down either the left or right arm of the T-maze based on which tone was played. We discovered that population neural activity becomes restructured during learning and overtraining to emphasize the beginning and end of each trial. We also created a short-term memory version of the T-maze task by moving the location of the tone cue in order to determine if this affects the strength of the restructuring seen in the firing patterns of the striatum as learning progressed. Lastly, we examined the relationship the training induced pattern had to learning the tone-turn association and to other things that changed systematically throughout learning, such as speed./ by Terra D. Barnes.Ph.D.