An important question in sensory neuroscience is what coding strategies and mechanisms are used by the brain to detect and discriminate among behaviorally relevant stimuli. To address the noisy response properties of individual neurons, sensory systems often utilize broadly tuned neurons with overlapping receptive fields at the system's periphery, resulting in homogeneous responses among neighboring populations of neurons. It has been hypothesized that progressive response heterogeneity in ascending sensory pathways is evidence of an efficient encoding strategy that minimizes the redundancy of the peripheral neural code and maximizes information throughput for higher level processing. This hypothesis has been partly supported by the documentation of neural heterogeneity in various cortical structures.This dissertation examines whether selective and sensitive responses to behaviorally relevant stimuli contribute to a heterogeneous and efficient encoding in the auditory midbrain. Prior to this study, no compelling experimental framework ex- My parents, for their support throughout all of my education. Not only did they instill in me a confidence that I could take on any educational challenge, but they supported me when I chose not to take these challenges on. I'm sure they worried about me when I dropped out of college in 1993, but their trust in my own decision making process was a better lesson for me to learn at the time.My sister, for teaching me how to fight for the important things in life.My entire committee, for challenging me to push my limits (which I discovered on many occasions). I have leaned on each and every one of them at different times through this process. I am very grateful to have had access to a group so diverse in their specialties, yet so consistent in their kindness, approachability, depth of knowledge, and eagerness to share this knowledge. I couldn't have done this without a single one of them.Lonneke Eeuwes, for all of the long hours she spent collecting data for our experiii iments and carefully reading through my manuscripts.Sunghan Kim, for working with me through the technical details of our state space frequency tracking methods. My research was made possible by your work.Roberto Santiago, for taking me under his wing as a fresh graduate student and imbuing me with a sense of adventure about research. He taught me that the challenges inherent in science are not a chore, but a privilege to be relished.John Vasallo, for setting time aside for our weekly musical catharsis and for being flexible with respect to my constantly shifting schedule. He almost single handedly ensured that playing music will continue to be an important part of my life.Todd Haynes, for his roving intellect and dedication to the creative process. I can only hope that I can tap into a similar wellspring of enthusiasm, kindness, and vision.