Cody Brooks

Pavlovian Conditioning, Memory, Emotion, and Relapse

My research program involves basic research on the learning and memory processes that modulate emotionally- and motivationally- significant experiences, and the behaviors that accompany those experiences.  I am especially interested in the use of animal models to better understand the learning and memory processes that underlie instances of human relapse of problematic behaviors with emotional components (e.g., substance abuse, anxiety, depression).  Believe it or not, the methods of Pavlovian conditioning are uniquely suited to the study of these and any emotion-based behaviors.

Since Ivan P. Pavlov's time in Russia (circa 1890-1925), psychologists and other scientists have come to realize the fundamental importance of Pavlovian (classical) conditioning for the development of and change in many involuntary ("non-conscious" and other) responses experienced by humans and other animals.  These responses are the result of Pavlovian conditioning, and include heart rate, blood pressure, respiratory, and perspiration changes; emotional reactions like anxiety, fear, excitement, frustration; drug tolerance, withdrawal and craving; and motivational influences on many voluntary behaviors such as feeding, competition, reproduction, and pleasure-seeking activities, to name just a few.

An increasingly popular idea about Pavlovian conditioning is that it results in the formation of memories involving the events that are present in an organism's environment when they have emotionally-significant experiences.  My research focuses on what the content of those memories is, and what happens to those memories (e.g., how memorable they become) usually at some time after they have formed.  Sometimes various different memories can interact, and in some cases, the memory of a particular experience can be retrieved more or less well compared to other memories. This disparity in the ability to retrieve certain memories can produce dramatic changes in behavior.

My research is directed at three interrelated fronts:

1. The study of animal models of relapse in humans.  One of the more interesting implications of our research here is that clinical relapses (of substance abuse, anxiety-disorders, depression, and so on) occur in part because crucial information learned during the treatment of a disorder is forgotten rather readily after the formal course of treatment ends (i.e., relapse is likely when a period of time has passed, or the setting changes, following treatment).  Using a model involving rats as subjects, my research has shown that laboratory instances of relapse can be reduced or eliminated by straightforward memory retrieval techniques.  (The implications of this research for human treatment are rather important.  Psychology has developed fairly good technologies for the treatment of common psychological disorders like anxiety and depression, but unfortunately, relapse rates post-treatment are disturbingly high.  More information is needed about why relapses occur, and how they can be minimized or completely prevented.) My students and I have found that the memory processes that underlie relapse and its reduction are similar in both aversive and appetitive motivational systems, i.e., when animals form initial memories about either "positive" or "negative" experiences.  One objective of our research is to continue to study the basic memory mechanisms that contribute to various types of relapse, and those that may contribute to reducing relapses.
2. Our research has implications for a basic understanding of conditioning and memory involving important emotional events.  Some contemporary theories of conditioning and memory can explain the instances of relapse and their reduction that we have been studying intensively (e.g., hierarchical associative learning theories about occasion setting and contextual control).  Other theories cannot.  The theories that suggest explanations are relatively straightforward neural network models that can simulate many conditioning effects.  My students and I conduct ongoing tests of these theories using experimental designs that we hope will advance our understanding of not only the clinically-relevant relapse phenomena, but of the general memory processes involved in motivation & emotions.
3. Recently, I have begun a project to study alcohol tolerance, withdrawal, and relapse, with the intention of influencing the probability or magnitude of craving-related responses and relapses that motivate an individual to resume alcohol use/abuse.  I believe this work has direct relevance to human substance abuse patterns.  There is always interest in determining whether learning and memory processes shown with nonhuman animals also apply to human experience, behavior, and memory.  I am beginning to investigate drug-use related relapse-like effects in human memory, with particular interest in discovering whether relapses might be reduced by reminder treatments analogous to those I've established with other methods.

I would be happy to talk with students about any aspect of these intriguing and challenging areas of research, and related topics.  Please contact me for questions or comments about my research program.