Dr Carol Barnes has been interested in the brain circuits responsible for memory and how these circuits change during aging for over 4 decades. She has applied behavioral and electrophysiological methods to the study of plasticity and circuit properties of the medial temporal lobe over that time, including in vivo evoked field potential recordings in chronically-implanted freely-behaving rats, and intracellular and extracellular recordings in vitro. She was instrumental (with McNaughton) in the development of ensemble tetrode recording methods for single units in awake young and old rats. More recently she has extended these methods to young and aged nonhuman primates, with chronic implants of hyperdrive recording devices that are capable of individually lowering multiple tetrodes into the hippocampus while monkeys behave. Another approach she uses to understand behavior-driven circuits is the single cell gene expression imaging method “catFISH”, which was developed in her laboratory (Guzowski et al., 1999). The immediate early gene Arc is induced in a cell-specific fashion in the brain by neural activity associated with attentive, active behavior. With this method the activity history of individual cells in a population can be determined for two different time points within the same animal (ex vivo). This method contributed to moving the field closer to the goal of behavior-driven whole brain imaging with single cell resolution. Barnes directs the Evelyn F. McKnight Brain Institute at the University of Arizona and the Division of Neural Systems, Memory and Aging. She is actively involved in collaborative projects with scientists within the state of Arizona, across the United States and the world. She has a track record of conducting difficult, systematic and thorough studies with interdisciplinary teams, as well as with her own students and postdoctoral fellows – projects that have been followed through to publication, a number of which are now classic references on brain aging and behavior.