DESCRIPTION Abstract: I propose a new technology that will fundamentally change our understanding of brain function and the relationship with behavior. Examining complex functions, such as vision, hearing, memory, attention, decision making, or sleep, have been traditionally performed by studying the brain of nonhuman primates in a laboratory environment in which the head and body are restrained while synthetic stimuli are presented on a computer monitor. However, it has become increasingly understood that studying the brain in a restrained laboratory rig poses severe limits on our capacity to understand the function of brain circuits. Indeed, when responses of individual neurons are measured in naturalistic settings they tend to be different compared to when they are measured in the laboratory environment. In addition, it has always been unclear whether phenomena well described in laboratory conditions, such as adaptation, learning, or decision making, can be replicated when animals freely move in their natural environment. To overcome these limitations, I will construct a wireless system that will allow neuroscientists to study cortical dynamics and plasticity at the population level while nonhuman primates are moving freely in their natural environment. Studying brain function in an unconstrained environment will open new opportunities. Phenomena that were difficult or impossible to observe in an experimental rig, such as foraging, sleep, or social behavior will now become possible to study. Our technology will allow us to acquire vastly more brain data than has ever been gathered in live subjects, at a much higher rate than is possible today. The large quantity of contiguous neural data recorded by such a system will be of great interest to clinicians and theorists studying general properties of normal and dysfunctional neural networks. Our system will lead not only to medical insights into the mechanisms of brain disorders, but also to practical applications for neuronal pros