Project Abstract In this proposal we will deploy state-of-the-art neural ensemble recordings across the reach and saccadic- attention cortices of NHP performing coordinated reach-and-saccade movements to test hypotheses about the multiregional brain mechanisms supporting coordinated visual behavior. There is growing evidence that an important way to conceptualize the behavioral significance of multiregional brain dynamics is as communication channels that mediate information transmission between sender brain regions and receiver brain regions. The communication channel allows populations of neurons in a sender region to dynamically influence the activity of populations of neurons in a receiver region and support behavioral flexibility. We channel the will coordinated seek to test the communication model of multiregional communication by asking how the model explains neural i nteractions between neurons in the saccade and reach regions that must communicate during coordinated visual behavior. We specifically investigate multiregional communication during behaviors in which visual fixation enhances reach and saccade movement performance.One way to demonstrate the importance of fixation to accurate reaching is to present a second target around the time of a coordinated look and reach or pointing movement, and instruct subjects to acquire the newly-presented target with a new saccadic eye movement. This sequence of two movements, the coordinated look-and-reach movement and the subsequent saccadic eye movement, reveals that the importance of target foveation to accurate reaching extends beyond the act of fixation. Accurate coordinated looking and reaching features a form of attentional suppression that inhibits saccades to newly-presented targets. As a result, gaze is said to be temporarily anchored to the target of the coordinated reach and, importantly, the longer the duration of fixation is extended, the more accurate the reach movement. Gaze anchoring therefore provides an opportunity to investigate the multiregional mechanisms of a flexible behavior in terms of communication between at least two separate systems in the brain - the reach system that controls the reach and the saccade system that is inhibited to suppress new saccades. We will first do experiments to test and elaborate the conceptual framework of communication channels for multiregional communication during gaze anchoring. Aims 1 and 2 will test complementary hypotheses involving subspaces and neural coherence for how communication between reach and saccadic-attentional cortex gives rise to coordinated behavioral performance. In Aim 3, we will then more closely examine the cognitive processes in play and select between alternative explanations for how coordinated visual behavior depends on attention. These experiments will advance understanding of how channel gain and modulation combine in the mechanisms of multiregional communication, will lead to new strategies for neural rehabi...