Abstract: The objective of the proposed research is to understand the diverse lamina-specific neurons, and connections between the dorsolateral prefrontal cortex (DLPFC) and the rostral aspect of the dorsal premotor cortex (PMdr) during decision-making. Decision-making refers to our ability to choose and perform appropriate actions based on sensory cues and context to achieve behavioral goals. Pressing the brakes to stop the car in response to a red light or choosing what dress to wear are common decisions that we make in our everyday life. Disrupted activity in brain areas such as the DLPFC and PMdr contribute to the impairments in decision-making observed in mental illness. Our past work and other research has provided some insight into the involvement of DLPFC and PMdr in decision-making and that these areas are strongly interconnected. However, we currently do not understand 1) the relationship between biophysical properties and morphological structure, and in vivo decision-related activity of neurons in different layers of these brain areas, and 2) whether the connections between DLPFC and PMdr are feedforward, feedback or lateral (both feedforward and feedback). We address these open questions by using a multimodal approach that combines in vivo neurophysiology in DLPFC and PMdr of behaving monkeys, decoding and granger causality analysis, optical stimulation of DLPFC inputs to PMdr, tract tracing experiments and in vitro single neuron electrophysiology and morphometry in slices from the same subjects. Our first aim uses laminar multi-contact electrodes to investigate neuronal responses across layers of PMdr, and DLPFC while monkeys perform a novel decision-making task that separates perceptual decisions from action selection. We will investigate if in vivo differences are related to differences in biophysical and morphological properties of these neurons with in vitro whole-cell patch-clamp recordings of lamina-specific neurons in PMdr slices. In Aim 2, we examine the granger causality between the local field potentials recorded simultaneously in DLPFC and PMdr to understand whether DLPFC sends a feedforward driving input or a modulating feedback input. We combine these in vivo experiments with anatomical tracing experiments in DLPFC to understand the bidirectional laminar pattern of DLPFC and PMdr connections. In Aim 3, we will inject an opsin in DLPFC and stimulate the anterograde fibers in PMdr in vivo to causally investigate whether the pattern of activity induced in PMdr by stimulation of DLPFC is consistent with feedforward, feedback, or lateral connections. To obtain a more detailed understanding of the pattern of inputs from DLPFC to PMdr, we will investigate in vitro synaptic responses of these PMdr neurons in layers 3 and 5 to optical stimulation of afferent DLPFC fibers and localize the morphological compartments of PMdr neurons to which DLPFC afferent fibers provide inputs. Impact: This project will elucidate the in vivo and in...