Norepinephrine (NE) medications affect attention and the ability to ignore distracting stimuli. Current theories focus on prefrontal cortex (PFC) as the site of NE-induced modulation. Sensory cortex neurons are also affected by NE. We propose testing the hypothesis that NE may actually affect attention via direct action in sensory cortex. To test this hypothesis, we will develop a rat spatial attention task that is analogous to those used in the nonhuman primate. Head-fixed rats will be presented with a train of whisker deflection stimuli on both sides of the face and will have to report detection of the reward-predicting stimulus in a train of distractors via operant response. On alternating trial blocks, cues will direct spatial attention to a whisker on one or the other side of the face. We will then perform concurrent extracellular recordings from barrel cortex neurons, which respond selectively to whisker deflections on one side of the face, but not the other. We will test the hypothesis that stimulus encoding will be modulated when attention is directed in the receptive field of the neurons. Such modulations have been shown to originate in the PFC, which targets layer 6 of sensory cortices. We will record all cortical layers simultaneously to test the hypotheses that modulation occurs in layer 6 first and is then transmitted to other layers. Finally, we will test the novel theory that NE may modulate attention by acting directly in sensory cortex. To this aim, we will conduct simultaneous barrel cortex and locus coeruleus recordings and examine the relationship of their stimulus-evoked responses (micro- and mesoscopic signals) during attention. We have been developing a novel animal model of attention that is amicable to genetics and physiology methods which are more feasible in rodents. These experiments will expand our understanding of the mechanisms of attention to individual cortical layers and assess the role NE may play in this mechanism.