BEHAVIORAL AND BRAIN SCIENCES (2016), Page 1 of 75 doi:10.1017/S0140525X15000667, e200 Norepinephrine ignites local hotspots of neuronal excitation: How arousal amplifies selectivity in perception and memory Mara Mather Davis School of Gerontology, University of Southern California, Los Angeles, CA 90089-0191
[email protected] David Clewett Neuroscience Graduate Program, University of Southern California, Los Angeles, CA 90089-2520
[email protected] Michiko Sakaki School of Psychology and Clinical Language Sciences, University of Reading, Reading RGX 7BE, United Kingdom; and Kochi University of Technology, Kami, 782-0003, Japan
[email protected] Carolyn W. Harley Professor Emeritus, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
[email protected] Abstract: Emotional arousal enhances perception and memory of high-priority information but impairs processing of other information. Here, we propose that, under arousal, local glutamate levels signal the current strength of a representation and interact with norepinephrine (NE) to enhance high priority representations and out-compete or suppress lower priority representations. In our "glutamate amplifies noradrenergic effects" (GANE) model, high glutamate at the site of prioritized representations increases local NE release from the locus coeruleus (LC) to generate “NE hotspots.” At these NE hotspots, local glutamate and NE release are mutually enhancing and amplify activation of prioritized representations. In contrast, arousal-induced LC activity inhibits less active representations via two mechanisms: 1) Where there are hotspots, lateral inhibition is amplified; 2) Where no hotspots emerge, NE levels are only high enough to activate low-threshold inhibitory adrenoreceptors. Thus, LC activation promotes a few hotspots of excitation in the context of widespread suppression, enhancing high priority representations while suppressing the rest.