title: Synergistic tonic and phasic activity of the locus coeruleus norepinephrine (LC-NE) arousal system is required for optimal attentional performance.
abstract: A certain level of arousal is required for an individual to perform optimally, and the locus coeruleus norepinephrine (LC-NE) system plays a central role in optimizing arousal. Tonic firing of LC-NE neurons needs to be held within a narrow range of 1-3 Hz to facilitate phasic firing of the LC-NE neurons; these two modes of activity act synergistically, to allow the individual to perform attentional tasks optimally. How this information can be applied to further our understanding of psychiatric disorders has not been fully elucidated. Here we propose two models of altered LC-NE activity that result in attentional deficits characteristic of psychiatric disorders: 1) 'hypoaroused' individuals with e.g. attention-deficit/hyperactivity disorder (ADHD) have decreased tonic firing of the LC-NE system, resulting in decreased cortical arousal and poor attentional performance and 2) 'hyperaroused' individuals with e.g. anxiety disorders have increased tonic firing of the LC-NE system, resulting in increased cortical arousal and impaired attentional performance. We argue that hypoarousal (decreased tonic firing of LC-NE neurons) and hyperarousal (increased tonic firing of LC-NE neurons) are suboptimal states in which phasic activity of LC-NE neurons is impeded. To further understand the neurobiology of attentional dysfunction in psychiatric disorders a translational approach that integrates findings on the LC-NE arousal system from animal models and human imaging studies may be useful.
authors.affiliation: Department of Psychiatry, Faculty of Health Sciences, University of Cape Town, Observatory, 7925 Cape Town, South Africa. howellsfleur@gmail.com
authors.forename: Fleur M
authors.initials: FM
authors.lastname: Howells
authors.forename: Dan J
authors.initials: DJ
authors.lastname: Stein
authors.forename: Vivienne A
authors.initials: VA
authors.lastname: Russell
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D001008:Anxiety Disorders / Q000503:physiopathology; D001143:Arousal / Q000502:physiology*; D001288:Attention / Q000502:physiology*; D001289:Attention Deficit Disorder with Hyperactivity / Q000503:physiopathology; D004195:Disease Models, Animal; D006801:Humans; D008125:Locus Coeruleus / Q000473:pathology / Q000502:physiology*; D008959:Models, Neurological