title: Effects of the noradrenergic agonist clonidine on temporal and spatial attention.
abstract: BACKGROUND
  Recent theories posit an important role for the noradrenergic system in attentional selection in the temporal domain. In contrast, the spatially diffuse topographical projections of the noradrenergic system are inconsistent with a direct role in spatial selection.
  
  
  OBJECTIVE
  To test the hypotheses that pharmacological attenuation of central noradrenergic activity should (1) impair performance on the attentional blink task, a task requiring the selection of targets in a rapid serial visual stream of stimuli; and (2) leave intact the efficiency of the search for a target in a two-dimensional visuospatial stimulus array.
  
  
  METHODS
  Thirty-two healthy adult human subjects performed an attentional blink task and a visual search task in a double-blind, placebo-controlled, between-subject study investigating the effects of the alpha2 adrenoceptor agonist clonidine (150 microg, oral dose).
  
  
  RESULTS
  No differential effects of clonidine vs placebo were found on the attentional blink performance. Clonidine slowed overall reaction times in the visual search task but did not impair the efficiency of the visual search.
  
  
  CONCLUSIONS
  The attentional blink results are inconsistent with recent theories about the role of the noradrenergic system in temporal filtering and in mediating the attentional blink. This discrepancy between theory and data is discussed in detail. The visual search results, in combination with previous findings, suggest that the noradrenergic system is not directly involved in spatial attention processes but instead can modulate these processes in an indirect fashion.
authors: Department of Psychology, Leiden University, Wassenaarseweg 52, 2333 AK, Leiden, The Netherlands. snieuwenhuis@fsw.leidenuniv.nl
authors: Sander
authors: S
authors: Nieuwenhuis
authors: I Caroline
authors: IC
authors: van Nieuwpoort
authors: Dick J
authors: DJ
authors: Veltman
authors: Madeleine L
authors: ML
authors: Drent
mesh_terms: D000293:Adolescent; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000328:Adult; D001288:Attention / Q000187:drug effects*; D017660:Autoreceptors / Q000819:agonists; D001767:Blinking / Q000187:drug effects*; D003000:Clonidine / Q000494:pharmacology*; D003463:Cues; D004311:Double-Blind Method; D005260:Female; D005403:Fixation, Ocular / Q000187:drug effects; D006801:Humans; D008125:Locus Coeruleus / Q000378:metabolism; D008297:Male; D011930:Reaction Time / Q000187:drug effects*; D013028:Space Perception / Q000187:drug effects*
chemical_list: D000316:Adrenergic alpha-Agonists; D017660:Autoreceptors; D003000:Clonidine