, Volume 132, Issue 4, pp 315–323

Alteration of brain noradrenergic activity in rhesus monkeys affects the alerting component of covert orienting

  • E. A. Witte
  • R. T. Marrocco

DOI: 10.1007/s002130050351

Cite this article as:
Witte, E. & Marrocco, R. Psychopharmacology (1997) 132: 315. doi:10.1007/s002130050351


 Experiments were conducted to elucidate the role of the noradrenergic neurotransmitter system in arousal and the orienting of attention. Rhesus monkeys were trained to perform a peripherally cued, covert orienting task for juice reward, and their manual reaction times (RTs) to visual stimuli were measured. The effects of parenteral injections of the α-2 adrenergic agonists clonidine and guanfacine, and normal saline were compared on the covert task. We assessed 1) overall error rates, 2) the difference in RTs between validly and invalidly cued trials (validity effect), 3) the difference in RTs between neutral and no-cue trials (alerting effect), 4) target location (visual field), and 5) cue-target interval. Changes in noradrenaline levels produced by clonidine (and to a lesser extent guanfacine) significantly decreased the alerting effect, and lowered RTs to stimuli in the left visual field, but did not change the validity effect, suggesting that noradrenaline is involved in maintaining non-spatial, sensory readiness to external cues but not in the shifting of the attentional focus.

Key words Attention Alerting Clonidine Guanfacine Monkey Reaction times 

Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • E. A. Witte
    • 1
  • R. T. Marrocco
    • 1
  1. 1.Institute of Neuroscience, 1254 University of Oregon, Eugene, OR 97403-1254, USAUS

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