The effect of D-amphetamine, clonidine, and yohimbine on human information processing

Psychophysiology. 1994 Jul;31(4):331-7. doi: 10.1111/j.1469-8986.1994.tb02441.x.


Twelve subjects were tested with D-amphetamine, yohimbine, clonidine, and a placebo on a task with two levels of stimulus and two levels of response complexity. The purpose of this study was to test the hypothesis that noradrenergic drugs affect early stimulus processes. D-amphetamine speeded reaction time (RT), clonidine slowed it, and yohimbine had no effect. D-amphetamine and yohimbine decreased N1 latency and clonidine increased it. D-amphetamine and yohimbine decreased P3 latency and clonidine increased it but, in each case, only when latency estimates were based on single trials, not on averages. D-amphetamine's effect on RT, not P3, as measured by the average, is consistent with previous results. Single trial measures appear more sensitive. Speeding of N1 and single-trial P3 data indicate that noradrenergic drugs affect processing of early (visual) information. D-amphetamine's speeding of single-trial P3 estimates was attributed to its noradrenergic actions. Yohimbine's speeding of P3 without changing RT is consistent with neural net (parallel) simulations but not with a serial model. These findings support the assumption that different neurotransmitters modulate specific cognitive processes.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Attention / drug effects
  • Clonidine / pharmacology*
  • Cognition / drug effects*
  • Dextroamphetamine / pharmacology*
  • Electroencephalography / drug effects
  • Evoked Potentials, Visual / drug effects*
  • Humans
  • Male
  • Psychomotor Performance / drug effects*
  • Reaction Time / drug effects*
  • Yohimbine / pharmacology*


  • Yohimbine
  • Clonidine
  • Dextroamphetamine