title: Serotonin and dopamine differentially affect appetitive and aversive general Pavlovian-to-instrumental transfer.
abstract: BACKGROUND
  Human motivation and decision-making is influenced by the interaction of Pavlovian and instrumental systems. The neurotransmitters dopamine and serotonin have been suggested to play a major role in motivation and decision-making, but how they affect this interaction in humans is largely unknown.
  
  
  OBJECTIVE
  We investigated the effect of these neurotransmitters in a general Pavlovian-to-instrumental transfer (PIT) task which measured the nonspecific effect of appetitive and aversive Pavlovian cues on instrumental responses.
  
  
  METHODS
  For that purpose, we used selective dietary depletion of the amino acid precursors of serotonin and dopamine: tryptophan (n = 34) and tyrosine/phenylalanine (n = 35), respectively, and compared the performance of these groups to a control group (n = 34) receiving a nondepleted (balanced) amino acid drink.
  
  
  RESULTS
  We found that PIT differed between groups: Relative to the control group that exhibited only appetitive PIT, we found reduced appetitive PIT in the tyrosine/phenylalanine-depleted group and enhanced aversive PIT in the tryptophan-depleted group.
  
  
  CONCLUSIONS
  These results demonstrate a differential involvement of serotonin and dopamine in motivated behavior. They suggest that reductions in serotonin enhance the motivational influence of aversive stimuli on instrumental behavior and do not affect the influence of appetitive stimuli, while reductions in dopamine diminish the influence of appetitive stimuli. No conclusions could be drawn about how dopamine affects the influence of aversive stimuli. The interplay of both neurotransmitter systems allows for flexible and adaptive responses depending on the behavioral context.
authors.affiliation: Department of Systems Neuroscience, University Medical Center Hamburg-Eppendorf, W34, Martinistraße 52, 20251, Hamburg, Germany, m.hebart@uke.de.
authors.forename: Martin N
authors.initials: MN
authors.lastname: Hebart
authors.forename: Jan
authors.initials: J
authors.lastname: Gläscher
mesh_terms: D000328:Adult; D001066:Appetite / Q000502:physiology*; D003214:Conditioning, Classical / Q000502:physiology*; D003463:Cues; D003657:Decision Making / Q000502:physiology*; D004032:Diet; D004298:Dopamine / Q000172:deficiency / Q000378:metabolism*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D009042:Motivation / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000172:deficiency / Q000378:metabolism; D010649:Phenylalanine / Q000172:deficiency / Q000378:metabolism; D012701:Serotonin / Q000172:deficiency / Q000378:metabolism*; D014364:Tryptophan / Q000172:deficiency / Q000378:metabolism; D014443:Tyrosine / Q000172:deficiency / Q000378:metabolism; D055815:Young Adult
chemical_list: D018377:Neurotransmitter Agents; D012701:Serotonin; D014443:Tyrosine; D010649:Phenylalanine; D014364:Tryptophan; D004298:Dopamine