title: Levodopa enhances explicit new-word learning in healthy adults: a preliminary study.
abstract: OBJECTIVE
  While the role of dopamine in modulating executive function, working memory and associative learning has been established; its role in word learning and language processing more generally is not clear. This preliminary study investigated the impact of increased synaptic dopamine levels on new-word learning ability in healthy young adults using an explicit learning paradigm.
  
  
  METHODS
  A double-blind, placebo-controlled, between-groups design was used. Participants completed five learning sessions over 1 week with levodopa or placebo administered at each session (five doses, 100 mg). Each session involved a study phase followed by a test phase. Test phases involved recall and recognition tests of the new (non-word) names previously paired with unfamiliar objects (half with semantic descriptions) during the study phase.
  
  
  RESULTS
  The levodopa group showed superior recall accuracy for new words over five learning sessions compared with the placebo group and better recognition accuracy at a 1-month follow-up for words learnt with a semantic description.
  
  
  CONCLUSIONS
  These findings suggest that dopamine boosts initial lexical acquisition and enhances longer-term consolidation of words learnt with semantic information, consistent with dopaminergic enhancement of semantic salience.
authors.affiliation: UQ Centre for Clinical Research, The University of Queensland, Brisbane, Australia.|School of Health and Rehabilitation Sciences, Division of Speech Pathology, The University of Queensland, Brisbane, Australia.
authors.forename: Leanne
authors.initials: L
authors.lastname: Shellshear
authors.affiliation: UQ Centre for Clinical Research, The University of Queensland, Brisbane, Australia.
authors.forename: Anna D
authors.initials: AD
authors.lastname: MacDonald
authors.affiliation: UQ Centre for Clinical Research, The University of Queensland, Brisbane, Australia.
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Mahoney
authors.affiliation: School of Health and Rehabilitation Sciences, Division of Speech Pathology, The University of Queensland, Brisbane, Australia.
authors.forename: Emma
authors.initials: E
authors.lastname: Finch
authors.affiliation: UQ Centre for Advanced Imaging, The University of Queensland, Brisbane, Australia.
authors.forename: Katie
authors.initials: K
authors.lastname: McMahon
authors.affiliation: UQ Centre for Clinical Research, The University of Queensland, Brisbane, Australia.
authors.forename: Peter
authors.initials: P
authors.lastname: Silburn
authors.affiliation: Brain Mapping Unit, Department of Psychiatry, University of Cambridge, Cambridge, UK.|School of Psychology and Psychiatry, Monash University, Melbourne, Australia.
authors.forename: Pradeep J
authors.initials: PJ
authors.lastname: Nathan
authors.affiliation: UQ Centre for Clinical Research, The University of Queensland, Brisbane, Australia.|School of Health and Rehabilitation Sciences, Division of Speech Pathology, The University of Queensland, Brisbane, Australia.
authors.forename: David A
authors.initials: DA
authors.lastname: Copland
mesh_terms: D000328:Adult; D015259:Dopamine Agents / Q000008:administration & dosage / Q000494:pharmacology*; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D064368:Healthy Volunteers; D006801:Humans; D007802:Language; D007858:Learning / Q000187:drug effects*; D007980:Levodopa / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D057567:Memory, Long-Term / Q000187:drug effects; D011939:Mental Recall / Q000187:drug effects; D010865:Pilot Projects; D021641:Recognition, Psychology / Q000187:drug effects; D055815:Young Adult
chemical_list: D015259:Dopamine Agents; D007980:Levodopa
keywords: dopamine; language learning; lexical acquisition; non-word