Dopamine and semantic activation: an investigation of masked direct and indirect priming.
To investigate the effects of dopamine on the dynamics of semantic activation, 39 healthy volunteers were randomly assigned to ingest either a placebo (n = 24) or a levodopa (n = 16) capsule. Participants then performed a lexical decision task that implemented a masked priming paradigm. Direct and indirect semantic priming was measured across stimulus onset asynchronies (SOAs) of 250, 500 and 1200 ms. The results revealed significant direct and indirect semantic priming effects for the placebo group at SOAs of 250 ms and 500 ms, but no significant direct or indirect priming effects at the 1200 ms SOA. In contrast, the levodopa group showed significant direct and indirect semantic priming effects at the 250 ms SOA, while no significant direct or indirect priming effects were evident at the SOAs of 500 ms or 1200 ms. These results suggest that dopamine has a role in modulating both automatic and attentional aspects of semantic activation according to a specific time course. The implications of these results for current theories of dopaminergic modulation of semantic activation are discussed.
Angwin
Anthony J
AJ
Centre for Research in Language Processing and Linguistics, The University of Queensland, Brisbane, Australia. a.angwin@uq.edu.au
Chenery
Helen J
HJ
Copland
David A
DA
Arnott
Wendy L
WL
Murdoch
Bruce E
BE
Silburn
Peter A
PA
D000328:Adult; D018491:Dopamine Agonists / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007980:Levodopa / Q000008:administration & dosage / Q000494:pharmacology; D010470:Perceptual Masking; D012660:Semantics; D013060:Speech / Q000187:drug effects*; D014705:Verbal Behavior / Q000187:drug effects
D018491:Dopamine Agonists; D007980:Levodopa