J Psychiatry Neurosci 2013; 39(2):110-7
Christina Andreou, MD, PhD*; Kristina Veith*; Vasilis P. Bozikas, MD, PhD; Tania M. Lincoln, PhD; Steffen Moritz, PhD
Andreou, Veith, Moritz — University Medical Center Hamburg-Eppendorf, Department of Psychiatry and Psychotherapy, Hamburg, Germany; Bozikas — 1st Department of Psychiatry, Aristotle University of Thessaloniki, Thessaloniki, Greece; Lincoln — Department of Psychology, University of Hamburg, Hamburg, Germany
Background: Enhanced automatic spreading of activation in the semantic network has been suggested to underlie formal thought disorder in patients with schizophrenia, but it is not clear how this relates to the dopaminergic dysfunction implicated in the disorder. Previous studies on dopaminergic modulation of priming in healthy volunteers have focused on controlled rather than automatic processes. The present study aimed to examine the effects of both a dopaminergic agonist and a dopaminergic antagonist on semantic priming while minimizing the contribution of controlled processes.
Methods: We investigated the effects of levodopa (L-Dopa; 100 mg), haloperidol (2 mg) and placebo on priming in healthy participants within a randomized, double-blind, crossover design. We used a pronunciation priming task with word triplets; the middle word was an ambiguous word, whereas the first word of the triplet served to provide either a congruent, incongruent or unbiased context for the target word. Two stimulus onset asynchronies (SOA) were used: 150 ms and 750 ms.
Results: The study involved 34 participants. At an SOA of 150 ms, L-Dopa accelerated responses to incongruent targets and subordinate targets of ambiguous words, whereas haloperidol was associated with faster responses in congruent contexts and dominant targets. At an SOA of 750 ms, haloperidol accelerated responses to subordinate targets.
Limitations: Modulations in the relative magnitude of priming according to substance and condition rather than absolute priming were assessed.
Conclusion: Effects of L-Dopa on automatic priming processes appear to be different than those on controlled processes. Our results are consistent with those of studies on semantic priming and the effects on antipsychotics in patients with schizophrenia.
Submitted Feb. 25, 2013; Revised May 21, 2013; Accepted July 2, 2013.
Acknowledgments: We thank Anna Schildt and Aljoscha Rieger for their help with participant recruitment and testing. This work was partly supported by a grant to C. Andreou by the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG, Project-Nr: AN970/1-1).
Competing interests: None declared.
Contributors: C. Andreou, V. Bozikas and S. Moritz designed the study. K. Veith and T.M. Lincoln acquired the data, which C. Andreou analyzed. C. Andreou, K. Veith and S. Moritz wrote the article, which all authors reviewed and approved for publication.
Correspondence to: C. Andreou, University Medical Center Hamburg-Eppendorf, Department of Psychiatry and Psychotherapy, Martinistrasse 52, 20246 Hamburg, Germany; email@example.com