title: Individual capacity differences predict working memory performance and prefrontal activity following dopamine receptor stimulation.
abstract: Dopamine receptors are abundant in the prefrontal cortex (PFC), a critical region involved in working memory. This pharmacological fMRI study tested the relationships between dopamine, PFC function, and individual differences in working memory capacity. Subjects performed a verbal delayed-recognition task after taking either the dopamine receptor agonist bromocriptine or a placebo. Behavioral effects of bromocriptine treatment depended on subjects' working memory spans, with the greatest behavioral benefit for lower span subjects. After bromocriptine, PFC activity was positively correlated with a measure of cognitive efficiency (RT slope) during the probe period of the task. Less efficient subjects with slower memory retrieval rates had greater PFC activity, whereas more efficient subjects had less activity. After placebo, these measures were uncorrelated. These results support the role of dopamine in verbal working memory and suggest that dopamine may modulate the efficiency of retrieval of items from the contents of working memory. Individual differences in PFC dopamine receptor concentration may thus underlie the behavioral effects of dopamine stimulation on working memory function.
authors.affiliation: University of California, Berkeley, California, USA. sebgibbs@psych.stanford.edu
authors.forename: Sasha E B
authors.initials: SE
authors.lastname: Gibbs
authors.forename: Mark
authors.initials: M
authors.lastname: D'Esposito
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001143:Arousal / Q000187:drug effects; D001971:Bromocriptine / Q000494:pharmacology*; D003463:Cues; D018491:Dopamine Agonists / Q000494:pharmacology*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D007206:Individuality; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008570:Memory, Short-Term / Q000187:drug effects* / Q000502:physiology; D009043:Motor Activity / Q000187:drug effects; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D011237:Predictive Value of Tests; D017397:Prefrontal Cortex / Q000098:blood supply / Q000187:drug effects* / Q000502:physiology; D011930:Reaction Time / Q000187:drug effects; D013223:Statistics as Topic; D013997:Time Factors
chemical_list: D018491:Dopamine Agonists; D001971:Bromocriptine