Effects of L-dopa during auditory instrumental learning in humans

• Published in: PloS one 2012-12, Vol.7 (12), p.e52504-e52504
• Main Authors: Weis, Tina, Puschmann, Sebastian, Brechmann, Andre, Thiel, Christiane M
• Format: Article
• Language: English
• Subjects: Adult; Analysis of Variance; Auditory discrimination learning; Auditory Perception - drug effects; Auditory plasticity; Auditory stimuli; Behavior - drug effects; Behavioral plasticity; Biology; Brain Mapping; Conditioning, Operant - drug effects; Cortex (auditory); Dihydroxyphenylalanine; Dopamine; Dopamine receptors; Dopaminergic Neurons - drug effects; Dopaminergic Neurons - physiology; Female; Functional magnetic resonance imaging; Functional plasticity; Humans; L-dopa; Learning; Learning Curve; Levodopa; Levodopa - administration & dosage; Levodopa - pharmacology; Linear Models; Magnetic resonance; Magnetic Resonance Imaging; Male; Mesencephalon - drug effects; Mesencephalon - physiology; Modulation; Neuroimaging; Neurosciences; Operant conditioning; Oxygen - blood; Pharmacology; Phenols (Class of compounds); Reaction time; Reaction time task; Reinforcement; Rodents; Social and Behavioral Sciences; Studies
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0052504

The dopaminergic neurotransmitter system is critically involved in promoting plasticity in auditory cortex. We combined functional magnetic resonance imaging (fMRI) and a pharmacological manipulation to investigate dopaminergic modulation of neural activity in auditory cortex during instrumental learning. Volunteers either received 100 mg L-dopa (Madopar) or placebo in an appetitive, differential instrumental conditioning paradigm, which involved learning that a specific category of frequency modulated tones predicts a monetary reward when fast responses were made in a subsequent reaction time task. The other category of frequency modulated tones was not related to a reward. Our behavioral data provides evidence that dopaminergic stimulation differentially impacts on the speed of instrumental responding in rewarded and unrewarded trials. L-dopa increased neural BOLD activity in left auditory cortex to tones in rewarded and unrewarded trials. This increase was related to plasma L-dopa levels and learning rate. Our data thus provides evidence for dopaminergic modulation of neural activity in auditory cortex, which occurs for both auditory stimuli related to a later reward and those not related to a reward.