Reliance on habits at the expense of goal-directed control following dopamine precursor depletion. de Wit, S., Standing, H. R., Devito, E. E., Robinson, O. J., Ridderinkhof, K. R., Robbins, T. W., & Sahakian, B. J. Psychopharmacology, 219(2):621–631, January, 2012. Place: Germany
doi  abstract   bibtex   
RATIONALE: Dopamine is well known to play an important role in learning and motivation. Recent animal studies have implicated dopamine in the reinforcement of stimulus-response habits, as well as in flexible, goal-directed action. However, the role of dopamine in human action control is still not well understood. OBJECTIVES: We present the first investigation of the effect of reducing dopamine function in healthy volunteers on the balance between habitual and goal-directed action control. METHODS: The dietary intervention of acute dietary phenylalanine and tyrosine depletion (APTD) was adopted to study the effects of reduced global dopamine function on action control. Participants were randomly assigned to either the APTD or placebo group (ns = 14) to allow for a between-subjects comparison of performance on a novel three-stage experimental paradigm. In the initial learning phase, participants learned to respond to different stimuli in order to gain rewarding outcomes. Subsequently, an outcome-devaluation test and a slips-of-action test were conducted to assess whether participants were able to flexibly adjust their behaviour to changes in the desirability of the outcomes. RESULTS: APTD did not prevent stimulus-response learning, nor did we find evidence for impaired response-outcome learning in the subsequent outcome-devaluation test. However, when goal-directed and habitual systems competed for control in the slips-of-action test, APTD tipped the balance towards habitual control. These findings were restricted to female volunteers. CONCLUSIONS: We provide direct evidence that the balance between goal-directed and habitual control in humans is dopamine dependent. The results are discussed in light of gender differences in dopamine function and psychopathologies.
@article{de_wit_reliance_2012,
	title = {Reliance on habits at the expense of goal-directed control following dopamine precursor depletion.},
	volume = {219},
	copyright = {All rights reserved},
	issn = {1432-2072 0033-3158},
	doi = {10.1007/s00213-011-2563-2},
	abstract = {RATIONALE: Dopamine is well known to play an important role in learning and motivation. Recent animal studies have implicated dopamine in the reinforcement  of stimulus-response habits, as well as in flexible, goal-directed action.  However, the role of dopamine in human action control is still not well  understood. OBJECTIVES: We present the first investigation of the effect of  reducing dopamine function in healthy volunteers on the balance between habitual  and goal-directed action control. METHODS: The dietary intervention of acute  dietary phenylalanine and tyrosine depletion (APTD) was adopted to study the  effects of reduced global dopamine function on action control. Participants were  randomly assigned to either the APTD or placebo group (ns = 14) to allow for a  between-subjects comparison of performance on a novel three-stage experimental  paradigm. In the initial learning phase, participants learned to respond to  different stimuli in order to gain rewarding outcomes. Subsequently, an  outcome-devaluation test and a slips-of-action test were conducted to assess  whether participants were able to flexibly adjust their behaviour to changes in  the desirability of the outcomes. RESULTS: APTD did not prevent stimulus-response  learning, nor did we find evidence for impaired response-outcome learning in the  subsequent outcome-devaluation test. However, when goal-directed and habitual  systems competed for control in the slips-of-action test, APTD tipped the balance  towards habitual control. These findings were restricted to female volunteers.  CONCLUSIONS: We provide direct evidence that the balance between goal-directed  and habitual control in humans is dopamine dependent. The results are discussed  in light of gender differences in dopamine function and psychopathologies.},
	language = {eng},
	number = {2},
	journal = {Psychopharmacology},
	author = {de Wit, Sanne and Standing, Holly R. and Devito, Elise E. and Robinson, Oliver J. and Ridderinkhof, K. Richard and Robbins, Trevor W. and Sahakian, Barbara J.},
	month = jan,
	year = {2012},
	pmid = {22134475},
	pmcid = {PMC3249188},
	note = {Place: Germany},
	keywords = {*Habits, Adaptation, Adaptation, Psychological/drug effects/*physiology, Adult, Amino Acids/blood/pharmacology, Conditioning, Conditioning, Operant/drug effects/*physiology, Dopamine/deficiency/*physiology, Female, Humans, Male, Middle Aged, Operant/drug effects/*physiology, Phenylalanine/blood/*deficiency, Psychological/drug effects/*physiology, Tyrosine/blood/*deficiency},
	pages = {621--631},
}

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