Differential dopaminergic modulation of executive control in healthy subjects

Abstract

Our findings suggest that dopamine agonists modulate two EC tasks differently. Furthermore, there seems to be a selective modulation of different aspects of the Stroop task.

Acute Serotonin and Dopamine Depletion Improves Attentional Control: Findings from the Stroop Task

“…The improved Stroop performance following dopamine depletion (like serotonin depletion) suggests greater attentional control, as these effects were observed independent of effects on general speed of information processing (ie, overall reaction time). These findings are somewhat contrary to the findings of Roesch-Ely et al (2005) who found decreased Stroop interference with stimulation of D 2 receptors. These findings are also contrary to molecular imaging studies (ie, PET Imaging with [ 18 F]FDOPA) in which a negative association between regional [ 18 F]FDOPA uptake (a measure of dopamine synthesis) and Stroop interference has been found in normal control subjects and patients with Parkinson's disease and schizophrenia (Bruck et al, 2005(Bruck et al, , 2001McGowan et al, 2004).…”

“…Obviously this would have hindered our ability to detect any changes in Stroop facilitation under the different treatment conditions, although previous studies have also not found any changes in facilitation following dopaminergic or serotonergic modulation (Roesch-Ely et al, 2005;Schmitt et al, 2000). Despite this, future research may consider using faster stimulus presentation, or a larger sample size, in order to reproduce this phenomenon of facilitation (Barch et al, 2004), and to extend our observations.…”

“…In addition, findings from the 5-CSRTT indicate that premature responding (or failure of behavioral inhibition) can be decreased in rats by the dopamine D 2 receptor agonist quinpirole, which is thought to decrease dopaminergic neurotransmission by stimulating presynaptic dopamine D 2 receptors (Passetti et al, 2003); while increasing dopamine neurotransmission with amphetamine and cocaine (Cole and Robbins, 1987;Harrison et al, 1997;van Gaalen et al, 2006) and with dopamine reuptake inhibitors (van Gaalen et al, 2006) increases premature responding, an effect that is suppressed with dopamine D 2 receptor antagonism (van Gaalen et al, 2006) and dopamine depletion (Cole and Robbins, 1987). Together, these findings suggest that the findings by Roesch-Ely et al (2005) of decreased Stroop interference (ie, improved attentional control) with stimulation of D 2 receptors may reflect a presynaptic mechanism leading to decreased dopamine neurotransmission. This is also supported by the evidence that haloperidol (a D 2 antagonist which inhibits post-synaptic dopamine transmission) has been shown to similarly reduce Stroop interference in healthy participants (Williams et al, 1996).…”

“…For instance, tyrosine/phenylalanine depletion is thought to affect global brain dopamine function via modulation of the synthesis and transport processes (Fadda, 2000;Oldendorf and Szabo, 1976;Reilly et al, 1997), while the method used by Roesch-Ely et al (2005), that is the administration of a dopamine D 2 receptor agonist, is thought to affect dopaminergic function through stimulation of D 2 receptors specifically, at either cortical or striatal areas. Further, given that D 2 receptors are found both pre-and post-synaptically on dopamine neurons in different agonist affinity states (Wolf and Roth, 1987), the resultant effect on dopamine neurotransmission may vary depending on the site of action and the dosage.…”

“…Similarly, studies examining the role of dopamine on Stroop performance (using dopamine agonists) have also yielded inconsistent results. For example, stimulation of dopamine D 2 receptors using bromocriptine decreased Stroop interference (Roesch-Ely et al, 2005), while increasing synaptic dopamine with the indirect dopamine agonist, amphetamine, had no effect (Barch and Carter, 2005). Both studies, however, found no effects of dopaminergic modulation on Stroop facilitation, while the latter study also found improved reaction times to all stimuli (Barch and Carter, 2005).…”