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Dopamine agonist stimulation reduces activity in brain networks linked to impulse control and response inhibition, according to a new study. In PD non- gamblers, activity in these areas increased in response to the same stimulation. PET imaging was performed before and after apomorphine administration in 14 PD patients, 7 with DA-induced pathological gambling, and 7 without. During each imaging session, the patient engaged in a simple card choice test, which rewarded a correct choice with a visual display indicating the correct choice had been made. The effect of DA administration was opposite in the two groups. In non- gamblers, administration of apomorphine "significantly increased activity" in the left lateral orbitofrontal cortex (OFC), right rostral cingulate zone (RCZ), right amygdala, and left ventral anterior external pallidum (GPe), "while gamblers showed a significant DA-induced reduction of neuronal activity in these regions." In gamblers, the decrease in activity correlated with an increase in gambling symptoms following DA administration, as determined by a symptom questionnaire. "Hypoactivity of the lateral OFC has previously been reported in drug addiction and pathological gambling in non-PD subjects," the authors note, "and is thought to play a crucial role in assigning subjective value to actions by encoding and updating expectations of future rewards or punishments....The RCZ is thought to be engaged in monitoring functions that are involved in preventing negative consequences." They conclude, "We propose that in vulnerable patients with PD, DAs produce an abnormal neuronal pattern that resembles those found in nonparkinsonian pathological gambling and drug addiction." Drug-induced deactivation of inhibitory networks predicts pathological gambling in PD T van Eimeren, G Pellechia, R Cilia, B Ballanger, TDL Steeves, S Houle, JM Miyasaki, M Zurowski, AE Lang, AP Strafella Neurology 2010;75:1711-1716 ---------------------------------------------------------------------- To sign-off Parkinsn send a message to: mailto:[log in to unmask] In the body of the message put: signoff parkinsn