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In Parkinson's disease (PD), it is possible that tonic increase of dopamine associated with levodopa medication overshadows phasic release of dopamine, which is essential for learning. Thus while the motor symptoms of PD are improved with levodopa medication, learning would be disrupted. To test this hypothesis, we investigated the effect of levodopa(More)
Recent imaging studies in healthy controls with a conditional stop signal reaction time (RT) task have implicated the subthalamic nucleus (STN) in response inhibition and the pre-supplementary motor area (pre-SMA) in conflict resolution. Parkinson's disease (PD) is characterized by striatal dopamine deficiency and overactivity of the STN and underactivation(More)
Sequence knowledge acquired by repeated exposure to targets in a speeded localization task was studied in 3 experiments that sought to test A. Destrebecqz and A. Cleeremans's (2001, 2003) claim that, under certain circumstances, the expression of such sequence knowledge cannot be brought under intentional control. In Experiment 1 participants were trained(More)
Evidence from animal, clinical, and imaging studies suggests that the basal ganglia and their frontal connections mediate motor inhibition, but the role of dopamine remains unclear. The aim of our study was to investigate, for the first time, whether levodopa medication influences motor inhibition and conflict resolution on the conditional stop-signal(More)
The distinction between implicit (unconscious) and explicit (conscious) learning is controversial. Some argue that explicit learning is dependent on the medial temporal lobes, whereas implicit learning is mediated by the basal ganglia and others propose that all learning is explicit. The purpose of the present study was to investigate the involvement of the(More)
Previous studies indicate that a variety of pharmacological agents interfere with the prepulse inhibition of the acoustic startle (PPI) response including phencyclidine (PCP), 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), amphetamine, and apomorphine. Strain differences have been observed in the ability of apomorphine to disrupt PPI, although the(More)
Exposure to a repeating sequence of target stimuli in a speeded localization task can support both priming of sequence-consistent responses and recognition of sequence components. In 3 experiments with both deterministic and probabilistic sequences, the authors used a novel procedure in which measures or priming and recognition were taken concurrently and(More)
It has been proposed that procedural learning is mediated by the striatum and, it has been reported that patients with Parkinson's disease (PD) are impaired on the weather prediction task (WPT) which involves probabilistic classification learning with corrective feedback (FB). However, PD patients were not impaired on probabilistic classification learning(More)
Normal actions and behaviors often require inhibition of unwanted and inadequate movements. Motor inhibition has been studied using the stop signal task, in which participants are instructed to respond to a go signal. Sporadically, a stop signal is also delivered after a short interval following the go signal, prompting participants to inhibit their already(More)
We examined learning and expression of contextual implicit learning of a sequence of targets in a speeded target-detection task in amnesic and control participants. Amnesia was of organic origin in one participant group and induced psychopharmacologically (diazepam 7.5 or 15 mg) in another. Although the amnesic groups were able to learn the target sequence(More)