Georg Dirnberger

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Random number generation (RNG) engages a number of executive processes. We used positron emission tomography (PET) to measure regional cerebral blood flow (rCBF) in six volunteers who performed RNG and a control counting (COUNT) task at six rates paced by a tone. This provided a systematic variation of difficulty of RNG. Relative to COUNT, RNG was(More)
Random number generation is an attention-demanding task that engages working memory and executive processes. Random number generation requires holding information 'on line', suppression of habitual counting, internally driven response generation and monitoring of responses. Evidence from PET studies suggests that the dorsolateral prefrontal cortex (DLPFC)(More)
Parkinson's disease involves impaired activation of frontal cortical areas, including the supplementary motor area and prefrontal cortex, resulting from impaired thalamocortical output of the basal ganglia. Electrophysiologically, such impaired cortical activation may be seen as a reduced amplitude of the contingent negative variation (CNV), a slow negative(More)
Executive dysfunction can be present from the early stages of Parkinson's disease (PD). It is characterized by deficits in internal control of attention, set shifting, planning, inhibitory control, dual task performance, and on a range of decision-making and social cognition tasks. Treatment with dopaminergic medication has variable effects on executive(More)
Evidence from PET studies suggests that the dorsolateral prefrontal cortex (DLPFC) is involved in generation of random responses. We used TMS to examine the specific role of this area in random generation of responses, a task which requires holding information 'on line', suppression of habitual or stereotyped response patterns, intrinsic response(More)
A pervasive hypothesis in the timing literature is that temporal processing in the milliseconds and seconds range engages the basal ganglia and is modulated by dopamine. This hypothesis was investigated by testing 12 patients with Parkinson's disease (PD), both 'on' and 'off' dopaminergic medication, and 20 healthy controls on three timing tasks. In a(More)
The basal ganglia and cerebellum are considered to play a role in timing, although their differential roles in timing remain unclear. It has been proposed that the timing of short milliseconds-range intervals involves the cerebellum, whereas longer seconds-range intervals engage the basal ganglia (Ivry, 1996). We tested this hypothesis using positron(More)
Executive dysfunction in Parkinson's disease is well documented, but it is still unclear whether this results from (i) prefrontal dysfunction, (ii) striatal dysfunction, or (iii) altered striatal outflow to the prefrontal cortex. To clarify this issue, we used H(2)(15)O PET to asses six nondemented and nondepressed patients with Parkinson's disease and six(More)
Time perception is compromised in emotional situations, yet our ability to remember these events is enhanced. Here we suggest how the two phenomena might be functionally linked and describe the neural networks that underlie this association. We found that participants perceived an emotionally aversive stimulus longer than it was, compared to an immediately(More)
Contingent negative variation (CNV) was recorded from electrodes F7, F3, Fz, F4, F8, T7, C3, Cz, C4, T8, P7, P3, Pz, P4 and P8 in 19 young (mean age: 23 years) and 15 elderly (mean age: 66 years) healthy right-handed subjects, using a S2-choice paradigm. Young subjects showed early peak negativity shortly after the warning stimulus over mid-frontal areas,(More)