Thomas Polak

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According to the Reinforcement Sensitivity Theory (RST), Gray's dimension of impulsivity, reflecting human trait reward sensitivity, determines the extent to which stimuli activate the Behavioural Approach System (BAS). The potential neural underpinnings of the BAS, however, remain poorly understood. In the present study, we examined the association between(More)
OBJECTIVE Visuospatial deficits are among the first symptoms of Alzheimer disease (AD) and linked to lower activation in the superior parietal cortex as assessed with functional imaging. Near-infrared spectroscopy (NIRS) is an optical method to measure changes in the concentration of oxygenated hemoglobin and deoxygenated hemoglobin in the microvascular(More)
The method of vagus somatosensory evoked potentials (VSEP) was introduced to easily measure the activity of vagus brain stem nuclei. In Alzheimer's disease, this measure was characterized by longer latencies as compared to controls while amplitudes did not show statistical significant differences at frontal and central recording sites. Therefore, the(More)
The extinction of conditioned fear depends on an efficient interplay between the amygdala and the medial prefrontal cortex (mPFC). In rats, high-frequency electrical mPFC stimulation has been shown to improve extinction by means of a reduction of amygdala activity. However, so far it is unclear whether stimulation of homologues regions in humans might have(More)
An approach bias for alcohol stimuli (i.e. faster approach than avoidance reactions) might facilitate relapses in alcohol dependence. Neurobiological models suggest hypersensitivity in the reward system [inter alia nucleus accumbens and orbitofrontal cortex (OFC)] to cause pathologically enhanced approach impulses towards alcohol stimuli. At the same time,(More)
BACKGROUND The reinforcement sensitivity theory postulates a behavioral inhibition system that modulates reaction to stimuli indicating aversive events. Gray's dimension of anxiety, reflecting human trait sensitivity to aversive events, determines the extent to which stimuli activate the behavioral inhibition system. Although structural brain imaging has(More)
OBJECTIVE Vagus somatosensory evoked potentials (VSEP) are far-field potentials probably generated in nuclei of then. vagus in the lower brainstem. They represent a putative, easily applicable method for discrimination between patients with Alzheimer's disease (AD), patients with mild cognitive impairment (MCI), and healthy controls (HC). METHODS Thirteen(More)
OBJECTIVE Several neuroscience tools showed the involvement of auditory cortex in chronic tinnitus. In this proof-of-principle study we probed the capability of functional near-infrared spectroscopy (fNIRS) for the measurement of brain oxygenation in auditory cortex in dependence from chronic tinnitus and from intervention with transcranial magnetic(More)
In Alzheimer's disease (AD), the degeneration of brainstem nuclei is different from major depression (MD). Thus, vagus somatosensory evoked potentials (VSEP) proposed for the functional assessment of brainstem nuclei should show prolonged latencies in AD but not in MD. In 55 AD patients, 57 MD patients and two age-matched control groups evoked potentials(More)
Vagus somatosensory-evoked potentials (VSEP) were proposed as a neurophysiological indicator of brainstem dysfunction based on prolonged latencies found in Alzheimer's dementia and Parkinson's disease. We now aimed at a further confirmation of this view independent from neurodegenerative diseases and hypothesized that VSEP in multiple sclerosis with(More)