doi: 10.3389/fnhum.2015.00144 Personal involvement is related to increased search motivation and ... more doi: 10.3389/fnhum.2015.00144 Personal involvement is related to increased search motivation and associated with activity in left BA44—a pilot study
Arbeitsgedaechtnis - Grundlagen und Therapie [Working memory - Basics and therapy]
Hypothalamic response to GLP-1 agonist exenatide is associated with reduced food intake
Software systems for the analysis of multi-modal brain data
Age differences in exerting top-down control over neutral and emotional information in working memory
Attentional top-down modulation of mnemonic representations: When you’re old, you like it emotional, when you’re young, you like it neutral
Variants of FTO modulate reward-related behavior and the central control of hunger and satiety
Arbeitsgedächtnis - Aktuelles aus Forschung und Klinik [Working memory - Current topics from research and clinic]
Attentional selection of mnemonic representations reduces the BOLD response in the intraparietal sulcus
Exercise impacts brain structure: A longitudinal VBM and TBSS study in overweight and obese subjects
Re-directing attention to objects in working memory can enhance their representational fidelity. ... more Re-directing attention to objects in working memory can enhance their representational fidelity. However, how this attentional enhancement of memory representations is implemented across distinct, sensory and cognitive-control brain network is unspecified. The present fMRI experiment leverages psychophysical modelling and multivariate auditory- pattern decoding as behavioral and neural proxies of mnemonic fidelity. Listeners performed an auditory syllable pitch-discrimination task and received retro-active cues to selectively attend to a to-be-probed syllable in memory. Accompanied by increased neural activation in fronto-parietal and cingulo-opercular networks, valid retro-cues yielded faster and more perceptually sensitive responses in recalling acoustic detail of memorized syllables. Information about the cued auditory object was decodable from hemodynamic response patterns in superior temporal sulcus (STS), fronto-parietal, and sensorimotor regions. However, among these regions ...
Mirror visual feedback (MVF) is a promising approach to enhance motor performance without trainin... more Mirror visual feedback (MVF) is a promising approach to enhance motor performance without training in healthy adults as well as in patients with focal brain lesions. There is preliminary evidence that a functional modulation within and between primary motor cortices as assessed with transcranial magnetic stimulation (TMS) might be one candidate mechanism mediating the observed behavioral effects. Recently, studies using task-based functional magnetic resonance imaging (fMRI) have indicated that MVF-induced functional changes might not be restricted to the primary motor cortex (M1) but also include higher order regions responsible for perceptual-motor coordination and visual attention. However, aside from these instantaneous task-induced brain changes, little is known about learning-related neuroplasticity induced by MVF. Thus, in the present study, we assessed MVF-induced functional network plasticity with resting-state fMRI (rs-fMRI). We performed rs-fMRI of 35 right-handed, health...
Gender Moderates Structural Changes in the Brain's Reward System of Obese Humans
What is the optimum fMRI procedure with auditory stimulation?
Introduction: Functional MRI in auditory experiments is a challenge because the scanning procedur... more Introduction: Functional MRI in auditory experiments is a challenge because the scanning procedure produces considerable noise that can interfere with the auditory paradigm. The loud and unpleasant noise might mask the auditory presentation or interfere with stimuli designed to evoke positive emotions. Therefore, scanning protocols appear to be advantageous that allow interleaved auditory stimulation and image acquisition. The sparse temporal sampling (STS) technique utilizes a long repetition time (TR) in order to achieve a stimulus presentation in the absence of scanner noise. Although there are only a few volumes in the resulting data sets, studies have demonstrated remarkable results (1,2). A more recent development is the interleaved-silent steady-state (ISSS) technique, which provides a stimulus presentation during silence with a higher temporal efficiency (3).
Correlations between gray and white matter structure in obese and lean women
Leptin-dependent correlations between gray and white matter structure in obese and lean women
Eigenvector centrality mapping based on low-frequency phase alignment
Introduction. Our brain acts like a small world network much like the World Wide Web (WWW). There... more Introduction. Our brain acts like a small world network much like the World Wide Web (WWW). Therefore, techniques known from internet search engines such as Google's PageRank that specifically exploit small world properties of the WWW can be assumed to work well for analyzing brain data. We have recently proposed a variant of Google's PageRank called ``eigenvector centrality mapping'' (ECM) as a new analysis method for fMRI data (Lohmann et al, 2010). In ECM, each voxel receives a rank describing its centrality (hubness) within the brain. Centrality measures depend on a metric describing similarity between time series. In our previous study, we had used ECM based on spectral coherence which assesses linear dependence between time series as a function of temporal frequencies. However, this measure ignores phase shifts between time series so that time series may receive high coherence values even though they are separated by large phase shifts. In the present work, we specifically focus on such phase shifts and investigate whether changes in brain state may produce phase adjustments such that fMRI time series become more closely aligned in time. We re-evaluated rs-fMRI data of 22 subjects who were scanned in two sessions comparing a hungry versus a sated state and computed ECM based on a phase alignment measure. We found regionally specific and statistically significant changes in phase centrality between the two scans.
Bullet-Points with max. 85 characters including spaces) • We developed an MRI-method estimating a... more Bullet-Points with max. 85 characters including spaces) • We developed an MRI-method estimating arterial/venous CBV and BOLD signal changes. • Hemodynamics of excitation and inhibition was investigated in human brain at 7T. • We found different timecourses, layer-dependence and arterio-venous interaction. • Our results suggest different neurovascular coupling for excitation and inhibition.
Recent studies have revealed that the internal representations that we construct from the environ... more Recent studies have revealed that the internal representations that we construct from the environment and maintain in visual short-term memory (VSTM) to guide behavior are highly flexible and can be selectively modulated according to our task goals and expectations. In the current study, we conducted two experiments to compare and contrast neural mechanisms of selective attention related to searching for target items within perceptual versus VSTM representations. We used event-related potentials to investigate whether searching for relevant target items from within VSTM representations involves spatially specific biasing of neural activity in a manner analogous to that which occurs during visual search for target items in perceptual arrays. The results, replicated across the two experiments, revealed that selection of a target object within a search array maintained in VSTM proceeds through a similar mechanism as that in the perceptual domain. In line with previous results, N2pc potentials were obtained when targets were identified within a perceptual visual-search array. Interestingly, equivalent N2pcs, with similar time courses and scalp distributions, were also elicited when target items were identified within a VSTM representation. The findings reinforce the notion of highly flexible VSTM representations that can be modulated according to task goals and suggest a large degree of overlap in the spatially specific neural mechanisms of target selection across the perceptual and VSTM domains.
Many tasks in our daily life demand not only the use of different fingers of one hand in a serial... more Many tasks in our daily life demand not only the use of different fingers of one hand in a serial fashion, but also to alternate from one hand to the other. Here, we investigated performance in a bimanual serial reaction time task (SRTT) with particular emphasis on learning-related changes in reaction time (RT) for consecutive button presses for homologous index-and middle fingers. The bimanual SRTT consisted of sequential button presses either with the left or right index-and middlefinger to a series of visual letters displayed on a computer screen. Each letter was assigned a specific button press with one of four fingers. Two outcome measures were investigated: (a) global sequence learning as defined by the time needed to complete a 15-letter SRTT sequence and (b) changes in hand switch costs across learning. We found that bimanual SRTT resulted in a global decrease in RT during the time course of learning that persisted for at least two weeks. Furthermore, RT to a button press showed an increase when the previous button press was associated with another hand as opposed to the same hand. This increase in RT was defined as switch costs. Hand switch costs significantly decreased during the time course of learning, and remained stable over a time of approximately two weeks. This study provides evidence for modulations of switch costs during bimanual sequence learning, a finding that might have important implications for theories of bimanual coordination and learning.
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Papers by Joeran Lepsien