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Maass A.,Otto Von Guericke University of Magdeburg | Schutze H.,Otto Von Guericke University of Magdeburg | Speck O.,Otto Von Guericke University of Magdeburg | Speck O.,German Center for Neurodegenerative Diseases | And 17 more authors.
Nature Communications | Year: 2015

The ability to form long-term memories for novel events depends on information processing within the hippocampus (HC) and entorhinal cortex (EC). The HC-EC circuitry shows a quantitative segregation of anatomical directionality into different neuronal layers. Whereas superficial EC layers mainly project to dentate gyrus (DG), CA3 and apical CA1 layers, HC output is primarily sent from pyramidal CA1 layers and subiculum to deep EC layers. Here we utilize this directionality information by measuring encoding activity within HC/EC subregions with 7T high resolution functional magnetic resonance imaging (fMRI). Multivariate Bayes decoding within HC/EC subregions shows that processing of novel information most strongly engages the input structures (superficial EC and DG/CA2-3), whereas subsequent memory is more dependent on activation of output regions (deep EC and pyramidal CA1). This suggests that while novelty processing is strongly related to HC-EC input pathways, the memory fate of a novel stimulus depends more on HC-EC output. © 2014 Macmillan Publishers Limited. All rights reserved.

Maass A.,Otto Von Guericke University of Magdeburg | Maass A.,German Center for Neurodegenerative Diseases | Berron D.,Otto Von Guericke University of Magdeburg | Berron D.,German Center for Neurodegenerative Diseases | And 6 more authors.
eLife | Year: 2015

The entorhinal cortex (EC) is the primary site of interactions between the neocortex and hippocampus. Studies in rodents and nonhuman primates suggest that EC can be divided into subregions that connect differentially with perirhinal cortex (PRC) vs parahippocampal cortex (PHC) and with hippocampal subfields along the proximo-distal axis. Here, we used high-resolution functional magnetic resonance imaging at 7 Tesla to identify functional subdivisions of the human EC. In two independent datasets, PRC showed preferential intrinsic functional connectivity with anterior-lateral EC and PHC with posterior-medial EC. These EC subregions, in turn, exhibited differential connectivity with proximal and distal subiculum. In contrast, connectivity of PRC and PHC with subiculum followed not only a proximal-distal but also an anterior-posterior gradient. Our data provide the first evidence that the human EC can be divided into functional subdivisions whose functional connectivity closely parallels the known anatomical connectivity patterns of the rodent and nonhuman primate EC. © Maass et al.

Scheidegger M.,ETH Zurich | Scheidegger M.,University of Zürich | Walter M.,Otto Von Guericke University of Magdeburg | Walter M.,Leibniz Institute for Neurobiology | And 13 more authors.
PLoS ONE | Year: 2012

Increasing preclinical and clinical evidence underscores the strong and rapid antidepressant properties of the glutamate-modulating NMDA receptor antagonist ketamine. Targeting the glutamatergic system might thus provide a novel molecular strategy for antidepressant treatment. Since glutamate is the most abundant and major excitatory neurotransmitter in the brain, pathophysiological changes in glutamatergic signaling are likely to affect neurobehavioral plasticity, information processing and large-scale changes in functional brain connectivity underlying certain symptoms of major depressive disorder. Using resting state functional magnetic resonance imaging (rsfMRI), the "dorsal nexus "(DN) was recently identified as a bilateral dorsal medial prefrontal cortex region showing dramatically increased depression-associated functional connectivity with large portions of a cognitive control network (CCN), the default mode network (DMN), and a rostral affective network (AN). Hence, Sheline and colleagues (2010) proposed that reducing increased connectivity of the DN might play a critical role in reducing depression symptomatology and thus represent a potential therapy target for affective disorders. Here, using a randomized, placebo-controlled, double-blind, crossover rsfMRI challenge in healthy subjects we demonstrate that ketamine decreases functional connectivity of the DMN to the DN and to the pregenual anterior cingulate (PACC) and medioprefrontal cortex (MPFC) via its representative hub, the posterior cingulate cortex (PCC). These findings in healthy subjects may serve as a model to elucidate potential biomechanisms that are addressed by successful treatment of major depression. This notion is further supported by the temporal overlap of our observation of subacute functional network modulation after 24 hours with the peak of efficacy following an intravenous ketamine administration in treatment-resistant depression. © 2012 Scheidegger et al.

Wagenbreth C.,Otto Von Guericke University of Magdeburg | Zaehle T.,Otto Von Guericke University of Magdeburg | Galazky I.,Otto Von Guericke University of Magdeburg | Voges J.,Otto Von Guericke University of Magdeburg | And 8 more authors.
Journal of Neurology | Year: 2015

Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment for motor impairments in Parkinson’s disease (PD) but its effect on the motivational regulation of action control is still not fully understood. We investigated whether DBS of the STN influences the ability of PD patients to act for anticipated reward or loss, or whether DBS improves action execution independent of motivational valence. 16 PD patients (12 male, mean age = 58.5 ± 10.17 years) treated with bilateral STN-DBS and an age- and gender-matched group of healthy controls (HC) performed a go/no-go task whose contingencies explicitly decouple valence and action. Patients were tested with (ON) and without (OFF) active STN stimulation. For HC, there was a benefit in performing rewarded actions when compared to actions that avoided punishment. PD patients showed such a benefit reliably only when STN stimulation was ON. In fact, the relative behavioral benefit for go for reward over go to avoid losing was stronger in the PD patients under DBS ON than in HC. In PD patients, rather than generally improving motor functions independent of motivational valence, modulation of the STN by DBS improves action execution specifically when rewards are anticipated. Thus, STN-DBS establishes a reliable congruency between action and reward (“Pavlovian congruency”) and remarkably enhances it over the level observed in HC. © 2015, Springer-Verlag Berlin Heidelberg.

Lord A.,Queensland Institute of Medical Research | Lord A.,University of Queensland | Horn D.,Leibnitz Institute for Neurobiology | Horn D.,Otto Von Guericke University of Magdeburg | And 7 more authors.
PLoS ONE | Year: 2012

Major depression is a prevalent disorder that imposes a significant burden on society, yet objective laboratory-style tests to assist in diagnosis are lacking. We employed network-based analyses of "resting state" functional neuroimaging data to ascertain group differences in the endogenous cortical activity between healthy and depressed subjects. We additionally sought to use machine learning techniques to explore the ability of these network-based measures of resting state activity to provide diagnostic information for depression. Resting state fMRI data were acquired from twenty two depressed outpatients and twenty two healthy subjects matched for age and gender. These data were anatomically parcellated and functional connectivity matrices were then derived using the linear correlations between the BOLD signal fluctuations of all pairs of cortical and subcortical regions. We characterised the hierarchical organization of these matrices using network-based matrics, with an emphasis on their mid-scale "modularity" arrangement. Whilst whole brain measures of organization did not differ between groups, a significant rearrangement of their community structure was observed. Furthermore we were able to classify individuals with a high level of accuracy using a support vector machine, primarily through the use of a modularity-based metric known as the participation index. In conclusion, the application of machine learning techniques to features of resting state fMRI network activity shows promising potential to assist in the diagnosis of major depression, now suggesting the need for validation in independent data sets. © 2012 Lord et al.

Bonath B.,Otto Von Guericke University of Magdeburg | Noesselt T.,Otto Von Guericke University of Magdeburg | Noesselt T.,Center for Behavioral and Brain science | Krauel K.,Otto Von Guericke University of Magdeburg | And 3 more authors.
NeuroImage | Year: 2014

An essential task of our perceptual systems is to bind together the distinctive features of single objects and events into unitary percepts, even when those features are registered in different sensory modalities. In cases where auditory and visual inputs are spatially incongruent, they may still be perceived as belonging to a single event at the location of the visual stimulus - a phenomenon known as the 'ventriloquist illusion'. The present study examined how audio-visual temporal congruence influences the ventriloquist illusion and characterized its neural underpinnings with functional magnetic resonance imaging (fMRI). Behaviorally, the ventriloquist illusion was reduced for asynchronous versus synchronous audio-visual stimuli, in accordance with previous reports. Neural activity patterns associated with the ventriloquist effect were consistently observed in the planum temporale (PT), with a reduction in illusion-related fMRI-signals ipsilateral to visual stimulation for central sounds perceived peripherally and a contralateral increase in illusion-related fMRI-signals for peripheral sounds perceived centrally. Moreover, it was found that separate but adjacent regions within the PT were preferentially activated for ventriloquist illusions produced by synchronous and asynchronous audio-visual stimulation. We conclude that the left-right balance of neural activity in the PT represents the neural code that underlies the ventriloquist illusion, with greater activity in the cerebral hemisphere contralateral to the direction of the perceived shift of sound location. © 2014 Elsevier Inc.

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