Past Projects

Completed projects

ABINEP M2-project 3: Modellierung Dopamin-induzierter neuronaler Netzwerk-Aktivität / "Learning conditional associations: rich temporal context and involvement of hippocampus / medial temporal lobe"
Duration: 01.05.2017 bis 30.03.2022

The international Graduate school (GS) on Analysis, Imaging, and Modelling of Neuronal and Inflammatory Processes (ABINEP) is based on the two internationally recognized biomedical research foci of the Otto-von-Guericke-University Magdeburg (OVGU), Neurosciences and Immunology. ABINEP aims at fostering cutting edge research projects in rising sub-disciplines of these research areas, which are currently supported by several German Research foundation (DFG)- and European Community (EU)-funded collaborative projects in Magdeburg (including the DFG-funded Collaborative Research Centers SFBs 779 and 854 and associated graduate schools, as well as DFG TRRs 31 and 62). The program includes scientists from the Medical Faculty/ University Hospital Magdeburg (MED) and the Faculty of Natural Sciences (FNW) of the OVGU, the Institute for Neurobiology (LIN) and German Center for Neurodegenerative Diseases (DZNE), both located in Magdeburg, the Helmholtz Centre of Infection Research in Braunschweig as well as international collaborators.

To further strengthen the international interconnection of these research foci, 21 projects were defined to educate excellent international PhD student candidates in any of the 4 ABINEP topical modules:
1) Neuroinflammation: Inflammatory processes in neurodegeneration
2) Neurophysiology and Computational Modelling of Neuronal Networks
3) Immunosenescence: Infection and immunity in the context of aging
4) Human Brain Imaging for diagnosing neurocognitive disorders

2) Neurophysiology and Computational Modelling of Neuronal Networks
Sport can activate protective mechanism which suppresses Dementia outbreaks. The detailed principles and possibilities to optimize therapies are not yet known. It is assumed that substances such as brain-derived neurotrophic factor (BDNF) and dopamine are mobilized in brains and increase synaptic plasticity processes and therefore to a delay in Dementia outbreaks. A systematical evaluation of the altered synaptic plasticity and the communication between different brain regions by BDNF and dopamine is currently missing and requires now scientific approaches. Computational modelling of neuronal networks should be used to predict the influence of pharmacological substances on the brain network activity and thereby the suppression of dementia outbreaks within animal models.

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INDIREA - Individualised Diagnostics and Rehabilitation of Attention
Duration: 01.09.2013 bis 31.08.2017

We propose a training network based around a linked set of research projects which attempt to improve the diagnosis and rehabilitation of neuropsychological disorders of attention, with each project linked to an external industrial partner in order to commercialise emerging diagnostic and rehabilitation procedures. New diagnostic procedures will link clinical measures of attentional disorders to a detailed mathematical account, which can in turn be linked to computational models of neuronal function. These behavioural measures will be integrated with brain imaging indices (using fMRI, EEG, MEG) to explain attentional disorders at a neural as well as a functional level. The emerging diagnostic procedures will be used to target individualised rehabilitation for patients, assessing effects of direct brain stimulation, EEG-based biofeedback, cognitive training of attention, and drug intervention. Each project will operate across both academic and industrial partners in the network, giving a unique commercial orientation to the training. Overall the project will advance neuropsychological diagnostics and rehabilitation, while giving trainees state-of-the-art inter-disciplinary research and entrepreneurial skills.

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Characterizing the precise dynamical balance of visual perception.”
Duration: 01.04.2014 bis 31.03.2017

The project aims to confirm and extend a novel approach to multi-stable perception. Superficially, the dynamics of multi-stable perception is highly diverse in different observers and in different situations but, fundamentally, it is consistent with a fine balance of competition, adaptation and noise, as our published preliminary work has shown. Several predictions flow from this observation, which the proposed project will test. 
The project combines detailed psychophysical observations of multi-stable perception (with more statistical measures than previous studies) in normal adults, as well as in adolescents and anorexia nervosa patients, with computational analyses to infer the precise dynamical operating regime of each individual. Specifically, we wish to test our central working hypothesis (precise balance of competition, adaptation, and noise) in four project parts: 
Part A: Do experimental manipulations of this balance shift the dynamical operating regime into the predicted direction? 
Part B: Does perceptual stability increase with decreasing sensitivity to input modulations (and vice versa), as computational theories of perception predict? 
Part C: Do the results of the computational analysis generalize to other mathematical formulations of the dynamical model?
Part D: Is the dynamical operating regime of diagnostic value, that is, does it reveal meaningful differences in the dynamical balance of different individuals? 
In fact, there are good theoretical reasons to expect visual perception – like any other process based on statistical inference – to operate in a precise dynamical balance. The larger significance of the proposed projects is threefold:  
It will establish whether or not the observed balance really is the balance predicted by theory, namely, a trade-off between the stability and the sensitivity of perceptual inference. 
It will establish whether or not the observed dynamical balance is generated by a multi-stable attractor dynamics (balance of competition, adaptation, and noise), rather than by some other mechanism generating itinerant dynamics. 
It will establish whether or not the precise dynamical balance of individual observers is of diagnostic value either over the course of development or in the context of neurological disorders. 
In conclusion, the proposed project will establish a novel, quantitative, and empirical method to test and refine important theoretical ideas such as the Bayesian brain hypothesis (Knill and Pouget, 2004) or the free-energy principle (Friston, 2010).

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Microsaccades as an objective index to visual orienting and selection
Duration: 01.04.2014 bis 31.03.2017

Our prior work has shown that microsaccades (MS) provide quantitative information not just about the direction and timing of attention shifts, but also about the location of continuously sustained attention. Recent work with non-human primates suggests that microsaccades reflect the activity of so-called visual selection neurons in a functionally integrated network of anatomically distributed brain areas (superior colliculus, frontal eye fields, lateral intraparietal area). This ‘selection map’ network is thought to integrate several aspects of visual orienting and selection, including top-down attention, bottom-up saliency, and saccade preparation.
We now propose a series of further human experiments to exploit the fact that micro saccades shadow these different aspects of orienting and selection. Specifically, we will combine our unmatched expertise in dual-task psychophysics with microsaccade observations and with computational modeling in order to characterize the interaction of top-down attention, bottom-up saliency, and saccade preparation in unprecedented detail.
The particular objectives of the proposed project are as follows:

The particular objectives of the proposed project are as follows:

Quantify the modulation of MS statistics by top-down visual attention, bottom-up visual saliency, and saccade planning.
Test the hypothesis that different orienting processes compete for a “limited resource”, the engagement of which is mirrored by MS statistics. 
Establish whether top-down and bottom-up selection modulate MS statistics in a comparable manner, as predicted by “saliency map” theories of visual attention .
Test the hypothesis that visual performance “outside the focus of attention” is associated with saliency-based modulations of MS statistics.
Clarify the much disputed relation between attention and discrimination performance (awareness) .
Model ‘selection map’ activity in a manner consistent with data from non-human primates (data from Dr. Hafed, Tübingen). Predict MS statistics from stochastic fluctuations in the model activity.
The proposed work with human observers will confirm and extend important findings from nonhuman primates. It will reveal how different aspects of visual orienting interact and are functionally integrated. It will test controversial theories of cognitive attention research – “limited capacity”, “saliency map”, relation to awareness – and may reveal their neurobiological basis in a ‘selection map’. Finally, the project will integrate all levels – perceptual performance, orienting states, fixational eye movements, and ‘selection map’ activity – in a compact computational framework, which in turn will generate numerous testable predictions.

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CORONET - Novel interfaces between brain and computer
Duration: 01.01.2011 bis 31.12.2014

Interfaces between the brain and electrical circuits in technical devices or computers open new perspectives for basic research and medical application, e.g., for therapeutic brain stimulation and neuroprosthetics. The new EU project CORONET will develop the technological and theoretical foundations for such future "bio-hybrid" interfaces between biological and artificial nervous tissues. 

The European Commission supports CORONET with 2.7 Mio. from the 7th Framework Program. Within the category "Brain-inspired Computing", CORONET received the best rating out of all 39 concurring project proposals. The key idea of CORONET is to work with, not against, the complex spontaneous activity of living nervous tissues. The project will first "gently steer" the spontaneous activity into a desired direction by applying continuous, weak electrical stimulation. Then, the nervous tissue will be coupled to artificial, electronic networks that show a behavior as complex as that of the living brain. By aid of this coupling, the scientists will try to "read out" natural, spontaneously arising activity states in the nervous tissue. 

In a first step, computer simulations will serve as artificial neural networks. In a second step, the researchers will apply custom-built advanced integrated circuits that operate based on principles of the brain ("neuromorphic VLSI"). The final goal of the project is to seamlessly interface "silicon-" and living nervous tissues.

The project involves senior scientists from Magdeburg, Dresden, Trieste, Rome, Haifa, and Barcelona and is led by Prof. Jochen Braun (Otto von Guericke University Magdeburg). It builds on previous research performed in the Bernstein Group Magdeburg, coordinated also by Prof. Braun and funded by the German Federal Ministry of Education and Research (BMBF).

Contact Information
Prof. Jochen Braun
Institut für Biologie 
Otto von Guericke University Magdeburg
Leipziger Str. 44 
39120 Magdeburg
Germany 
Phone: +49 391 67 55 050


more information
http://kobi.nat.uni-magdeburg.de - Cognitive Biology Group
http://www.bgcn.ovgu.de/ - Bernstein Group Magdeburg

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A short-term memory of multi-stable perception.
Duration: 07.11.2008 bis 07.11.2012

It is well known that pauses in the presentation of an ambiguous display may stabilize its perceptual appearance. Here we show that this stabilization depends on an extended history spanning several dominance periods, not merely on the most recent period. Specifically, appearance after a pause often reflects less recent (but longer) dominance periods rather than more recent (but shorter) periods. Our results imply the existence of a short-tem memory for perceptual appearance that builds up over seconds, decays over minutes, and is robust to perceptual reversals. Although this memory is most evident in paused displays, it influences perceptual reversals also when display presentation continues: while the memory of one appearance prevails over that of the other, successive dominance durations are positively correlated. This highly unusual successive dependence suggests that multi-stable perception is not the memoryless renewal process as which it has long been regarded. Instead, a short-term memory of appearance must be added to the multiple processes that jointly produce reversals of perceptual appearance.

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Cortical response to task-relevant stimuli outside the focus of attention.
Duration: 07.11.2008 bis 07.11.2012

Selective visual attention enhances the neural response to task-relevant visual items.  Responses to task-irrelevant and therefore presumably unattended items are not enhanced, or even suppressed relative to baseline. However, it is unknown what happens to items outside the focus of attention that are nevertheless relevant for the task at hand. We studied the retinotopic neural correlates of such processing with a dual-task fMRI-experiment. An attention-demanding central task was combined with one of two peripheral tasks concerning the same visual stimulus; one posing low and the other high attentional demands. Task-relevance increased BOLD-responses to the peripheral stimulus in the context of both task.  For the low-demand task, this increase was accompanied by good behavioral performance. For the high-demand task, performance remained near chance.  When the focus of attention was allowed to shift to the peripheral stimulus, neural responses increased even further. In a control experiment, we observed the differential persistence in iconic memory of visual attributes relevant to high- and low-demand tasks, respectively.  We conclude that, in the dual-task situation, the focus of attention initially remains on the central task, but subsequently shifts to the former location of the peripheral target.  This belated shift to an iconic memory explains the enhanced BOLD-response observed with both tasks.  Differential iconic persistence accounts for the disparate behavioral performance.   Our results suggest that attentional modulation, but not behavioral performance, is consistently associated with an enhanced BOLD-response.

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BMBF Bernstein Group "Components of Cognition: from small Networks to Flexible Rules" Bistable perception: neural representations at the bifurcation
Duration: 01.02.2007 bis 31.12.2010

Multi-stable perception is not the "memoryless" process as which it was long regarded. Recent psychophysical studies reveal both stabilizing and destabilizing effects of perceptual history: the recent experience of a particular percept makes it both more likely (in the short run) and less likely (in the long run) to experience the same percept again. The destabilizing effect presumably reflects some form of adaptation (either neuronal or synaptic). Surprisingly, the destabilizing effect does not seem to actually cause perceptual reversals. Rather, reversals appear to be noise-driven. Cumulative measures of the destabilizing effect reveal only a limited control over reversals. When the cumulative measures of competing percepts are balanced, perception enters transitional states in which neither percept dominates. A competitive network of biophysically realistic neurons replicates this behaviour only when it resides just next to the bifurcation between an adaptation driven regime (limit cycle) and a noise driven regime (metastability). There are a number of ecological and functional reasons why perceptual representations should be established at this bifurcation point.

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BMBF Bernstein Group "Components of cognition: from small networks to flexible rules" Individual configurability of plastic synapses in neuromorphic VLSI
Duration: 01.02.2007 bis 31.12.2010

The pioneering work of C. Mead \cite{Mead89} has introduced the term ``neuromorphic engineering'' for a growing family of analog, sub-threshold circuits, which implement the accepted equivalent circuits of biological neurons and synapses in VLSI technology. The ultimate aim of neuromorphic engineering is to mimic the capabilities of biological perception and information processing with a compact and energy-efficient platform. We believe that this goal necessitates from the outset some mechanism of ``learning" that enables neuromorphic devices to adapt (or re-configure) themselves while interacting with an environment. Emulating the example of biological neurons and synapses, our neuromorphic devices attain an ability for "learning" by incorporating ``Hebbian-like" mechanisms of synaptic plasticity. In the "Hebbian" scenario, the efficacy of a synapse is enhanced (i.e., its impact on the post-synaptic neuron is increased), when the activities of pre- and post-synaptic neurons are correlated on a suitable time-scale, and reduced if the activities are anti-correlated on this time-scale. Whether ``Hebbian" learning is based on average firing rates or on individual spikes (``spike-time-dependent plasticity", or STDP) is a matter of continuing debate and a choice that strongly influences alternative designs of neuromorphic synapse circuits. The synaptic circuits described here represent a compromise, in that they combine rate-based ``Hebbian" learning with many aspects of STDP. We illustrate tests and measurements performed on an analog, VLSI chip implementing 128 integrate-and-fire (IF) neurons and 16,384 plastic synapses. Each synapse may be individually configured to be either excitatory or inhibitory and to receive either recurrent input from an on-chip neuron or AER-based input from an off-chip neuron.

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European Summer School "Visual Neuroscience: from Spikes to Awareness"
Duration: 01.01.2006 bis 31.12.2010

Bereits zum vierten Mal findet die zweiwöchige Internationale Sommerschule Visuelle Neurowissenschaften statt, die vom Marburger Neurophysiker, Professor Dr. Frank Bremmer, zusammen mit seinen wissenschaftlichen Kollegen Professor Dr. Karl Gegenfurtner (Gießen) und Professor Dr. Jochen Braun (Magdeburg) organisiert wird. Bereits der ersten Sommerschule im September 2004 ebenfalls auf Schloss Rauischholzhausen bescheinigt Bremmer einen unerwartet großen Erfolg .
Wie in den Vorjahren gingen 2010 fast 200 hochkarätige Bewerbungen aus aller Welt ein, aus denen die 30 Besten ausgewählt wurden. Auch die Sprecher sind wieder international höchst anerkannte Spitzenforscher, unter ihnen der diesjährige Leibniz-Preisträger und Direktor des Deutschen Primatenzentrums, Professor Dr. Stefan Treue, und der diesjährige Champalimaud Award Winner, Professor Dr. Anthony Movshon, von der New York University. Bremmer und seine Kollegen sind von dem Erfolg der diesjährigen Veranstaltung und der Euphorie der Teilnehmer so motiviert, dass sie versuchen werden, daraus eine ständige Einrichtung im zweijährigen Abstand werden zu lassen. Die Sommerschule wäre damit ein Gegenpol zu renommierten Veranstaltungen in den USA, zum Beispiel Cold Spring Harbor.

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NIMITEK Consistent temporal order speeds association learning: reinforcement learning
Duration: 01.01.2005 bis 31.12.2009

Why are unrelated associations learned more rapidly in a consistent temporal order? Observers viewed highly distinguishable, fractal objects and learned by trial and error to respond to each object with a particular motor response (one of four). In five experiments, associations between visual objects and motor responses were learned more rapidly for objects presented in a consistent temporal order (i.e., objects with consistent predecessor objects). Incremental learning of action weights for current and past objects does not account for the observed effects of temporal order ( direct actor ). However, a modified model with differential learning rates for current and past objects agrees qualitatively with observations. In the modified reinforcement model, a Kalman filter quantifies the certainty with which past observations predict future rewards and adjusts learning rates accordingly (Sutton, 1992, Proceedings of the 7^th Yale Workshop on Adaptive and Learning Systems, pp. 161-166). But does reinforcement learning of additional action weights truly capture the essence of the temporal order effects? We also consider an alternative view, according to which consistent temporal order eases the recognition problem posed by unfamiliar fractal objects.

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Bistable Perception Modeled as Competing
Duration: 01.01.2003 bis 31.12.2007

We propose stochastic integration at two neural levels as a model for bistable perception. In this model, two sets of meta-stable populations are driven by visual input, while two further sets are driven by the phenomenal percept. A perceptual reversal occurs whenever the activity associated with one percept exceeds a threshold. Perceptual alternations result from the continuous repetition of this race to threshold. Our model accounts for several hitherto puzzling aspects of bistable perception: the wide range of alternation rates observed under different conditions, the highly consistent statistics, the perceptual stabilization with interrupted displays, and the history-dependence of phenomenal appearance. It also predicts details of the dynamics of bistable perception that have so far not been examined. We conclude that bistable perception reflects the collective nature of neural decision making, rather than specific biophysical properties of individual neurons.

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