BCCN Tübingen - News

Bernstein Conference Tuebingen: Abstract submission open!

Wed, 03 Apr 2013 16:19:00 +0200

Visit www.bernstein-conference.de for more information.

Changing the responses of cortical neurons from sub- to suprathreshold using single spikes in vivo

Mon, 21 Jan 2013 14:01:00 +0100

Nerve cells, called neurons, are one of the core components of the brain and form complex networks by connecting to other neurons via long, thin ‘wire-like’ processes called axons. Axons can extend across the brain, enabling neurons to form connections—or synapses—with thousands of others. It is through these complex networks that incoming information from sensory organs, such as the eye, is propagated through the brain and encoded.

The basic unit of communication between neurons is the action potential, often called a ‘spike’, which propagates along the network of axons and, through a chemical process at synapses, communicates with the postsynaptic neurons that the axon is connected to. These action potentials excite the neuron that they arrive at, and this excitatory process can generate a new action potential that then propagates along the axon to excite additional target neurons. In the visual areas of the cortex, neurons respond with action potentials when they ‘recognize’ a particular feature in a scene—a process called tuning. How a neuron becomes tuned to certain features in the world and not to others is unclear, as are the rules that enable a neuron to change what it is tuned to. What is clear, however, is that to understand this process is to understand the basis of sensory perception.

Memory storage and formation is thought to occur at synapses. The efficiency of signal transmission between neurons can increase or decrease over time, and this process is often referred to as synaptic plasticity. But for these synaptic changes to be transmitted to target neurons, the changes must alter the number of action potentials. Although it has been shown in vitro that the efficiency of synaptic transmission—that is the strength of the synapse—can be altered by changing the order in which the pre- and postsynaptic cells are activated (referred to as 'Spike-timing-dependent plasticity'), this has never been shown to have an effect on the number of action potentials generated in a single neuron in vivo. It is therefore unknown whether this process is functionally relevant.

Now Pawlak et al. report that spike-timing-dependent plasticity in the visual cortex of anaesthetized rats can change the spiking of neurons in the visual cortex. They used a visual stimulus (a bar flashed up for half a second) to activate a presynaptic cell, and triggered a single action potential in the postsynaptic cell a very short time later. By repeatedly activating the cells in this way, they increased the strength of the synaptic connection between the two neurons. After a small number of these pairing activations, presenting the visual stimulus alone to the presynaptic cell was enough to trigger an action potential (a suprathreshold response) in the postsynaptic neuron—even though this was not the case prior to the pairing.

This study shows that timing rules known to change the strength of synaptic connections—and proposed to underlie learning and memory—have functional relevance in vivo, and that the timing of single action potentials can change the functional status of a cortical neuron. Original publication:

Pawlak V., Greenberg D.S., Sprekeler H., Gerstner W., Kerr J.N.D. (2013). Changing the responses of cortical neurons from sub- to suprathreshold using single spikes in vivo. eLife Sciences 2013;2:e00012. Contact:
Dr. Jason Kerr
Max Planck Institut for Biological Cybernetics
Spemannstr. 41
email: jason@tuebingen.mpg.de
Phone: +49 7071 601-1792

Who decides in the brain?

Tue, 15 Jan 2013 12:31:00 +0100

Whether in society or nature, decisions are often the result of complex interactions between many factors. Because of this it is usually difficult to determine how much weight the different factors have in making a final decision. Neuroscientists face a similar problem since decisions made by the brain always involve many neurons. Within a collaboration of the University of Tübingen and the Max Planck Institute for Biological Cybernetics, supported within the framework of the Bernstein Network, researchers lead by CIN professor Matthias Bethge have now shown how the weight of individual neurons in the decision-making process can be reconstructed despite interdependencies between the neurons.

When we see a person on the other side of the street who looks like an old friend, the informational input enters the brain via many sensory neurons. But which of these neurons are crucial in passing on the relevant information to higher brain areas, which will decide who the person is and whether to wave and say 'hello'? A research group lead by Matthias Bethge has now developed an equation that allows us to calculate to what degree a given individual sensory neuron is involved in the decision process. To approach this question, experimental researchers have so far considered the information that an individual sensory neuron carries about the final decision. Just as an individual is considered suspicious if he or she is found to have insider information about a crime, those sensory neurons whose activity contains information about the eventual decision are presumed to have played a role in reaching the final decision. The problem with this approach is that neurons - much like people – are constantly communicating with each other. A neuron which itself is not involved in the decision may simply have received this information from a neighboring neuron, and “join the conversation”. Actually, the neighboring cell sends out the crucial signal transmitted to the higher decision areas in the brain. The new formula that has been developed by scientists addresses this by accounting not just for the information in the activity of any one neuron but also for the communication that takes place between them. This formula will now be used to determine whether only a few neurons that carry a lot of information are involved in the brain's decision process, or whether the information contained in very many neurons gets combined. In particular, it will be possible to address the more fundamental question: In which decisions does the brain use information in an optimal way, and for which decisions is its processing suboptimal? The National Bernstein Network Computational Neuroscience was initiated by the Ministry for Education and Research (BMBF) in 2004 in order to establish the research discipline Computational Neuroscience in Germany. With the support of the BMBF, the network has developed into one of the largest research networks in the field of Computational Neuroscience worldwide. Namesake of the network is the German physiologist Julius Bernstein (1835-1917). The Werner Reichardt Centre for Integrative Neuroscience (CIN) is an interdisciplinary institution at the Eberhard Karls University Tübingen funded by the German Excellence Initiative program. Its aim is to deepen our understanding of how the brain generates function and how brain diseases impair them, guided by the conviction that any progress in understanding can only be achieved through an integrative approach spanning multiple levels of organization. © Mareike Kardinal, Ralf Haefner Original publication: Haefner R.M., Gerwinn S., Macke J.H., Bethge M. (2013): „Inferring decoding strategies from choice probabilities in the presence of correlated variability“. Nature Neuroscience: Jan 13, 2013 http://dx.doi.org/10.1038/nn.3309 Contact: Dr. Ralf Haefner
Volen National Center for Complex Systems,
Volen 208/MS 013,
Brandeis University,
Waltham, MA 02454 (USA)
eMail: ralf@brandeis.edu
Tel: +1 (781) 786 1683 Prof. Dr. Matthias Bethge
Werner Reichardt Center for Integrative Neurosciences
University of Tübingen
Max Planck Institute for Biological Cybernetics
Bernstein Center for Computational Neuroscience
Otfried-Müllerstr. 25
72076 Tübingen (Germany)
eMail: matthias@bethgelab.org
Tel: +49 (0)7071-29 89017

3D Reconstruction and Standardization of the Rat Vibrissal Cortex for Precise Registration of Single Neuron Morphology

Mon, 07 Jan 2013 18:04:00 +0100

Abstract:
The three-dimensional (3D) structure of neural circuits is commonly studied by reconstructing individual or small groups of neurons in separate preparations. Investigation of structural organization principles or quantification of dendritic and axonal innervation thus requires integration of many reconstructed morphologies into a common reference frame. Here we present a standardized 3D model of the rat vibrissal cortex and introduce an automated registration tool that allows for precise placement of single neuron reconstructions. We (1) developed an automated image processing pipeline to reconstruct 3D anatomical landmarks, i.e., the barrels in Layer 4, the pia and white matter surfaces and the blood vessel pattern from high-resolution images, (2) quantified these landmarks in 12 different rats, (3) generated an average 3D model of the vibrissal cortex and (4) used rigid transformations and stepwise linear scaling to register 94 neuron morphologies, reconstructed from in vivo stainings, to the standardized cortex model. We find that anatomical landmarks vary substantially across the vibrissal cortex within an individual rat. In contrast, the 3D layout of the entire vibrissal cortex remains remarkably preserved across animals. This allows for precise registration of individual neuron reconstructions with approximately 30 mm accuracy. Our approach could be used to reconstruct and standardize other anatomically defined brain areas and may ultimately lead to a precise digital reference atlas of the rat brain. Original publication:
Egger R, Narayanan RT, Helmstaedter M, de Kock CPJ, Oberlaender M (2012) 3D Reconstruction and Standardization of the Rat Vibrissal Cortex for Precise Registration of Single Neuron Morphology. PLoS Comput Biol 8(12): e1002837. doi:10.1371/journal.pcbi.1002837

The end of a dogma: Bipolar cells generate action potentials

Thu, 13 Dec 2012 14:08:00 +0100

To make information transmission to the brain reliable, the retina first has to “digitize” the image. Until now, it was widely believed that this step takes place in the retinal ganglion cells, the output neurons of the retina. Scientists in the lab of Thomas Euler at the University of Tübingen, the Werner Reichardt Centre for Integrative Neuroscience and the Bernstein Center Tübingen were now able to show that already bipolar cells can generate “digital” signals. At least three types of mouse BC showed clear evidence of fast and stereotypic action potentials, so called “spikes”. These results show that the retina is by no means as well understood as is commonly believed.

The retina in our eyes is not just a sheet of light sensors that – like a camera chip – faithfully transmits patterns of light to the brain. Rather, it performs complex computations, extracting several features from the visual stimuli, e.g., whether the light intensity at a certain place increases or decreases, in which direction a light source moves or whether there is an edge in the image. To transmit this information reliably across the optic nerve - acting as a kind of a cable - to the brain, the retina reformats it into a succession of stereotypic action potentials – it “digitizes” it. Classical textbook knowledge holds that this digital code – similar to the one employed by computers – is applied only in the retina’s ganglion cells, which send the information to the brain. Almost all other cells in the retina were believed to employ graded, analogue signals. But the Tübingen scientists could now show that, in mammals, already the bipolar cells, which are situated right after the photoreceptors within the retinal network, are able to work in a “digital mode” as well.

Using a new experimental technique, Tom Baden and colleagues recorded signals in the synaptic terminals of bipolar cells in the mouse retina. Based on the responses of these cells to simple light stimuli, they were able to separate the neurons into eight different response types. These types closely resembled those expected from physiological and anatomical studies. But surprisingly, the responses of the fastest cell types looked quite different than expected: they were fast, stereotypic and occurred in an all-or-nothing instead of a graded fashion. All these are typical features of action potentials. Such “digital” signals had occasionally been observed in bipolar cells before, but these were believed to be rare exceptional cases. Studies from the past two years on the fish retina had already cast doubt on the long-held belief that BCs do not spike. The new data from Tübingen clearly show that these “digital” signals are systematically generated in certain types of mammalian bipolar cells. Action potentials allow for much faster and temporally more precise signal transmission than graded potentials, thus offering advantages in certain situations. The results from Tübingen call a widely held dogma of neuroscience into question - and open up many new questions.

The Bernstein Center Tübingen is part of the National Bernstein Network Computational Neuroscience in Germany. With this funding initiative, the German Federal Ministry of Education and Research (BMBF) supports the new discipline of Computational Neuroscience since 2004 with over 150 Mio. €. The network is named after the German physiologist Julius Bernstein (1835–1917).

Original Publication:
Baden T., Berens P., Bethge M., Euler T. (2012): „Spikes in Mammalian Bipolar Cells Support Temporal Layering of the Inner Retina“. Current Biology: Dec 13, 2012 , doi: 10.1016/j.cub.2012.11.006

Contact:
Dr. Tom Baden
Eberhard Karls Universität Tübingen
Werner Reichardt Centre for Integrative Neuroscience (CIN) / Institute for Ophthalmic Research
Otfried-Mueller-Strasse 25
72076 Tuebingen
Phone: +49 (0)7071 29 84749
thomas.baden@uni-tuebingen.de

Prof. Thomas Euler
Eberhard Karls Universität Tübingen
Werner Reichardt Centre for Integrative Neuroscience (CIN) / Institute for Ophthalmic Research
Otfried-Mueller-Strasse 25
72076 Tuebingen
Phone: +49 (0)7071 29 85028
thomas.euler@cin.uni-tuebingen.de

Eberhart Zrenner awarded for his lifetime achievements.

Thu, 26 Jul 2012 16:12:00 +0200

Eberhart Zrenner was honored for his lifetime achievements. His work is dedicated to the research of the causes of hereditary blindness-causing retina degeneration and the development of novel therapies. In a long series of world-renowned eye researchers, he is the first German who has been selected for the biennial prize by an international jury. The award funded by the Ludwig and Henrietta von Sallmann Foundation comes with a prize money of $ 35,000 and has been awarded at the "International Society for Eye Research" meeting in Berlin on July 25, 2012.

Bernhard Schoelkopf awarded with the Academy Prize 2012

Wed, 27 Jun 2012 09:31:00 +0200

In the "Empirical Inference" department headed by Bernhard Schoelkopf new learning algorithms are developed to detect structures in various sorts of data. The methods include causal inference, pattern recognition, regression, density estimation, novelty detection and feature selection.

Bernhard Schoelkopf is managing director of the newly founded Max Planck Institute for Intelligent Systems located in Tübingen and Stuttgart.

Read more in the press releases (only german):
Academy of Sciences and Humanities of Berlin-Brandenburg
Max Planck Institute for Intelligent Systems

Max Planck Society awards Otto Hahn Medal to Dr. Jakob Macke

Mon, 18 Jun 2012 16:21:00 +0200

Jakob Macke, who joined the BCCN Tübingen as Junior Research Group Leader in May 2012, received an Otto Hahn Medal of the Max Planck Society in recognition of his outstanding doctoral thesis entitled "Population coding in the visual system: Statistical methods and theory". Dr. Macke studied Mathematics at Oxford University before performing his graduate research under the supervision of Prof. Matthias Bethge at the Max Planck Institute for Biological Cybernetics in Tübingen. In his graduate research, he developed a mathematical analysis which provides a deeper understanding of the statistical structure of activity pattern of large neural populations, and explained several seemingly contradicting experimental observations based on multi-cell recordings of neural activity.

After his PhD, Jakob Macke worked together with Dr. Maneesh Sahani at the Gatsby Computational Neuroscience Unit, University College London, as a Marie Curie Fellow and developed new data analysis techniques for unravelling the influence of the intrinsic cortical dynamics on neural coding. He recently establish the group "Neural Computation and Behaviour" at the Bernstein Center for Computational Neuroscience Tübingen and the Max Planck Institut for Biological Cybernetics. The goal of the group is to obtain a better understanding of how internal states influence neural information processing and observed behaviour. To this end, the group will develop statistical methods for modelling measurements of neural activity and behaviour, and will collaborate closely with experimental laboratories at the Center.

The Max Planck Society has honoured up to 30 young scientists and researchers each year with the Otto Hahn Medal for outstanding scientific achievements since 1978. The award comes with a monetary sum of 7500 euros as recognition, and was conferred at the Annual General Assembly of the Max Planck Society in Düsseldorf on June 13, 2012.

Tübingen Placed Among Germany’s Elite Universities

Mon, 18 Jun 2012 08:00:00 +0200

In addition to the approval of the already existing Excellence Cluster for Integrative Neuroscience (CIN), Tübingen is now placed among Germany’s Elite Universities with a new Graduate School in the field of Empirical Education Research. These areas and the University will now receive considerable funding from the German Research Foundation, the DFG. See press release of the university for more details.

The European Vision Award 2012 goes to Prof. Frank Schaeffel

Wed, 13 Jun 2012 09:40:00 +0200

As to Frank Schaeffel’s contribution to the research field of refractive development and myopia there are few who can claim to have made such an influence on this research community over the last 30 years. Frank Schaeffel’s classic paper regarding “ accommodation, refractive error and eye growth in chickens” in 1998 produced a paradigm shift in our understanding of regulation of refractive errors and ocular growth. While this is one of the most cited papers in the area (2nd only to Nobel Laureate Torsten Wiesel, who with Elio Raviola published an important early paper in 1977 on the monkey model of myopia), it is Frank Schaeffel’s continued and numerous contributions to the research field of myopia over the last 25 years, which marks him out for special recognition. The price will be presented on October 11th, 2012 during der EVER conference in Nice, where Frank Schaeffel will give a talk entitled "From chickens to human - learning about the puzzles of myopia".