BCCN Tübingen - News

Two new junior research groups at the BCCN Tuebingen

Fri, 27 Apr 2012 11:53:00 +0200

Jakob Macke's research agenda aims at getting a better understanding of cortical coding principles that take into account the influence of the internal dynamics of cortical processing using probabilistic modelling techniques and machine learning algorithms. In particular, the goal is to explain a substantial fraction of the large trial-to-trial variability found neural activity and animal behaviour.

The research program of Marcel Oberlaender focuses on reconstructing the 3D structure of neural circuits and using these anatomically realistic network models to study the signal flow underlying perception and behavior. In particular, he develops detailed models of cell type-specific circuits in the rodent vibrissal cortex which elucidate structural and functional mechanistic principles underlying sensory-evoked information processing.

Computational Vision Summer School 2012

Mon, 12 Mar 2012 10:53:00 +0100

Upcoming Conferences in September

Tue, 06 Mar 2012 10:14:00 +0100

Sensory Coding and Natural Environment 2012, September 9th - 12th, Klosterneuburg, Austria
INCF 2012, September 10th - 12th, Munich
BCCN 2012, September 12th - 14th, Munich

Multisensory integration: when correlation implies causation.

Thu, 15 Dec 2011 18:00:00 +0100

In order to get a better picture of our surroundings, the brain has to integrate information from different senses, but how does it know which signals to combine? New research involving scientists from the Max Planck Institute for Biological Cybernetics, the Bernstein Center for Computational Neuroscience Tübingen, the University of Oxford, and the University of Bielefeld has demonstrated that humans exploit the correlation between the temporal structures of signals to decide which of them to combine and which to keep segregated. This research is about to be published in Current Biology. Multisensory signals originating from the same distal event are often similar in nature. Think of fireworks on New Year’s Eve, an object falling and bouncing on the floor, or the footsteps of a person walking down the street. The temporal structures of such visual and auditory events are always almost overlapping (i.e., they correlate), and we often effortlessly assume an underlying unity between our visual and auditory experiences. In fact, the similarity of temporal structure of multiple unisensory signals, rather than merely their temporal coincidence as it has been previously thought, provides a potentially powerful cue for the brain to determine whether or not multiple sensory signals have a common cause. Cesare Parise from the Max Planck Institute for Biological Cybernetics in Tübingen and Bernstein Center for Computational Neuroscience Tübingen and his colleagues set out to examine the role of signal correlation in multisensory integration by asking people to localize a stream of beeps and flashes. Participants seated in front of a large screen where sounds (streams of noise bursts) and images (streams blurred blobs) were presented from different spatial locations. On some trials only visual or auditory stimuli were presented, while on other trials visual and auditory stimuli were presented in combination. Critically, on combined audiovisual trials, the temporal structure of the visual and auditory stimuli could either be correlated or not. Participants were required to report the spatial position of such stimuli by moving a cursor controlled by a graphic tablet. In line with previous studies, participants were more precise when the auditory and visual streams were presented together than when they were presented in isolation. Notably, precision was even higher when auditory and visual streams were correlated, and closely approached the theoretical maximum. These results demonstrate that humans optimally combine multiple sensory signals only when they correlate in time. Previous research has demonstrated that optimal integration only occurs when the brain is sure that the signals have a common underlying cause. These results therefore demonstrate that the brain uses the statistical correlation between the sensory signals to infer whether they have a common physical cause, and hence whether they provide redundant information that should be integrated. The researchers suggest the brain has evolved this ability to combine potentially related information from different senses so it can effectively pick its way through the noisy environments of everyday life. “It’s why at a noisy cocktail party you can tell who is speaking with which voice,” says Parise. “Our eyes and ears are continually taking in sensory information and our brains make sense of it all by merging together sights and sounds with similar temporal structures.” In spite of being a pervasive aspect of sensory processing, little is known about the low-level statistical determinants of multisensory integration for signals with complex dynamic temporal patterns. This research highlights the role of a key organizational principle for multisensory perceptual grouping. What at first glance appears to be a logical fallacy, namely inferring causation from correlation, turns out to be the rule in perception.

Original Publication:
Cesare V. Parise, Charles Spence, Marc O. Ernst: When Correlation Implies Causation in Multisensory Integration. Current Biology doi: 10.1016/j.cub.2011.11.039 © Cesare Parise & Public relations office Max Planck Campus Tuebingen Photo: © Jochen Kopp/Uni Bielefeld und Cesare Parise/MPI für biologische Kybernetik Contact:
Cesare Parise
Max Planck Institute for Biological Cybernetics
Bernstein Center for Computational Neuroscience Tübingen
Phone: +49 521 106-5703
E-mail: cesare.parise@tuebingen.mpg.de

Bernstein Newsletter Edition December 2011

Fri, 09 Dec 2011 18:00:00 +0100

The new edition December 2011 of the Bernstein newsletter is available in english and german.

Estimation of 3D shape from image orientations

Tue, 06 Dec 2011 15:27:00 +0100

Abstract:
One of the main functions of vision is to estimate the 3D shape of objects in our environment. Many different visual cues, such as stereopsis, motion parallax, and shading, are thought to be involved. One important cue that remains poorly understood comes from surface texture markings. When a textured surface is slanted in 3D relative to the observer, the surface patterns appear compressed in the retinal image, providing potentially important information about 3D shape. What is not known, however, is how the brain actually measures this information from the retinal image. Here, we explain how the key information could be extracted by populations of cells tuned to different orientations and spatial frequencies, like those found in the primary visual cortex. To test this theory, we created stimuli that selectively stimulate such cell populations, by “smearing” (filtering) images of 2D random noise into specific oriented patterns. We find that the resulting patterns appear vividly 3D, and that increasing the strength of the orientation signals progressively increases the sense of 3D shape, even though the filtering we apply is physically inconsistent with what would occur with a real object. This finding suggests we have isolated key mechanisms used by the brain to estimate shape from texture. Crucially, we also find that adapting the visual system's orientation detectors to orthogonal patterns causes unoriented random noise to look like a specific 3D shape. Together these findings demonstrate a crucial role of orientation detectors in the perception of 3D shape. Original publication:
Roland W. Fleming, Daniel Holtman-Rice, Heinrich H. Buelthoff: Estimation of 3D shape from image orientations. PNAS doi: 10.1073/pnas.1114619109

Long-term music training tunes how the brain temporally binds signals from multiple senses.

Thu, 24 Nov 2011 11:00:00 +0100

Over the years pianists develop a particularly acute sense of the temporal correlation between the movements of the piano keys and the sound of the notes played. However, they are no better than non-musicians at assessing the synchronicity of lip movements and speech. This was discovered by researchers from the Max Planck Institute for Biological Cybernetics in a comparative study on the simultaneous brain processing of stimuli from different senses by musicians and non-musicians. The researchers also used functional magnetic resonance imaging in their study to map the areas of the brain active during this process. According to their findings, in pianists, the perception of asynchronous music and hand movements triggers increased error signals in a circuit involving the cerebellum, premotor and associative areas of the brain, which is refined by piano practicing. The study shows that our sensorimotor experience influences the way in which the brain temporally links signals from different senses during perception.

In a world full of stimuli which affect all senses, the human brain constantly has to link the impressions we perceive in a way that makes sense. We learn through experience, for example, that the synchronous events that arise in a busy bar setting, such as the lip movements of a particular person and the sound of a certain voice, belong together. HweeLing Lee and research group leader Uta Noppeney from the Max Planck Institute for Biological Cybernetics in Tübingen study how the brain integrates stimuli from several senses and how the circuits in the brain change as a result of learning. In their latest study, they examined how well 18 amateur pianists were able to perceive the temporal coincidence between finger movements on the piano keys and a piece of piano music and between lip movements and spoken sentences as compared with 19 non-musicians. “For this study, we availed of the fact that the pianists specifically train in an activity, in which several sensory stimuli, that is visual and auditory information, movement and the striking of the piano keys, have to be connected,” explains Uta Noppeney. During the experiment, the finger or mouth movements were advanced or delayed in relation to the sounds heard at intervals of up to 360 milliseconds. The study participants were requested to specify when asked whether the events were synchronous or asynchronous. Using the same film and sound material and the same participants, the experiments were then repeated using functional magnetic resonance imaging (fMRI). In this case, the subjects remained passive and the machine recorded the areas of the brain that became active during the automatic perception of the synchronous and asynchronous signals. The experiments revealed that the pianists were significantly more accurate than the non-musicians in assessing whether the finger movements on the piano and the sounds heard coincided temporally or not. “The window for the temporal integration of the stimuli in the pianists is clearly narrower than in non-musicians,” says HweeLing Lee. However, the same differences were not observed in the experiments involving spoken sentences and lip movements – both groups recorded similar performances here. In principle, asynchronicity in language and music activates the same areas in the brain. However, the fMRI scans showed that, in the experiment with the pianists, asynchronous music triggered a stronger signal in a circuit involving the left cerebellum, a premotor and associative region in the cerebral cortex than in the non-musicians. “The processing of stimuli in the brains of the pianists points to a context-specific mechanism: as a result of their piano practice, a forward model involving the cerebellum and premotor cerebral cortex is programmed in the circuit which enables the individual to make far more precise predictions about the correct temporal sequence of the visual and auditory signals,” explains Uta Noppeney. “An asynchronous stimulus triggers prediction error signal.” The researchers see this as an important indication of how the brain can generally react in a flexible way to sensorimotor experience. Whether pianists would perform equally well in the assessment of violin music and whether more intensive music playing would influence language processing in the brain remain open questions. “For the next stage in the study of the processing of multiple sensory stimuli in the brain, we will have to train the participants in a specific way so that we can investigate the effects in greater detail,” says Uta Noppeney. Original publication:
HweeLing Lee, Uta Noppeney: Long-term music training tunes how the brain temporally binds signals from multiple senses. PNAS, doi: 10.1073/pnas.1115267108 © Press & Public relations office Max Planck Campus Tuebingen Contact:
Uta Noppeney
E-Mail: uta.noppeney@tuebingen.mpg.de
HweeLing Lee
Tel.: + 49 (0)7071 601- 1786
E-Mail: hwee-ling.lee@tuebingen.mpg.de

Symposium Bayesian Inference: From Spikes to Behaviour

Tue, 25 Oct 2011 00:00:00 +0200

Confirmed speakers: Michael J. Black, Max Planck Institute for Intelligent Systems, Tübingen, Germany
Daniel Braun, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
Opher Donchin, Ben Gurion University of Negev, Be’er Sheva, Israel
Dominik Endres, Eberhard Karls University of Tübingen, Tübingen, Germany
Adrienne Fairhall, University of Washington, Washington, USA
Peter Földiak, University of St. Andrews, St. Andrews, UK
Moritz Grosse-Wentrup, Max Planck Institute for Intelligent Systems, Tübingen, Germany
Konrad Körding, University of Chicago, Illinois, USA
Peter Latham, University College London, London, UK
Jörg Lücke, Frankfurt Institute for Advanced Studies, Goethe Universität Frankfurt, Germany
Laurence Maloney, University of New York, New York, USA
Uta Noppeney, Max Planck Institute for Biological Cybernetics, Tübingen, Germany
Jan Peters, TU Darmstadt, Darmstadt, Germany
Josh Tenenbaum, Massachusetts Institute of Technology, Massachusetts, USA
More information on the program and registration can be found here. Venue:
Casino Schnarrenberg, Conference Center, Otfried-Müller-Str.6, 1st Floor Bernstein symposium series:
The symposium "Multisensory preception and action" is the second in our Bernstein symposium series.

Steffen Katzner is honored with an ERC grant

Tue, 11 Oct 2011 11:33:00 +0200

Steffen Katzner (Werner Reichardt Center for Integrative Neuroscience & BCCN Tübingen) has been awarded a prestigious ERC Starting Grant. The grant provides €1.3 million over five years to support his innovative research. His project was selected by the European Research Council from more than 4000 applications. In total, 16 Starting Grants have been awarded in the state of Baden-Württemberg this year and 480 Europe-wide. Steffen Katzner receives the ERC Starting grant for his research on the neural basis of visual perception. Perceptual processes rely on the coordinated activity of populations of neurons in the cerebral cortex, where they are connected in a highly structured way, forming local cortical circuits. These local circuits are the heart of cortical computation. The goal of Dr. Katzner’s project is to understand cortical circuit function, and to relate activity in cortical circuits to perception and behavior. To achieve this goal, Dr. Katzner focuses on the visual system of the mouse. Owing to increasing availability of molecular biology tools, the mouse is gaining popularity as a model system for basic vision research. Dr. Katzner’s work addresses fundamental principles, which are expected to apply to other sensory modalities and species. Steffen Katzner received his PhD from the University of Göttingen, in collaboration with the German Primate Center. During postdoctoral research, he worked in San Francisco and in London. His group “Neural basis of visual behavior” is part of the Center for Integrative Neuroscience at the University of Tübingen.

What you say is what you see.

Thu, 15 Sep 2011 15:48:00 +0200

How did our lexicon develop? What is the link between the sound of a word and its meaning? Traditionally, scientists claimed that such a link is purely arbitrary and based exclusively on social conventions. New research from the University of Trento, the University of Oxford, and the Max Planck Institute for Biological Cybernetics, however, is now dramatically challenging this view. The findings have now been published in Experimental Brain Research.

“There are natural constraints between the meaning of a word and its sound” claims Cesare Parise of the University of Oxford and the Max Planck Institute, “that is why most people throughout the world would immediately agree that something called mal can’t just be smaller than a mil”.

Cesare Parise and Francesco Pavani set out to examine whether human vocalizations were automatically affected by what they were looking at.

They sat volunteers in front of a computer screen and asked them to vocalize the letter a whenever a figure was shown on the screen. Such figures varied in size, shape, and lightness.

An analysis of volunteers’ vocalizations highlighted a surprising set of regularities: Participants systematically modulated their vocalizations depending on what they were looking at! In particular, participants were louder in response to bright as compared to dark figures, and they were louder in response to spiky rather than rounded figures. Moreover, their vocalizations were sharper for spiky than for rounded figures.

“These results are amazing because volunteers were explicitly instructed to vocalize a meaningless letter in the most natural way, without bothering to worry about what was on the screen” says Parise, “imagine what would happen if they only wished to communicate what they were looking at!”

This research opens new perspectives regarding the development of oral language, and raises the intriguing question of whether there might exist not only a universal grammar common to all languages, but also some universal aspects of the lexicon. That is why, for example, Japanese people can tell, at a greater than chance level, whether a Native American word that they had never heard before is the name of a fish or a bird.

“It has long been known that people tend to pair meaningless heard words with specific visual shapes, as in the famous example in which the word takete is more likely to describe a spiky object than the word maluma.” says Francesco Pavani of the University of Trento, ”The surprising and novel aspect of our research, however, is that even a spontaneous and totally arbitrary vocalization that we utter can change according to the shape we are looking at”.

In the future it might even be possible to use the same technique to investigate whether other animals also automatically modulate their vocalizations in a similar fashion.

The potential applications of these results are manifold. In a clinical setting, the natural mappings between sound and meaning highlighted by Parise and Pavani can be exploited to develop more effective treatments for people with developmental or acquired speech disorders. Moreover, the team believes that knowledge of the right sound for a given concept might be a powerful tool in marketing to find the best fitting name for new products.

Publication:
Parise C & Pavani F (In press) Evidence of sound symbolism in simple vocalizations. Experimental Brain Research.

Contacts:
Cesare Parise: cesare.parise@tuebingen.mpg.de
Francesco Pavani: francesco.pavani@unitn.it