Research interests
Sensory information received by the brain is typically uncertain (for instance because of poor signal quality or ambiguity in the world), yet it must constantly be manipulated to generate accurate, task-relevant behavior. In our laboratory, we investigate how the brain represents and processes uncertain information. This is critical for approaching a key problem in systems neuroscience, that of understanding the relationship between perceptual behavior and neural activity.
There is good evidence from human studies that the brain weighs and integrates pieces of information in a way that takes into account their uncertainty. (In the jargon of the field, this is called "Bayes-optimal" performance.) We study such behaviors using computational modeling and psychophysics in a variety of domains, including multisensory perception, decision-making, and visual search. We are particularly interested in pushing the boundaries of Bayesian optimality by considering complex stimuli (like auditory-visual speech), complex computations (like those involved in visual search), and patient populations.
At the neural level, the idea has gained ground that neural populations maintain representations of uncertainty (or even of entire probability distributions) and use these to perform optimal computation. We use theories of neural coding and large-scale simulations of biologically realistic neural networks to study how optimal computations can be implemented in the brain. For example, we have shown that optimal cue integration can be achieved through relatively simple neural operations, provided that trial-to-trial neural variability is of a certain form. This general approach has the potential to make physiologically testable predictions in many areas of cognition.
Publications
(Underlined: joint first authors)
- Ma WJ, Pouget A (2008). Linking neurons to behavior in multisensory perception: a computational review. Brain Research Reviews, in press.
- Ma WJ, Pouget A (2008). Population coding. In New Encyclopedia of Neuroscience. Squire LR (ed.), Elsevier Ltd, in press.
- Beierholm U, Kording K, Shams L, Ma WJ (2007), Comparing Bayesian models for multisensory cue combination without mandatory integration. Advances in Neural Information Processing Systems.
- Ma WJ, Beck JM, Latham PE, Pouget A (2006), Bayesian inference with probabilistic population codes. Nature Neuroscience 9 (11), 1432-8.
- Kording K, Beierholm U, Ma WJ, Quartz S, Tenenbaum JB, Shams L (2007). Causal inference in multisensory perception. PLoS ONE 2, e943.
- Beck JM, Ma WJ, Latham PE, Pouget A (2007), Probabilistic population codes and the exponential family of distributions. In Progress in Brain Research Vol. 165. Cisek, Drew, and Kalaska (eds.), 511-521, Elsevier Ltd.
- Ma WJ, Hamker F, Koch C (2006). Neural Mechanisms Underlying Temporal Aspects of Conscious Visual Perception.
in The First Half Second: The Microgenesis and Temporal Dynamics of Unconscious and Conscious Visual Processes,Ögmen H, Breitmeyer BG eds., 275-94, MIT Press.
- Shams L, Ma WJ, Beierholm U (2005). Sound-induced flash illusion as an optimal percept. NeuroReport 16 (17), 1923-7.
- Wilken P, Ma WJ (2004).
A detection theory account of change detection. Journal of Vision 4 (12), 1120-35.
- Hofman C, Ma WK, Deformations of closed strings and topological open membranes. Journal of High Energy Physics 06 (2001) 033.
- Hofman C, Ma WK, Deformations of topological open strings. Journal of High Energy Physics 01 (2001) 035.
Education
- Postdoctoral scholar, lab of Alex Pouget, Department of Brain and Cognitive Sciences, University of Rochester, 2004-present
- Postdoctoral scholar, lab of Christof Koch, Department of Biology, California Institute of Technology, 2002-4
- Ph.D. in Theoretical Physics, University of Groningen, the Netherlands, 2001
- M.Sc. in Mathematics, University of Groningen, the Netherlands, 1997
- M.Sc. in Theoretical Physics, University of Groningen, the Netherlands, 1996
Teaching and outreach
- Invited lecturer in "Normative Theories of Brain Function", CF Neuroscience Programme at the Instituto Gulbenkian de Ciência.
- Volunteer teaching assistant for Classical Mechanics and Special Relativity. California Institute of Technology, 2004-5.
- Designed curriculum and taught with the Rural China Education Foundation in middle schools in rural China. 2004-6
- Founder and coordinator of Physics Promotion Team (outreach to Dutch high schools). University of Groningen, 2002.
- Teaching assistant for Mathematical Methods of Physics, Classical Mechanics, and Quantum Physics. University of Groningen, 1997-9
Collaborators
(Past and present)
Links to some other labs
