Imaging surround modulation in human visual cortex

Simo Vanni (Aalto University)
Host Institution: 
Lomonosov' Moscow State University

Welcome on the next seminar of BioN programme on Thur 23.06.2011 at 17.00 in Aud 462 of Dep. Higher Nervous System of Biological Facylty of Lomonosov' MSU

Imaging surround modulation in human visual cortex

Simo Vanni, MD PhD, Brain Research Unit & AMI Centre, Low Temperature Laboratory, Aalto University School of Science, Espoo, Finland

Cortical response to a visual stimulus can be modulated by other stimuli presented elsewhere in the visual field. Multidisciplinary research efforts have found such contextual modulation ubiquitously in sensory systems and these findings have redefined the concept of receptive field. We have explored contextual modulation between visual stimuli with brain imaging, and found that when stimuli are far from each other, interaction emerges first in the extrastriate (non-primary) cortices, followed by a spread to the whole system. In the primary visual cortex, psychophysical data correctly predicted functional magnetic resonance imaging (fMRI) area tuning response, but required a model to account for the large number of cells within one fMRI volumetric unit. Recently we quantified the spread of fMRI signal for visual stimuli, and found  large spread of signal already in the primary visual cortex. Spread of fMRI signal indicates spread of population response, particularly synaptic activity. Thus, such large spread outside the primary retinotopic representation may be able to account for the modulatory "extra-classical" receptive field where stimulation can modify single neuron response, without being able to drive neurons without stimulation simultaneously in the centre of the receptive field. These and other earlier robust regularities in contextual modulation across functional areas may reflect principles of efficient coding. Visual system provides a good laboratory for studying these principles in human cerebral cortex. 

Simo Vanni, MD from University of Helsinki 1990

PhD from Helsinki University of Technology and University of Helsinki 1998 

Marie Curie individual fellow working with Jean Bullier 2000-2002 at Centre de Recherche Cerveau & Cognition, Toulouse, France

Docent (senior lecturer) of Neurophysiology, 2006, University of Helsinki

Currently Academy research fellow leading a group specialized in vision systems physiology at Brain Research Unit, Low Temperature Laboratory, Aalto university School of science, Espoo, Finland

 and Scientific director of the Advanced Magnetic Imaging Centre at Aalto University 

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