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This Article Full Text Full Text (PDF) Supplemental Material All Versions of this Article: 102/5/2900    most recent 00201.2009v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Nurminen, L. Articles by Vanni, S. PubMed PubMed Citation Articles by Nurminen, L. Articles by Vanni, S.

RESEARCH-ARTICLE

Area Summation in Human Visual System: Psychophysics, fMRI, and Modeling

Lauri Nurminen^1,2, Markku Kilpeläinen², Pentti Laurinen^2, and Simo Vanni¹

¹Brain Research Unit, Low Temperature Laboratory, and Advanced Magnetic Imaging Centre, Helsinki University of Technology, Espoo; and ²Department of Psychology, University of Helsinki, Helsinki, Finland

Submitted 10 March 2009; accepted in final form 23 August 2009

ABSTRACT

Contextual modulation is a fundamental feature of sensory processing, both on perceptual and on single-neuron level. When the diameter of a visual stimulus is increased, the firing rate of a cell typically first increases (summation field) and then decreases (surround field). Such an area summation function draws a comprehensive profile of the receptive field structure of a neuron, including areas outside the classical receptive field. We investigated area summation in human vision with psychophysics and functional magnetic resonance imaging (fMRI). The stimuli were similar to those used drifting sine wave gratings in previous macaque single-cell area summation studies. A model was developed to facilitate comparison of area summation in fMRI to area summation in psychophysics and single cells. The model consisted of units with an antagonistic receptive field structure found in single cells in the primary visual cortex. The receptive field centers of the model neurons were distributed in the region of the visual field covered by a single voxel. The measured area summation functions were qualitatively similar to earlier single-cell data. The model with parameters derived from psychophysics captured the spatial structure of the summation field in the primary visual cortex as measured with fMRI. The model also generalized to a novel situation in which the neural population was displaced from the stimulus center. The current study shows that contextual modulation arises from similar spatially antagonistic and overlapping excitatory and inhibitory mechanisms, both in single cells and in human vision.