Topographic representations of object size and relationships with numerosity reveal generalized quantity processing in human parietal cortex

Harvey, B.M., Fracasso, A. , Petridou, N. and Dumoulin, S.O. (2015) Topographic representations of object size and relationships with numerosity reveal generalized quantity processing in human parietal cortex. Proceedings of the National Academy of Sciences of the United States of America, 112(44), pp. 13525-13530. (doi:10.1073/pnas.1515414112) (PMID:26483452) (PMCID:PMC4640722)

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Abstract

Humans and many animals analyze sensory information to estimate quantities that guide behavior and decisions. These quantities include numerosity (object number) and object size. Having recently demonstrated topographic maps of numerosity, we ask whether the brain also contains maps of object size. Using ultra-high-field (7T) functional MRI and population receptive field modeling, we describe tuned responses to visual object size in bilateral human posterior parietal cortex. Tuning follows linear Gaussian functions and shows surround suppression, and tuning width narrows with increasing preferred object size. Object size-tuned responses are organized in bilateral topographic maps, with similar cortical extents responding to large and small objects. These properties of object size tuning and map organization all differ from the numerosity representation, suggesting that object size and numerosity tuning result from distinct mechanisms. However, their maps largely overlap and object size preferences correlate with numerosity preferences, suggesting associated representations of these two quantities. Object size preferences here show no discernable relation to visual position preferences found in visuospatial receptive fields. As such, object size maps (much like numerosity maps) do not reflect sensory organ structure but instead emerge within the brain. We speculate that, as in sensory processing, optimization of cognitive processing using topographic maps may be a common organizing principle in association cortex. Interactions between object size and numerosity maps may associate cognitive representations of these related features, potentially allowing consideration of both quantities together when making decisions.

Item Type:Articles
Additional Information:This work was supported by Netherlands Organization for Scientific Research Grants 452.08.008 (to S.O.D.) and 433.09.223 (to S.O.D. and F. W. Cornelissen) and by Portuguese Foundation for Science and Technology Grant IF/01405/2014 (to B.M.H.).
Keywords:Association cortex, brain mapping, cognition, controlled study, decision making, functional magnetic resonance imaging, human, human experiment, left hemisphere, posterior parietal cortex, quantitative analysis, right hemisphere, sensory stimulation, topography, visual field, adult, anatomy and histology, computer simulation, male, nuclear magnetic resonance imaging, parietal lobe, pattern recognition, perception, photostimulation, physiology, procedures, randomization, theoretical model, adult, brain mapping, computer simulation, form perception, humans, magnetic resonance imaging, male, models, theoretical, parietal lobe, pattern recognition, visual, photic stimulation, random allocation, size perception.
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Fracasso, Dr Alessio
Authors: Harvey, B.M., Fracasso, A., Petridou, N., and Dumoulin, S.O.
College/School:College of Medical Veterinary and Life Sciences > Institute of Neuroscience and Psychology
Journal Name:Proceedings of the National Academy of Sciences of the United States of America
Publisher:National Academy of Sciences
ISSN:0027-8424
ISSN (Online):1091-6490
Published Online:19 October 2015

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