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Updated: Nov 19, 2025
06:02
Topographical Estimation of Visual Population Receptive Fields by fMRI
Published on: February 3, 2015
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Population Receptive Field Shapes in Early Visual Cortex Are Nearly Circular
Garikoitz Lerma-Usabiaga1,2,3, Jonathan Winawer4, Brian A Wandell5,2
1Department of Psychology, Stanford University, Stanford, California 94305 garikoitz@gmail.com.
Summary
Receptive fields (RFs) in the early visual cortex are not significantly elliptical. Analysis of visual cortex data using validated software shows RFs are closer to circular, contradicting previous claims of high ellipticity.
Area of Science:
- Neuroscience
- Visual Perception
- Computational Neuroscience
Background:
- The population receptive field (pRF) describes the visual field area eliciting a neural response within a voxel.
- Previous studies suggested highly elliptical pRFs in early visual cortex (V1-V3), challenging existing models.
- Estimating pRF shape is crucial for understanding visual processing.
Purpose of the Study:
- To rigorously evaluate the shape of population receptive fields (pRFs) in the early visual cortex (V1-V3).
- To assess the accuracy of software tools used for estimating pRF shape, particularly ellipticity.
- To determine if pRFs in early visual cortex are predominantly circular or elliptical.
Main Methods:
- Replicated previous experiments using population receptive field (pRF) modeling with functional MRI (fMRI) data.
- Evaluated two software packages for pRF shape estimation, including one validated for accuracy.
- Analyzed an independent dataset using the validated software to assess pRF aspect ratios in V1-V3.
Main Results:
- One software package inaccurately estimated pRF shape, fitting ellipses to circular data.
- Analysis with a validated software package revealed pRF aspect ratios <2 in early visual cortex.
- Current methods lack the precision to reliably distinguish between aspect ratios of 1.5 and circular pRFs.
Conclusions:
- There is no confident evidence to reject circular fits for pRFs in visual areas V1, V2, and V3.
- The findings contradict prior reports of highly elliptical pRFs in early visual cortex.
- Results align with existing theoretical and experimental assessments, supporting predominantly circular pRFs.
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