TY - JOUR
T1 - Population receptive field shapes in early visual cortex are nearly circular
AU - Lerma-Usabiaga, Garikoitz
AU - Winawer, Jonathan
AU - Wandell, Brian A.
N1 - Funding Information:
Received Dec. 3, 2020; revised Jan. 3, 2021; accepted Jan. 10, 2021. Author contributions: G.L.-U., J.W., and B.A.W. designed research; G.L.-U., J.W., and B.A.W. performed research; G.L.-U. analyzed data; G.L.-U., J.W., and B.A.W. wrote the paper. This work was supported by the European Union’s Horizon 2020 Research and Innovation Program under the Marie Sklodowska-Curie Grant 795807 (to G.L.-U.) and by National Institutes of Health Grants EY027401, EY027964, and MH111417 (to J.W.). We thank E. Silson, C. Baker, and R. Reynolds. We also thank R. Reynolds for help with the AFNI software. The authors declare no competing financial interests. Correspondence should be addressed to Garikoitz Lerma-Usabiaga at garikoitz@gmail.com. https://doi.org/10.1523/JNEUROSCI.3052-20.2021 Copyright © 2021 the authors
Publisher Copyright:
© 2021 Society for Neuroscience. All rights reserved.
PY - 2021/3/17
Y1 - 2021/3/17
N2 - The visual field region where a stimulus evokes a neural response is called the receptive field (RF). Analytical tools combined with functional MRI (fMRI) can estimate the RF of the population of neurons within a voxel. Circular population RF (pRF) methods accurately specify the central position of the pRF and provide some information about the spatial extent (diameter) of the RF. A number of investigators developed methods to further estimate the shape of the pRF, for example, whether the shape is more circular or elliptical. There is a report that there are many pRFs with highly elliptical pRFs in early visual cortex (V1-V3; Silson et al., 2018). Large aspect ratios (>2) are difficult to reconcile with the spatial scale of orientation columns or visual field map properties in early visual cortex. We started to replicate the experiments and found that the software used in the publication does not accurately estimate RF shape: it produces elliptical fits to circular ground-truth data. We analyzed an independent data set with a different software package that was validated over a specific range of measurement conditions, to show that in early visual cortex the aspect ratios are <2. Furthermore, current empirical and theoretical methods do not have enough precision to discriminate ellipses with aspect ratios of 1.5 from circles. Through simulation we identify methods for improving sensitivity that may estimate ellipses with smaller aspect ratios. The results we present are quantitatively consistent with prior assessments using other methodologies.
SIGNIFICANCE STATEMENT We evaluated whether the shape of many population receptive fields (RFs) in early visual cortex is elliptical and differs substantially from circular. We evaluated two tools for estimating elliptical models of the pRF; one tool was valid over the measured compliance range. Using the validated tool, we found no evidence that confidently rejects circular fits to the pRF in visual field maps V1, V2, and V3. The new measurements and analyses are consistent with prior theoretical and experimental assessments in the literature.
AB - The visual field region where a stimulus evokes a neural response is called the receptive field (RF). Analytical tools combined with functional MRI (fMRI) can estimate the RF of the population of neurons within a voxel. Circular population RF (pRF) methods accurately specify the central position of the pRF and provide some information about the spatial extent (diameter) of the RF. A number of investigators developed methods to further estimate the shape of the pRF, for example, whether the shape is more circular or elliptical. There is a report that there are many pRFs with highly elliptical pRFs in early visual cortex (V1-V3; Silson et al., 2018). Large aspect ratios (>2) are difficult to reconcile with the spatial scale of orientation columns or visual field map properties in early visual cortex. We started to replicate the experiments and found that the software used in the publication does not accurately estimate RF shape: it produces elliptical fits to circular ground-truth data. We analyzed an independent data set with a different software package that was validated over a specific range of measurement conditions, to show that in early visual cortex the aspect ratios are <2. Furthermore, current empirical and theoretical methods do not have enough precision to discriminate ellipses with aspect ratios of 1.5 from circles. Through simulation we identify methods for improving sensitivity that may estimate ellipses with smaller aspect ratios. The results we present are quantitatively consistent with prior assessments using other methodologies.
SIGNIFICANCE STATEMENT We evaluated whether the shape of many population receptive fields (RFs) in early visual cortex is elliptical and differs substantially from circular. We evaluated two tools for estimating elliptical models of the pRF; one tool was valid over the measured compliance range. Using the validated tool, we found no evidence that confidently rejects circular fits to the pRF in visual field maps V1, V2, and V3. The new measurements and analyses are consistent with prior theoretical and experimental assessments in the literature.
KW - Fmri
KW - Population receptive field
KW - Visual cortex
KW - Visual Cortex/physiology
KW - Algorithms
KW - Brain Mapping/methods
KW - Computer Simulation
KW - Humans
KW - Software
KW - Models, Neurological
UR - http://www.scopus.com/inward/record.url?scp=85103117812&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85103117812&partnerID=8YFLogxK
U2 - 10.1523/JNEUROSCI.3052-20.2021
DO - 10.1523/JNEUROSCI.3052-20.2021
M3 - Article
C2 - 33531414
AN - SCOPUS:85103117812
SN - 0270-6474
VL - 41
SP - 2420
EP - 2427
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 11
ER -