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Neural population tuning links visual cortical anatomy to human visual perception.

Song C, Schwarzkopf DS, Kanai R, Rees G - Neuron (2015)

Bottom Line: We found that visual cortical thickness correlated negatively with the sharpness of neural population tuning and the accuracy of perceptual discrimination at different visual field positions.In contrast, visual cortical surface area correlated positively with neural population tuning sharpness and perceptual discrimination accuracy.Our findings reveal a central role for neural population tuning in linking visual cortical anatomy to visual perception and suggest that a perceptually advantageous visual cortex is a thinned one with an enlarged surface area.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AR, UK; Wellcome Trust Centre for Neuroimaging, University College London, 12 Queen Square, London WC1N 3BG, UK. Electronic address: chen.song.09@ucl.ac.uk.

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Variability in Visual Cortical Surface AreaVariability in visual cortical surface area was studied in a group of 20 participants, where we applied the standard method of retinotopic mapping to delineate the part of early visual cortices (V1 and V2) that responded to the visual field between 0.25 and 7.2 degree eccentricity. Based on the retinotopy delineation, visual cortical surface area was calculated as the surface area summed over all cortical locations in the retinotopically delineated part of V1 or V2. This retinotopically delineated visual cortical surface area exhibited a 2-fold interindividual variability (illustrated in the marginal histogram of A) that was correlated between V1 and V2 (illustrated in the scatter plot of A). To quantify the fraction of retinotopically delineated V1 or V2 to full V1 or V2, the distribution of mapped visual field eccentricity was plotted on a voxel basis, where voxels responsive to similar eccentricity were binned to generate 30 data points for each participant (B). From the exponential fit to the eccentricity distribution, we estimated the retinotopically delineated V1 or V2 as the area under the exponential fit between x equaled 0.25 and x equaled 7.2, and the full V1 or V2 as the area under the exponential fit between x equaled 0 and x approximated infinite. Data points are color coded according to the participant (B). Parameters reflect the fraction of retinotopically delineated V1 or V2 (B).
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fig1: Variability in Visual Cortical Surface AreaVariability in visual cortical surface area was studied in a group of 20 participants, where we applied the standard method of retinotopic mapping to delineate the part of early visual cortices (V1 and V2) that responded to the visual field between 0.25 and 7.2 degree eccentricity. Based on the retinotopy delineation, visual cortical surface area was calculated as the surface area summed over all cortical locations in the retinotopically delineated part of V1 or V2. This retinotopically delineated visual cortical surface area exhibited a 2-fold interindividual variability (illustrated in the marginal histogram of A) that was correlated between V1 and V2 (illustrated in the scatter plot of A). To quantify the fraction of retinotopically delineated V1 or V2 to full V1 or V2, the distribution of mapped visual field eccentricity was plotted on a voxel basis, where voxels responsive to similar eccentricity were binned to generate 30 data points for each participant (B). From the exponential fit to the eccentricity distribution, we estimated the retinotopically delineated V1 or V2 as the area under the exponential fit between x equaled 0.25 and x equaled 7.2, and the full V1 or V2 as the area under the exponential fit between x equaled 0 and x approximated infinite. Data points are color coded according to the participant (B). Parameters reflect the fraction of retinotopically delineated V1 or V2 (B).

Mentions: From our MRI-based measure of visual cortical anatomy, we studied variability in visual cortical surface area and visual cortical thickness. Consistent with previous reports (Dougherty et al., 2003), the retinotopically delineated visual cortical surface area exhibited a 2-fold interindividual variability (Figure 1A, summed across left and right hemispheres; V1, 2,213 mm2 to 3,328 mm2 and V2, 1,611 mm2 to 2,936 mm2) that was correlated between V1 and V2 (Figure 1A; r = 0.568, p < 0.05, n = 20). As the retinotopy delineation covered a part rather than the full extent of early visual cortices, we further explored interindividual variability in the fraction of retinotopy coverage, based on the distribution of mapped visual field eccentricity derived from the eccentricity map. This distribution was best fitted with an exponential function y = ae−bx, which reflected the percentage of voxels responsive to each visual field eccentricity (Figure 1B). Given that different voxels were equal in volume, we estimated the retinotopically delineated part of early visual cortices as the area under the exponential curve from x equaled 0.25 degree eccentricity to x equaled 7.2 degree eccentricity, and the full extent of early visual cortices as the area under the exponential curve from x equaled 0 to x approximated infinite. We found that in both V1 and V2, the retinotopically delineated part accounted for about three-quarters of the full area. This fraction of retinotopy coverage was rather consistent across participants (V1, mean = 78.3%, SD = 3.7%, n = 20 and V2, mean = 78.8%, SD = 3.3%, n = 20) and did not correlate with the measure of visual cortical surface area (V1, r = −0.120, p = 0.564, n = 20 and V2, r = 0.080, p = 0.768, n = 20). Therefore, we concluded that the retinotopically delineated visual cortical surface area captured true anatomical variability.


Neural population tuning links visual cortical anatomy to human visual perception.

Song C, Schwarzkopf DS, Kanai R, Rees G - Neuron (2015)

Variability in Visual Cortical Surface AreaVariability in visual cortical surface area was studied in a group of 20 participants, where we applied the standard method of retinotopic mapping to delineate the part of early visual cortices (V1 and V2) that responded to the visual field between 0.25 and 7.2 degree eccentricity. Based on the retinotopy delineation, visual cortical surface area was calculated as the surface area summed over all cortical locations in the retinotopically delineated part of V1 or V2. This retinotopically delineated visual cortical surface area exhibited a 2-fold interindividual variability (illustrated in the marginal histogram of A) that was correlated between V1 and V2 (illustrated in the scatter plot of A). To quantify the fraction of retinotopically delineated V1 or V2 to full V1 or V2, the distribution of mapped visual field eccentricity was plotted on a voxel basis, where voxels responsive to similar eccentricity were binned to generate 30 data points for each participant (B). From the exponential fit to the eccentricity distribution, we estimated the retinotopically delineated V1 or V2 as the area under the exponential fit between x equaled 0.25 and x equaled 7.2, and the full V1 or V2 as the area under the exponential fit between x equaled 0 and x approximated infinite. Data points are color coded according to the participant (B). Parameters reflect the fraction of retinotopically delineated V1 or V2 (B).
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fig1: Variability in Visual Cortical Surface AreaVariability in visual cortical surface area was studied in a group of 20 participants, where we applied the standard method of retinotopic mapping to delineate the part of early visual cortices (V1 and V2) that responded to the visual field between 0.25 and 7.2 degree eccentricity. Based on the retinotopy delineation, visual cortical surface area was calculated as the surface area summed over all cortical locations in the retinotopically delineated part of V1 or V2. This retinotopically delineated visual cortical surface area exhibited a 2-fold interindividual variability (illustrated in the marginal histogram of A) that was correlated between V1 and V2 (illustrated in the scatter plot of A). To quantify the fraction of retinotopically delineated V1 or V2 to full V1 or V2, the distribution of mapped visual field eccentricity was plotted on a voxel basis, where voxels responsive to similar eccentricity were binned to generate 30 data points for each participant (B). From the exponential fit to the eccentricity distribution, we estimated the retinotopically delineated V1 or V2 as the area under the exponential fit between x equaled 0.25 and x equaled 7.2, and the full V1 or V2 as the area under the exponential fit between x equaled 0 and x approximated infinite. Data points are color coded according to the participant (B). Parameters reflect the fraction of retinotopically delineated V1 or V2 (B).
Mentions: From our MRI-based measure of visual cortical anatomy, we studied variability in visual cortical surface area and visual cortical thickness. Consistent with previous reports (Dougherty et al., 2003), the retinotopically delineated visual cortical surface area exhibited a 2-fold interindividual variability (Figure 1A, summed across left and right hemispheres; V1, 2,213 mm2 to 3,328 mm2 and V2, 1,611 mm2 to 2,936 mm2) that was correlated between V1 and V2 (Figure 1A; r = 0.568, p < 0.05, n = 20). As the retinotopy delineation covered a part rather than the full extent of early visual cortices, we further explored interindividual variability in the fraction of retinotopy coverage, based on the distribution of mapped visual field eccentricity derived from the eccentricity map. This distribution was best fitted with an exponential function y = ae−bx, which reflected the percentage of voxels responsive to each visual field eccentricity (Figure 1B). Given that different voxels were equal in volume, we estimated the retinotopically delineated part of early visual cortices as the area under the exponential curve from x equaled 0.25 degree eccentricity to x equaled 7.2 degree eccentricity, and the full extent of early visual cortices as the area under the exponential curve from x equaled 0 to x approximated infinite. We found that in both V1 and V2, the retinotopically delineated part accounted for about three-quarters of the full area. This fraction of retinotopy coverage was rather consistent across participants (V1, mean = 78.3%, SD = 3.7%, n = 20 and V2, mean = 78.8%, SD = 3.3%, n = 20) and did not correlate with the measure of visual cortical surface area (V1, r = −0.120, p = 0.564, n = 20 and V2, r = 0.080, p = 0.768, n = 20). Therefore, we concluded that the retinotopically delineated visual cortical surface area captured true anatomical variability.

Bottom Line: We found that visual cortical thickness correlated negatively with the sharpness of neural population tuning and the accuracy of perceptual discrimination at different visual field positions.In contrast, visual cortical surface area correlated positively with neural population tuning sharpness and perceptual discrimination accuracy.Our findings reveal a central role for neural population tuning in linking visual cortical anatomy to visual perception and suggest that a perceptually advantageous visual cortex is a thinned one with an enlarged surface area.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cognitive Neuroscience, University College London, 17 Queen Square, London WC1N 3AR, UK; Wellcome Trust Centre for Neuroimaging, University College London, 12 Queen Square, London WC1N 3BG, UK. Electronic address: chen.song.09@ucl.ac.uk.

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