Fig 1.
Examples of retinotopic maps and schematic of V1 parcellation into visual field segments.
(A) Examples of polar angle and eccentricity maps projected onto the inflated right hemisphere for 4 observers. The ‘Observer 40’ mesh is zoomed in to show V1, the outline of which is illustrated by the black border. (B) Schematic of the parcellation of the V1 representation into eccentricity and polar angle segments for a single hemisphere. For each observer, and each hemisphere, V1 is parcellated into 64 segments (eight 22.5°-polar-angle segments and eight 1°-eccentricity segments) using the retinotopy data.
Fig 2.
Examples of (A) pinwheel and (B) annulus stimuli used for estimating V1 spatial frequency tuning curves.
These are three of the 10 spatial scales tested (base frequencies of 3, 8, and 35). The local spatial frequency of each stimulus increases with distance from the center. For the top and bottom rows, the local spatial frequency is matched at corresponding locations, but the orientations are orthogonal.
Fig 3.
Computing cortical magnification and spatial frequency tuning curves from V1 segments.
(A) Schematic of the left visual hemifield broken down into 64 V1 segments (eight 22.5° polar angle wedges, eight 1° eccentricity segments). Data in (B) and (C) are derived from vertices spatially tuned to the example locations in (A). (B) Group-average log-Gaussian fits for example V1 segments. In the examples shown, a log-Gaussian is fit to combined stimuli data (i.e., BOLD responses averaged between pinwheel and annuli stimuli). The dashed colored lines in the third plot show the preferred spatial frequency (cpd) for two example segments. Error bars represent ±1 standard deviation (SD) across 50 bootstrapped group-averages. (C) To compute cortical magnification (mm/deg): the surface area of the vertices within each V1 segment (shown by the colored square in the right hemisphere V1 schematic) are summed and then divided by the amount of visual space that the segment encodes, shown by the corresponding visual field segment in (A). We then take the square root of this value to compute linear cortical magnification.
Fig 4.
Visualization of 2D model predicting how neural properties vary throughout the V1 representation.
(A) The decline in a neural property (in this case, V1 preferred spatial frequency or cortical magnification) as a function of eccentricity is described by the widely adopted parameterization from [7]. (B) V1 neural properties can be modulated by polar angle; the model predicts larger values along the horizontal (0°, 180°) than vertical meridian (90°, 270°), and along the lower vertical (270°) than upper vertical (90°) meridian of the visual field. (C) Visualization of the full model showing how a neural property varies throughout the visual field; the decline in preferred spatial frequency or cortical magnification from (A) is modulated by a function of polar angle from (B).
Fig 5.
Preferred spatial frequency and cortical magnification throughout the visual field.
Each data point comes from a V1 segment, and each color corresponds to an eccentricity bin. The model fit is shown as lines for each eccentricity bin, although only a single model was fit to the full range of data in each of (A) preferred spatial frequency and (B) cortical magnification.
Table 1.
Median model parameter estimates and 95% confidence intervals from the models fit to measurements of preferred spatial frequency and cortical magnification.
Fig 6.
HVA and VMA indices for preferred spatial frequency and cortical magnification.
(A) Mean HVA indices; the colored plots show the HVA index for preferred spatial frequency and cortical magnification from the current study (n = 40). The gray plots show the HVA index for cortical magnification derived from previous reports; Benson et al. (2021) [14]: 1–6° eccentricity, 20° angle, n = 163; Himmelberg, Kurzawski et al. (2021) [33]: 1-8° eccentricity, 25° angle, n = 44; Himmelberg et al (2022) [20]: 1–8° eccentricity, 15° angle, n = 29; Himmelberg et al. (2023) [32]: 1–7° eccentricity, 25° angle, n = 24. (B) is the same as (A) but VMA indices. Current study error bars show ±1 SD across bootstraps across participants, and prior study error bars show ±1 standard error of the mean (SEM) across participants.
Fig 7.
Covariation between V1 preferred spatial frequency and cortical magnification when measured as a function of eccentricity and polar angle.
Measurements of (A) preferred spatial frequency and (B) cortical magnification (CM) vary as a function of eccentricity (summarized over polar angle). The colored data points represent group-average measurements and the black line represents the 2D models (summarized over polar angle) fit to the data. (C) Covariation between preferred spatial frequency and CM as a function of eccentricity; the colored data points come from (A) and (B). The line of proportionality (y = mx) is shown as the black dashed linear fit through the data and an ordinary least products (OLP) regression line (y = mx + b) is shown in green. (D-F) The same as above, but the preferred spatial frequency and CM measurements –and model fits– vary as a function of polar angle (summarized over eccentricity). Error bars represent ±1 SD cross 50 bootstrapped group-averages.
Fig 8.
Covariation between overall V1 preferred spatial frequency and overall V1 cortical magnification as a function of individual observer.
Each gray data point represents an individual (n = 40). The line of proportionality (y = mx) is shown as the black dashed linear fit through the data and an ordinary least products (OLP) regression line (y = mx + b) is shown in green.
Fig 9.
Calculations of retinal ganglion cell (RGC) per spatial frequency cycle and per mm of V1 cortex.
(A) Measurements of RGCs per cycle of stimulus spatial frequency at preferred spatial frequency as a function of eccentricity, for the 3 meridians and the average of V1. (B) The same as (A) but for RGCs per mm of V1 surface area. (C) Measurements of degrees of visual space per cycle of stimulus spatial frequency at preferred spatial frequency as a function of eccentricity. (D) The same as (C) but for degrees of visual space per mm of V1 surface area.