Abstract
Goal. In adults, visual perception changes as a function of polar angle; it is better along the horizontal than vertical meridian, and along the lower than upper vertical meridian. These perceptual asymmetries are linked to similar asymmetries in the cortical magnification of V1, which is greatest along the horizontal and lowest on the upper vertical meridian (Benson et al. 2021, eLife, 10.7554/eLife.67685, Himmelberg et al. 2021, NeuroImage, 10.1016/j.neuroimage.2021.118609). In children, there is a perceptual horizontal-vertical meridian asymmetry, but not a lower-upper vertical meridian asymmetry. Instead, perception is similar along the full vertical meridian. Are these perceptual phenomena in children also linked to cortical magnification? Here, we used fMRI to investigate how cortical magnification changes as a function of polar angle in children, and whether this differs from adults. Methods. In 17 children (ages 5-11), we reanalyzed fMRI data from Gomez et al. (2018, Nature Comms, 10.1038/s41467-018-03166-3). For each V1 map, we quantified the surface area representing the horizontal, upper, and lower vertical meridians by defining ROIs spanning 1-7° eccentricity, and ±15°, ±25°, ±35°, ±45°, or ±55° in polar angle. Results. The cortical magnification asymmetries measured here paralleled the perceptual asymmetries measured previously in another group of children. Within ±25º of the meridians, there was about twice as much V1 surface area representing the horizontal than vertical meridian. However, there was no difference in V1 surface area between the lower and upper vertical meridian. Conclusion. These data show that children have a horizontal-vertical asymmetry in cortical magnification that is similar to adults. However, unlike adults, children show no lower-upper vertical meridian asymmetry in V1 cortical magnification. This suggests that the cortical representation of the vertical meridian changes between childhood to adulthood, synonymous with the emergence of a perceptual vertical meridian asymmetry.