Biology subjects

DeYoe, E. A.

Publications and source records attributed to DeYoe, E. A..

3 recordsLinked to original sources

bioRxiv2024

BOLD Contrast Response Characteristics of Aberrant Voxels with Bilateral Visual Population Receptive Fields in Human Albinism

Albinism is an inherited disorder characterized by disrupted melanin production in the eye, and often in the skin and hair. This retinal hypopigmentation is accompanied by pathological decussation of many temporal retinal afferents at the optic chiasm during development, ultimately resulting in partially superimposed representations of opposite visual hemifields in each cortical hemisphere. Within these aberrant regions of hemifield overlap, individual voxels have been shown to have bilateral, dual population receptive fields (pRFs) responding to roughly mirror-image locations across the vertical meridian. Nonetheless, how these two conflicting inputs combine to determine a voxels response to image contrast is still unknown. To address this, we stimulated the right and left hemifields with separately controlled sinusoidal gratings, each having a variety of contrasts (0, 8, 20, 45, 100%), and extracted voxel-wise BOLD response amplitudes to each contrast combination in visual areas V1-V3. We then compared voxels responses to each hemifield stimulated individually with conditions when both hemifields were stimulated simultaneously. We hypothesized that simultaneous stimulation of the two pRF components will result in either a suppressive or facilitative interaction. However, we found that BOLD responses to simultaneous stimulation appeared to reflect simple summation of the neural activity from the individual hemifield conditions. This suggests that the superimposed opposite hemifield representations do not interact. Thus, dual pRFs in albinism likely reflect two co-localized, but functionally independent populations of neurons each of which respond to a single hemifield. This finding is commensurate with psychophysical studies which have shown no clear perceptual interaction between opposite visual hemifields in human albinism.

neuroscience↗

bioRxiv2019

Aberrant Population Receptive Fields in Human Albinism

Retinotopic organization is a fundamental feature of visual cortex thought to play a vital role in encoding spatial information. One important aspect of normal retinotopy is the representation of the right and left hemifields in contralateral visual cortex. However, in human albinism, many temporal retinal afferents decussate pathologically at the optic chiasm resulting in partially superimposed representations of opposite hemifields in each hemisphere of visual cortex. Previous fMRI studies in human albinism suggest that the right and left hemifield representations are superimposed in a mirror-symmetric manner. This should produce imaging voxels which respond to two separate regions in visual space mirrored across the vertical meridian. However, it is not yet clear how retino-cortical miswiring in albinism manifests at the level of single voxel population receptive fields. Here we used fMRI retinotopic mapping in conjunction with population receptive field (pRF) modeling to fit both single and dual pRF models to the visual responses of voxels in visual areas V1-V3 of five subjects with albinism. We found that subjects with albinism (but not controls) have sizable clusters of voxels with dual pRFs consistently corresponding to, but not fully coextensive with regions of hemifield overlap. These dual pRFs were typically positioned at roughly mirror image locations across the vertical meridian but were uniquely clustered within the visual field for each subject. We also found that single pRFs are larger in albinism than controls, and that single pRF sizes in the central visual field were anti-correlated with subjects foveal cone densities. Finally, dual pRF and aberrant hemifield representation characteristics varied significantly across subjects with albinism suggesting more central heterogeneity than previously appreciated.

neuroscience↗

bioRxiv2019

Retinal and Cortical Determinants of Cortical Magnification in Human Albinism

The human fovea lies at the center of the retina and supports high-acuity vision. In normal visual system development, foveal acuity is correlated with both a high density of cone photoreceptors at this location and a magnified retinotopic representation of the fovea in the visual cortex. Both cone density and the cortical area dedicated to each degree of visual space--the latter known as the cortical magnification function--steadily decline with increasing eccentricity from the fovea. In albinism, peak cone density at the fovea and visual acuity are reduced but appear to be normal in the periphery, thus providing a model to explore the correlation between retinal structure, cortical structure, and behavior. Here, we used adaptive optics scanning light ophthalmoscopy to assess retinal cone density and functional magnetic resonance imaging to measure cortical magnification in primary visual cortex of normal controls and individuals with albinism. We find that retinotopic organization is more varied in albinism than previously appreciated, yet cortical magnification outside the fovea is similar to that in controls. Moreover, cortical magnification in albinism and controls exceeds that which might be predicted based on cone density alone, suggesting that reduced foveal cone density in the albinotic retina may be partially counteracted by central connectivity. Together, these results emphasize that central as well as retinal factors must be included to provide a complete picture of aberrant structure and function in genetic conditions such as albinism.

neuroscience↗