Biology subjects

Jenks, S. K.

Publications and source records attributed to Jenks, S. K..

3 recordsLinked to original sources

bioRxiv2025

Subfoveal scotomas trigger fine-scale fixation reorganization: insights from retinal imaging and retinal-contingent stimulation

Fine spatial vision relies on the foveola, the 1-degree retinal region with highest cone density. Despite its importance, the relationship between retinal anatomy, fixational behavior, and visual perception in the foveola is not fully understood. Using an Adaptive Optics Scanning Light Ophthalmoscope for high-resolution retinal imaging and stimulation, we studied the effect of a simulated subfoveolar ({approx}0.03 degrees2) scotoma on fine spatial vision and fixation behavior in healthy observers. Our findings show that the visuomotor system adapts to the scotoma with striking precision by shifting the preferred locus of fixation in a systematic fashion by minute ({approx}5 arcmin) amounts to bring stimuli into a region of visibility. These results reveal an unprecedented level of fine-scale plasticity in the human visuomotor system. Interestingly, this new retinal locus of fixation is characterized by lower cone density among those surrounding the scotoma, indicating that factors beyond spatial sampling maximization influence these fine-scale adjustments.

neuroscience↗

bioRxiv2024

Asymmetries in foveal vision

Visual perception is characterized by known asymmetries in the visual field; humans visual sensitivity is higher along the horizontal than the vertical meridian, and along the lower than the upper vertical meridian. These asymmetries decrease with decreasing eccentricity from the periphery to the center of gaze, suggesting that they may be absent in the 1-deg foveola, the retinal region used to explore scenes at high-resolution. Using high-precision eyetracking and gaze-contingent display, allowing for accurate control over the stimulated foveolar location despite the continuous eye motion at fixation, we investigated fine visual discrimination at different isoeccentric locations across the foveola and parafovea. Although the tested foveolar locations were only 0.3 deg away from the center of gaze, we show that, similar to more eccentric locations, humans are more sensitive to stimuli presented along the horizontal than the vertical meridian. Whereas the magnitude of this asymmetry is reduced in the foveola, the magnitude of the vertical meridian asymmetry is comparable but, interestingly, reversed: objects presented slightly above the center of gaze are more easily discerned than when presented at the same eccentricity below the center of gaze. Therefore, far from being uniform, as often assumed, foveolar vision is characterized by perceptual asymmetries. Further, these asymmetries differ not only in magnitude but also in direction compared to those present just [~]4deg away from the center of gaze, resulting in overall different foveal and extrafoveal perceptual fields.

neuroscience↗

bioRxiv2024

High refresh rate display for natural monocular viewing in AOSLO psychophysics experiments

By combining an external display operating at 360 frames per second with an Adaptive Optics Scanning Laser Ophthalmoscope (AOSLO) for human foveal imaging, we demonstrate color stimulus delivery at high spatial and temporal resolution in AOSLO psychophysics experiments. A custom pupil relay enables viewing of the stimulus through a 3-mm effective pupil diameter and provides refractive error correction from -8 to +4 diopters. Performance of the assembled and aligned pupil relay was validated by measuring the wavefront error across the field of view and correction range, and the as-built Strehl ratio was 0.64 or better. High-acuity stimuli were rendered on the external display and imaged through the pupil relay to demonstrate that spatial frequencies up to 54 cycles per degree, corresponding to 20/11 visual acuity, are resolved. The completed external display was then used to render fixation markers across the field of view of the monitor, and a continuous retinal montage spanning 9.4 by 5.4 degrees of visual angle was acquired with the AOSLO. We conducted eye-tracking experiments during free-viewing and high-acuity tasks with polychromatic images presented on the external display. Sub-arcminute eye position uncertainty was achieved, enabling precise localization of the line of sight on the monitor while simultaneously imaging the fine structure of the human central fovea. This high refresh rate display overcomes the temporal, spectral, and field of view limitations of AOSLO-based stimulus presentation, enabling natural monocular viewing of stimuli in psychophysics experiments conducted with AOSLO.

bioengineering↗