Highly accurate retinotopic maps of the physiological blind spot in human visual cortex

Abstract

The physiological blind spot is a naturally occurring scotoma corresponding with the optic disc in the retina of each eye. Even during monocular viewing, observers are usually oblivious to the scotoma, in part because the visual system extrapolates information from the surrounding area. Unfortunately, studying this visual field region with neuroimaging has proven difficult, as it occupies only a small part of retinotopic cortex. Here, we used functional magnetic resonance imaging and a novel datadriven method for mapping the retinotopic organization in and around the blind spot representation in V1. Our approach allowed for highly accurate reconstructions of the extent of an observer's blind spot, and out-performed conventional model-based analyses. This method opens exciting opportunities to study the plasticity of receptive fields after visual field loss, and our data add to evidence suggesting that the neural circuitry responsible for impressions of perceptual completion across the physiological blind spot most likely involves regions of extrastriate cortex-beyond V1.

Retinotopic connectivity maps of human visual cortex with unconstrained eye movements

“…We also conducted a standard forward-modeling pRF analysis [Dumoulin and Wandell, 2008; Moutsiana et al, 2016; Urale et al, 2022] on the data from the Standard Mapping and Unstable Eye experiments. This was to compare our CF estimates to conventional pRF measurements and to evaluate the impact erratic eye-movements have on retinotopic mapping with either method.…”

“…Classical mapping experiments typically present stimuli via a screen mounted onto the head coil inside the scanner bore that only subtends the central 10-20° of the visual field. While some previous single-unit and fMRI studies attempted to minimize this limitation through use of eccentric fixation targets, goggles, telescopes, or spherical projection systems [Jolly et al, 2021; Mikellidou et al, 2017; Pitzalis et al, 2006; Smittenaar et al, 2016; Urale et al, 2022; Yu et al, 2012], the difficulty of such experiments, the requirement for special equipment, and the fact that most of these methods can still not stimulate the far periphery precludes us from studying peripheral visual field maps regularly in humans. This constrains our understanding of conditions affecting peripheral vision, such as glaucoma or hallucinations experienced in a range of disorders, like schizophrenia or neurodegenerative illness like Parkinson’s Disease because these typically occur in the peripheral visual field.…”

Retinotopic connectivity maps of human visual cortex with unconstrained eye movements

“…We also conducted a standard forward‐modeling pRF analysis (Dumoulin & Wandell, 2008 ; Moutsiana et al, 2016 ; Urale et al, 2022 ) on the data from the Standard Mapping and Unstable Eye experiments. This was to compare our CF estimates to conventional pRF measurements and to evaluate the impact erratic eye movements have on retinotopic mapping with either method.…”

“…Classical mapping experiments typically present stimuli via a screen mounted onto the head coil inside the scanner bore that only subtends the central 10–20° of the visual field. While some previous single‐unit and fMRI studies attempted to minimize this limitation through the use of eccentric fixation targets, goggles, telescopes, or spherical projection systems (Jolly et al, 2021 ; Mikellidou et al, 2017 ; Pitzalis et al, 2006 ; Smittenaar et al, 2016 ; Urale et al, 2022 ; Yu et al, 2012 ), the difficulty of such experiments, the requirement for special equipment, and the fact that most of these methods can still not stimulate the far periphery preclude us from studying peripheral visual field maps regularly in humans. This constrains our understanding of conditions affecting peripheral vision, such as glaucoma or hallucinations experienced in a range of disorders, like schizophrenia or neurodegenerative illness like Parkinson's Disease because these typically occur in the peripheral visual field.…”

Cortical sensory aging is layer-specific

“…The fine fit is an optimized procedure to refine the parameters by further maximizing the correlation between observed and predicted time series. The noise ceiling was calculated as an estimate of the maximum goodness-of-fit that could theoretically be achieved from the data of each voxel 104 , using a similar procedure as Urale et al 105 . The Spearman-Brown prophecy formula 106 was used to account for the accurate estimate of the true reliability of the time series.…”