Biology subjects

Poltoratski, S.

Publications and source records attributed to Poltoratski, S..

3 recordsLinked to original sources

bioRxiv2020

Holistic face recognition is an emergent phenomenon of spatial integration in face-selective regions

Spatial processing by receptive fields is a core property of the visual system. However, it is unknown how spatial coding in high-level regions contributes to recognition behavior. As face inversion is thought to disrupt typical holistic processing of information in faces, we mapped population receptive fields (pRFs) with upright and inverted faces in the human visual system. In face-selective regions, but not primary visual cortex, pRFs and overall visual field coverage were smaller and shifted downward in response to face inversion. From these measurements, we successfully predicted the relative behavioral detriment of face inversion at different positions in the visual field. This correspondence between neural measurements and behavior demonstrates how spatial integration in face-selective regions enables holistic processing. These results not only show that spatial processing in high-level visual regions is dynamically used towards recognition, but also suggest a powerful approach for bridging neural computations by receptive fields to behavior.

neuroscience↗

bioRxiv2020

Differential spatial processing in ventral and lateral face-selective regions is scaffolded by structural connections

Face-processing occurs across ventral and lateral visual streams, which are involved in static and dynamic face perception, respectively. However, the nature of spatial computations across streams is unknown. Using functional MRI and novel population receptive field (pRF) mapping, we measured pRFs in face-selective regions. Results reveal that spatial computations by pRFs in ventral face-selective regions are concentrated around the center of gaze (fovea), but spatial computations in lateral face-selective regions extend peripherally. Diffusion MRI reveals that these differences are mirrored by a preponderance of white matter connections between ventral face-selective regions and foveal early visual cortex (EVC), while connections with lateral regions are distributed more uniformly across EVC eccentricities. These findings suggest a rethinking of spatial computations in face-selective regions, showing that they vary across ventral and lateral streams, and further propose that spatial computations in high-level regions are scaffolded by the fine-grain pattern of white matter connections from EVC.

neuroscience↗

bioRxiv2019

Resolving the spatial profile of figure enhancement in human V1 through population receptive field modeling

The detection and segmentation of meaningful figures from their background is a core function of vision. While work in non-human primates has implicated early visual mechanisms in this figure-ground modulation, neuroimaging in humans has instead largely ascribed the processing of figures and objects to higher stages of the visual hierarchy. Here, we used high-field fMRI at 7Tesla to measure BOLD responses to task-irrelevant orientation-defined figures in human early visual cortex, and employed a novel population receptive field (pRF) mapping-based approach to resolve the spatial profiles of two constituent mechanisms of figure-ground modulation: a local boundary response, and a further enhancement spanning the full extent of the figure region that is driven by global differences in features. Reconstructing the distinct spatial profiles of these effects reveals that figure enhancement modulates responses in human early visual cortex in a manner consistent with a mechanism of automatic, contextually-driven feedback from higher visual areas. Significance StatementA core function of the visual system is to parse complex 2D input into meaningful figures. We do so constantly and seamlessly, both by processing information about visible edges and by analyzing large-scale differences between figures and background. While influential neurophysiology work has characterized an intriguing mechanism that enhances V1 responses to perceptual figures, we have a poor understanding of how the early visual system contributes to figure-ground processing in humans. Here, we use advanced computational analysis methods and high-field human fMRI data to resolve the distinct spatial profiles of local edge and global figure enhancement in the early visual system (V1 and LGN); the latter is distinct and consistent a mechanism of automatic, stimulus-driven feedback from higher-level visual areas.

neuroscience↗