Biology subjects

Scialom, E.

Publications and source records attributed to Scialom, E..

3 recordsLinked to original sources

bioRxiv2025

Mid-level visual features engage V4 to support sparse object recognition under uncertainty

Cortical visual prostheses aim to restore sight by stimulating the visual cortex, yet current approaches remain limited. Implants targeting V1 typically evoke isolated phosphenes that do not support coherent object recognition. We asked whether mid-level visual features, specifically curve segments associated with area V4, could provide a more efficient substrate for artificial vision. Using fMRI, 24 participants performed an object recognition task with stimuli fragmented into either phosphene-like dots or curve segments at varying densities. Behaviorally, curve segments enabled recognition at lower density thresholds and produced steeper psychometric slopes. Neurally, both fragment types engaged V1, but only curve segments recruited V4, and correct recognition of segments relative to phosphenes evoked broader occipito-temporo-parietal responses. Multivariate decoding showed that successful recognition of phosphenes was predicted by early visual and cingulate activity, whereas recognition of segments was predicted only by V4, indicating a shift toward mid-level representational support. Mediation analyses further showed that phosphene-based recognition relied on anterior cingulate cortex under conditions of higher uncertainty, while segment-based recognition depended primarily on visual cortex. Together, these results show that mid-level fragments confer perceptual and neural advantages, reducing reliance on both dense stimulation and downstream uncertainty resolution, and identify V4 as a promising target for next-generation cortical prostheses.

neuroscience↗

bioRxiv2025

Wide visual angle enhances social interaction in a realistic virtual reality environment under simulated artificial vision

Objective. Social interaction largely relies on visual perception. Yet artificial vision research has primarily focused on navigation and object recognition while assessment of social interaction remains scarce. This study investigates how the visual field size in simulated artificial vision impacts social perception in a virtual reality setting. Approach. We assessed the impact of visual field size in sighted participants experiencing simulated artificial vision in a medical practice across three social task categories: indoor identification (searching for an empty chair, identification of body orientation, body appearance, facial expressions, relationship type, role and interpretation of body language), locomotion (tracking and following a moving person), and outdoor observation (person recognition in a cluttered outdoor environment). Main Results. A wide range of social perception and locomotion tasks in structured indoor environments can be completed with a 45{degrees} field of view in simulated artificial vision. Compared to 20{degrees}, the broader visual field not only enhances accuracy but also enables faster task execution and a more precise assessment of ones own performance. Although the benefits of an expanded visual field are limited in cluttered environments, a 45{degrees} visual field represents a clear advantage in social contexts. Significance. These findings highlight the importance of an expanded visual field for artificial vision users in social settings, reinforcing its role in enhancing social cue processing and the ability to follow people. By integrating simulated artificial vision within an immersive virtual reality framework, this study bridges the gap between controlled experimental paradigms and real-world needs and challenges.

bioengineering↗

bioRxiv2024

Minimizing the number of phosphenes required for object recognition under prosthetic vision

Cortical prostheses offer the potential for partial vision restoration in individuals with blindness by stimulating V1 neurons to produce phosphenes. However, the low number of phosphenes that can be elicited in practice makes encoding of whole objects difficult, and the round shape of phosphenes lack the contour cues necessary for perceptual grouping. We propose a minimalistic encoding approach that focuses on essential visual information. We fragmented objects contours into either phosphenes or curved segments, providing either low or high local visual information. 46 participants identified these fragmented objects in a free-naming task. The number of fragments gradually increased to quantify the minimum number of phosphenes and segments necessary to recognize objects. Most objects could be recognized with only 65 phosphenes, which is in the range of implantable electrodes in human patients. Participants required 27% fewer segments than phosphenes to recognize objects. Including individual objects as a random effect in a linear mixed model substantially increased the explained variance, suggesting that the minimal number of fragments required for object recognition in prosthetic vision strongly depends on the particular object. Our results demonstrate that a minimalistic approach can substantially reduce the number of phosphenes required for recognition, emphasizing the importance of identifying critical object features to minimize brain stimulation in visual prostheses.

neuroscience↗