Intracortical microstimulation evokes diverse electrode-specific phosphenes in the early visual cortex of blind individuals
- 1University Miguel Hernandez
Abstract
PurposeElectrical stimulation of the occipital cortex evokes visual percepts known as phosphenes. To date, most human studies have examined phosphenes elicited by large surface or depth electrodes. These differ considerably from the small penetrating intracortical microelectrodes capable of stimulating highly localized cortical populations that are the basis of current next-generation devices. Here, we provide a detailed characterization of phosphenes evoked by such intracortical microelectrodes.
MethodsAs part of the CORTIVIS clinical trial, a Utah Electrode Array with 100 penetrating electrodes was implanted in the early visual cortex of four blind volunteers. Participants completed drawing and description tasks in response to single-electrode stimulation. Two participants also performed forced-choice tasks to determine whether phosphenes elicited by different electrodes could be reliably discriminated.
ResultsSingle-electrode stimulation reliably evoked phosphenes in all participants. Most percepts appeared in the contralateral visual field, although two participants reported near-midline ipsilateral percepts. Phosphenes ranged from simple dots to elongated, textured, circular, or otherwise idiosyncratic forms. One participant reported distinguishable phosphene colors, which depended on electrode and amplitude structure and varied across sessions. The two participants tested on forced-choice discrimination could successfully identify electrode-specific phosphenes across multiple sessions.
ConclusionsIntracortical microstimulation of the human visual cortex produces phosphenes with diverse, electrode-specific appearances that are recognizable across repeated trials. These findings indicate that penetrating microelectrodes often evoke more structured percepts than simple points or blobs, providing foundational evidence that electrode-specific encoding strategies will be necessary in future visual prosthetic devices.
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BibTeX
@misc{soo2026intracortical,
title = {{Intracortical microstimulation evokes diverse electrode-specific phosphenes in the early visual cortex of blind individuals}},
author = {L. Soo and A. Rodil Doblado and F. Grani and R. Lopez Peco and A. Villamarin-Ortiz and R. Morollon Ruiz and D. Waclawczyk and I. Fine and P. Gonzalez-Lopez and C. Soto-Sanchez and A. Alfaro and E. Fernandez},
howpublished = {medRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.05.26364412},
url = {https://www.medrxiv.org/content/10.64898/2026.10.05.26364412v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Intracortical microstimulation evokes diverse electrode-specific phosphenes in the early visual cortex of blind individuals
AU - L. Soo
AU - A. Rodil Doblado
AU - F. Grani
AU - R. Lopez Peco
AU - A. Villamarin-Ortiz
AU - R. Morollon Ruiz
AU - D. Waclawczyk
AU - I. Fine
AU - P. Gonzalez-Lopez
AU - C. Soto-Sanchez
AU - A. Alfaro
AU - E. Fernandez
PY - 2026
DA - 2026/10/05
PB - medRxiv
DO - 10.64898/2026.10.05.26364412
UR - https://www.medrxiv.org/content/10.64898/2026.10.05.26364412v1
AB - PurposeElectrical stimulation of the occipital cortex evokes visual percepts known as phosphenes. To date, most human studies have examined phosphenes elicited by large surface or depth electrodes. These differ considerably from the small penetrating intracortical microelectrodes capable of stimulating highly localized cortical populations that are the basis of current next-generation devices. Here, we provide a detailed characterization of phosphenes evoked by such intracortical microelectrodes. MethodsAs part of the CORTIVIS clinical trial, a Utah Electrode Array with 100 penetrating electrodes was implanted in the early visual cortex of four blind volunteers. Participants completed drawing and description tasks in response to single-electrode stimulation. Two participants also performed forced-choice tasks to determine whether phosphenes elicited by different electrodes could be reliably discriminated. ResultsSingle-electrode stimulation reliably evoked phosphenes in all participants. Most percepts appeared in the contralateral visual field, although two participants reported near-midline ipsilateral percepts. Phosphenes ranged from simple dots to elongated, textured, circular, or otherwise idiosyncratic forms. One participant reported distinguishable phosphene colors, which depended on electrode and amplitude structure and varied across sessions. The two participants tested on forced-choice discrimination could successfully identify electrode-specific phosphenes across multiple sessions. ConclusionsIntracortical microstimulation of the human visual cortex produces phosphenes with diverse, electrode-specific appearances that are recognizable across repeated trials. These findings indicate that penetrating microelectrodes often evoke more structured percepts than simple points or blobs, providing foundational evidence that electrode-specific encoding strategies will be necessary in future visual prosthetic devices.
ER -