High-channel-count neuroprostheses could one day restore functional vision in blind individuals by delivering electrical pulses to electrodes in the visual cortex that elicit perceptions known as phosphenes. However, if a high number of electrodes are used, it becomes challenging and time-consuming to map the visual field locations of all phosphenes. Furthermore, many blind users are not able to maintain stable fixation, impeding the localization of phosphenes, or may perceive spontaneous visual phenomena that interfere with detection of electrically induced phosphenes. Here, we introduce NEural Unsupervised electrode mapping (NEUmap), a rapid, largely automated method for phosphene mapping that extracts spatial patterns in spontaneous activity across the visual cortex. As correlations between neuronal activity on nearby electrodes are stronger than those between distant electrodes, we first use dimensionality-reduction algorithms to generate maps of relative positions of electrodes. We then convert these maps from relative to absolute visual field coordinates while the subject maps out a small number of phosphenes manually. NEUmap generated maps across ~300-700 electrodes in each of two sighted monkeys and across 73-91 electrodes in each of three blind human volunteers. We report that the method allows rapid mapping of many electrodes using less than a second of resting-state data, with minimal effort from the subject, in the absence of vision.

PR and XC are co-founders and shareholders of a neurotechnology start-up, Phosphoenix (Netherlands) (https://phosphoenix.nl).

NCT02983370

This work was supported in part by NWO (STW grant number P15-42 NESTOR, Crossover grant number 17619 INTENSE and DBI2, a Gravitation program of the Dutch Ministry of Science, Education and Culture), ZonMW grant 09120232310021 EVISION, the European Union Horizon 2020 program (ERC grant number 101052963 NUMEROUS, FET-Open grant number 899287 NeuraViPeR), the LSH Match Project LSHM23002 (POSITIONED), and by grants DTS19/00175 and PDC2022-133952-100 from the Spanish Ministerio de Ciencia, Innovacion y Universidades.

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The study protocol with three human participants was approved by the Clinical Research Committee at the Hospital General Universitario de Elche (ClinicalTrials.gov registration number NCT02983370, CORTIVIS). All ethical guidelines conformed with clinical trial regulations (EU No. 536/2014 [repealing Directive 2001/20/EC], the Declaration of Helsinki, and the EU Commission Directives 2005/28/EC and 2003/94/EC), and we obtained written informed consent from the subjects prior to the study.

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