Phosphene perceptions and safety of chronic visual cortex stimulation in a blind subject
Abstract
Stimulation of primary visual cortices has the potential to restore some degree of vision to blind individuals. Developing safe and reliable visual cortical prostheses requires assessment of the long-term stability, feasibility, and safety of generating stimulation-evoked perceptions.A NeuroPace responsive neurostimulation system was implanted in a blind individual with an 8-year history of bare light perception, and stimulation-evoked phosphenes were evaluated over 19 months (41 test sessions). Electrical stimulation was delivered via two four-contact subdural electrode strips implanted over the right medial occipital cortex. Current and charge thresholds for eliciting visual perception (phosphenes) were measured, as were the shape, size, location, and intensity of the phosphenes. Adverse events were also assessed.Stimulation of all contacts resulted in phosphene perception. Phosphenes appeared completely or partially in the left hemifield. Stimulation of the electrodes below the calcarine sulcus elicited phosphenes in the superior hemifield and vice versa. Changing the stimulation parameters of frequency, pulse width, and burst duration affected current thresholds for eliciting phosphenes, and increasing the amplitude or frequency of stimulation resulted in brighter perceptions. While stimulation thresholds decreased between an average of 5% and 12% after 19 months, spatial mapping of phosphenes remained consistent over time. Although no serious adverse events were observed, the subject experienced mild headaches and dizziness in three instances, symptoms that did not persist for more than a few hours and for which no clinical intervention was required.Using an off-the-shelf neurostimulator, the authors were able to reliably generate phosphenes in different areas of the visual field over 19 months with no serious adverse events, providing preliminary proof of feasibility and safety to proceed with visual epicortical prosthetic clinical trials. Moreover, they systematically explored the relationship between stimulation parameters and phosphene thresholds and discovered the direct relation of perception thresholds based on primary visual cortex (V1) neuronal population excitation thresholds.
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The effects found by Fernández et al., 2021 are consistent with findings by other studies reporting brighter phosphenes for higher stimulation strengths and lower stimulation efficiency for longer pulse trains or higher pulse widths and frequencies.
“Note that the effects found by Fernández et al., 2021 (that were modeled by us) are consistent with findings by other studies, which report brighter phosphenes for higher stimulation strengths (Schmidt et al., 1996), and a lower stimulation efficiency (i.e. higher total charge thresholds) for longer pulse trains or higher pulse widths and frequencies (Niketeghad et al., 2020).”
From Towards biologically plausible phosphene simulation for the differentiable optimization of visual cortical prostheses (2024) · cites this paper as Niketeghad et al., 2020
The present results support previous findings and show that the border between V1 and V2, located near the occipital pole, is a suitable place for a cortical visual prosthesis.
“Our present results support previous findings (5, 10, 38, 39, 41, 42) and show that the border between V1 and V2, which is located near the occipital pole, is a suitable place for a cortical visual prosthesis (37).”
From Visual percepts evoked with an intracortical 96-channel microelectrode array inserted in human occipital cortex (2021) · cites this paper as [38]
Previous studies in monkeys and humans demonstrated that the thresholds for phosphene perception in areas V1 and V2 are similar and that the quality of the percepts elicited is comparable.
“Previous studies in monkeys and humans demonstrated that the thresholds for phosphene perception in areas V1 and V2 are similar and that the quality of the percepts that are elicited are comparable (14, 3840).”
From Visual percepts evoked with an intracortical 96-channel microelectrode array inserted in human occipital cortex (2021) · cites this paper as [38]
Large surface electrodes interacted with relatively large volumes of cortex (~1 cm3), resulting in very low spatial resolution of the perceived phosphenes.
“In addition, these large electrodes interacted with relatively large volumes of cortex (∼1 cm3), resulting in very low spatial resolution of the perceived phosphenes (Christie et al., 2016; Niketeghad et al., 2019).”
From Toward Long-Term Communication With the Brain in the Blind by Intracortical Stimulation: Challenges and Future Prospects (2020) · cites this paper as Niketeghad et al., 2019
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- Authors
- Niketeghad, S., Muralidharan, A., Patel, U., Dorn, J. D., Bonelli, L., Greenberg, R. J., & Pouratian, N.
- Affiliations
- University of California, Los Angeles (US)
- Second Sight Medical Products (US)
- Departments of Ophthalmology and
- ORCID
- Venue
- Journal of Neurosurgery
- Published
- 2020-06
- Volume
- 132
- Issue
- 6
- Pages
- 2000-2007
- ISSN
- 0022-3085 (ISSN-L)
- 1933-0693
- OpenAlex
- W2947080206
- Cited by
- 33
- References
- 16
- Citations by year
- 2026: 5 · 2025: 4 · 2024: 3 · 2023: 3 · 2022: 6 · 2021: 8 · 2020: 4
- FWCI
- 2.16
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- Journal of neurosurgery (publishedVersion)
- PubMed (publishedVersion)
- Topics
- Life Sciences › Neuroscience › Cellular and Molecular Neuroscience › Neuroscience and Neural Engineering
- Life Sciences › Neuroscience › Cognitive Neuroscience › Tactile and Sensory Interactions
- Health Sciences › Medicine › Anesthesiology and Pain Medicine › Pain Management and Treatment
- Keywords
- phosphenes, visual cortex stimulation, blindness, visual prosthesis, primary visual cortex, stimulation threshold, calcarine sulcus, stimulation parameters, responsive neurostimulation, subdural electrodes
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