Summary: Researchers have developed an advanced closed-loop visual neuroprosthesis that communicates bidirectionally with the brain, representing a major advance toward restoring functional vision. Unlike previous systems that only delivered stimulation, this implant both stimulates and records neural activity in real time, allowing the device and the brain to adapt to one another.
In two blind volunteers, the implant produced stable, controllable visual percepts that enabled recognition of shapes, motion, patterns, and letters. Although this technology remains under development, the results point to a feasible path for restoring usable vision for people who lost sight because of retinal or optic nerve damage.
Key Facts
- Closed-loop breakthrough: The prosthesis both stimulates the visual cortex and records nearby neural responses, enabling adaptive stimulation that more closely mimics natural vision.
- Functional outcomes: Implanted participants were able to perceive shapes, movement, patterns, and some letters — a clear advance beyond simple phosphenes or flashes of light.
- Minimally invasive implantation: A 4 mm microelectrode array containing 100 electrodes was inserted using robotic guidance through an 8–10 mm opening, reducing surgical impact and recovery time.
Source: UMH
The impact of blindness
Blindness profoundly alters daily life. Several research groups worldwide, including the Biomedical Neuroengineering Lab at Miguel Hernández University of Elche (UMH), are developing cortical visual prostheses that aim to restore practical vision for people who once saw but lost their sight due to retinal degeneration or optic nerve injury.
A recent study published in Science Advances presents results from UMH demonstrating a new class of bidirectional cortical visual prostheses. By establishing real-time two-way communication with the visual cortex, the system creates an adaptive dialogue between electronics and the brain, bringing artificial vision closer to its biological counterpart.
“A cortical artificial vision system seeks to emulate how natural vision works,” says Eduardo Fernández Jover, UMH professor and lead investigator. The system uses an external camera mounted on ordinary-looking glasses to capture the visual scene. That video feed is processed and translated into electrical stimulation patterns delivered to the occipital cortex, the brain’s visual processing area.
Crucially, vision is not a one-way process. Natural sight depends on continuous feedback between the eyes and brain. Open-loop implants ignore this feedback and cannot compensate when neural responses change. The new closed-loop approach records local neural activity while stimulating and automatically adjusts parameters in response. “The system writes to the brain and reads from it,” Fernández Jover explains. “That lets the device and the cortex learn from one another.”
The implanted array measures 4 millimeters across and contains 100 microelectrodes. Surgeons used robotic assistance and neuronavigation to place the array through a small opening of 8–10 millimeters, avoiding a full craniotomy. According to Pablo González López, neurosurgeon at Hospital Doctor Balmis and IMED Hospitals, this technique permits precise, real-time guidance of the electrodes while reducing postoperative discomfort and shortening hospital stays.
Earlier efforts produced phosphenes — brief flashes perceived as points of light — but achieving meaningful, stable visual percepts has been challenging. This study shows that by recording neural responses near the stimulating electrodes, researchers can predict perceptual outcomes such as threshold, perceived brightness, and the minimum interval needed to distinguish separate stimuli. That predictive power enables automatic fine-tuning of stimulation to improve performance and accelerate user learning.
Thanks to the bidirectional exchange, the implanted volunteers could recognize complex patterns, detect motion, and identify some letters, demonstrating functional vision capabilities beyond simple light perception. The team reports that stimulation parameters can be adjusted in real time to maintain consistent percepts despite changes in neural sensitivity or adaptation.
These advances are an encouraging step toward practical cortical visual prostheses that might one day improve mobility, navigation, and daily function for people with acquired blindness. Fernández Jover cautions that the work remains preliminary: “The results are promising, but many challenges remain. We must proceed carefully and avoid creating unrealistic expectations.”
Importantly, this approach targets individuals who previously had vision and whose visual cortex retains circuitry for interpreting visual signals. For people who are congenitally blind, the visual cortex often reorganizes for other functions, limiting the ability to decode artificial visual input with current methods.
The research team includes Fabrizio Grani, Cristina Soto Sánchez, Alfonso Rodil Doblado, Rocío López Peco, and Eduardo Fernández Jover from the UMH Bioengineering Institute, together with neurosurgeon Pablo González López from Hospital General Universitario Dr. Balmis in Alicante. The investigators acknowledge the volunteer participants, their families, and clinical staff at IMED Elche Hospital for their sustained commitment to the project.
Funding: This work received support from the Ministry of Science, Innovation and Universities (DTS19/00175, PDC2022-133952-100); the European Union’s Horizon 2020 program (grant agreements no. 899287 NeuraViPeR and no. 861423 enTRAIN Vision; Innovative Neurotechnology for Society (INTENSE)); the Dutch Neurotechnology Consortium; and the Regional Government of Valencia (PROMETEO CIPROM/2023/25).
Key Questions Answered:
A: They developed a closed-loop visual neuroprosthesis that both stimulates the visual cortex and records neural responses in real time, creating a two-way dialogue with the brain.
A: Earlier systems were open-loop and did not adjust to changing neural responses. The new device adapts stimulation based on recorded brain activity, more closely resembling natural vision.
A: Implanted volunteers were able to recognize shapes, motion, patterns, and some letters, demonstrating functional percepts beyond simple flashes of light.
About this neurotech and visual neuroscience research news
Author: Angeles Gallar
Source: UMH
Contact: Angeles Gallar – UMH
Image: Image credited to Neuroscience News
Original Research: Open access. “Neural correlates of phosphene perception in blind individuals: A step toward a bidirectional cortical visual prosthesis” by Eduardo Fernández Jover et al., Science Advances.
Abstract
Neural correlates of phosphene perception in blind individuals: A step toward a bidirectional cortical visual prosthesis
Blindness is one of the most consequential disabilities for affected individuals. Cortical prostheses could one day restore functional vision for some blind people, but success will require integrating advanced technologies to deliver reliable therapeutic benefits. Most prior human studies used electrodes only for stimulation, which makes precise control over individual phosphenes difficult.
In this work, researchers implanted an intracortical microelectrode array of 100 electrodes in the visual cortex of two blind volunteers. They recorded local neural activity while delivering electrical stimulation to evoke visual percepts. The results demonstrate how stimulation parameters influence perceptual thresholds, perceived brightness, and the temporal resolution required to separate stimuli. Crucially, subjective visual experience could be predicted from recorded neural signals, suggesting that nearby neural activity can be used to infer and control percepts in cortical visual prostheses.