The Future Of Brain-Computer Interfaces

Hodak describes Prima, a 2-by-2-millimeter implant placed under the retina. Glasses project laser light onto its solar-cell array, stimulating retinal cells and restoring a visual signal for people who have lost photoreceptors. A European trial across 17 sites showed a substantial effect, and Science is seeking approval.

Hodak sees BCIs as a broad category, with different technologies suited to restoring sight, hearing, or movement and potentially to other uses. Because implanted devices require serious brain surgery, he says early users will likely be people with significant disabilities, for whom even basic restored function can justify the risks. He expects the balance to change as devices become more capable.

Hodak says the brain has critical periods in early development, but remains capable of learning through feedback in adulthood. He describes experiments where people learned to control individual neurons after seeing their activity, and explains how BCI users can adapt as a decoder translates neural activity into cursor movement. For Prima users, rehabilitation helps distinguish implant-generated visual signals from percepts the brain produces on its own.

Hodak contrasts Prima’s stimulation of bipolar cells with Second Sight’s stimulation of retinal ganglion cells. The ganglion cells carry signals that have already been compressed into features such as edges and motion, so projecting an image there can produce flashes rather than coherent form vision. Stimulating bipolar cells preserves an earlier stage of retinal processing, which the trial showed could produce recognizable images.

Hodak outlines three areas at Science: retinal implants, neural interfaces, and vessel perfusion. For a future biohybrid interface, the company seeds an implant with engineered stem-cell-derived neurons that may form biological connections with the brain; this approach has been demonstrated in animal models, not humans. He also argues that making perfusion systems smaller and easier to use could help patients who need long-term support outside an intensive care unit.