fMRI shows blind patients with retinal implants respond to cues

Functional MRI (fMRI) research showed patients with blindness caused by retinitis pigmentosa had increased brain activity from visual stimuli after receiving retinal prosthetic implants.

The study, by researchers at the University of Pisa in Italy and published in PLOS Biology, illustrated the adult brain can perceive visual cues, such as light flashes, many years after a person has gone totally blind, based on Blood Oxygenation Level Dependent (BOLD) activity.

The fMRI documented increased activity in the brain for patients with implants. As testing continued, activity increased, meaning the more exposure patients had to visual stimuli, the better their brains were at perceiving the cues.

“They show that the adult brain is able to reorganize itself to adapt to the new incoming visual stimulation even after years of blindness. This takes place only after extensive training and well before proper perception is achieved. The BOLD signal is more sensitive than a perceptual threshold or EEG measure to monitor these changes,” the study said. “The reason for the superiority of BOLD in monitoring these changes might be that signals from multiple sources, both bottom-up and top-down, are integrated within the BOLD response and over long periods. In addition, this also indicates that some activity related to the visual stimulus reaches the cortex in RP patients despite complete blindness.”

While the researchers caution this is far from a “cure” for blindness, it would make such efforts worthwhile, because scientists had questioned whether a blind person’s brain could regain the ability to process visual stimuli after having lost their sight.