More than 40 million people worldwide are blind, and many of them reach this condition after many years of low eyesight.
The development of artificial eyes or new light-responsive elements, aiming to replace the disrupted retinal function and to feed restored visual signals to the brain, has provided new hope.
However, very little is known about whether the brain of blind people retains residual capacity to process restored or artificial visual inputs.
In a new study published in PLOS Biology, researchers from the University of Pisa in Italy investigated the brain’s capability to process visual information after many years of total blindness.
They studied patients affected by Retinitis Pigmentosa, an illness of the retina that gradually leads to complete blindness.
The perceptual and brain responses of a group of patients were tested before and after the implantation of an artificial eye.
The implant could sense visual signals and transmits them to the brain by stimulating axons of retinal ganglion cells.
Using functional magnetic resonance imaging (fMRI), the researchers found that patients learned to recognize unusual visual stimuli, such as flashes of light, and this ability correlated with increased brain activity.
However, this change in brain activity, observed at both the thalamic and cortical level, took extensive training over a long time to become established.
Basically, the more the patient practiced, the more their brain responded to visual stimuli, and the better they perceived the visual stimuli using the implant. In other words, the brain needs to learn to see again.
The results are important. After the implantation of an artificial eye, the brain undergoes changes to re-learn how to make use of the new artificial and probably aberrant visual signals.
The study demonstrates a remained plasticity of the sensory circuitry in the adult brain after many years of deprivation. This can be helpful in the development of new artificial eyes.
Citation: Castaldi E, et al. (2016). Visual BOLD Response in Late Blind Subjects with Argus II Retinal Prosthesis. PLOS Biology, published online. DOI:10.1371/journal.pbio.1002569.
Figure legend: This Knowridge.com image is credited to Castaldi E et al.