Georgetown University Medical Center neuroscientists conducted a study helping individuals who are blind from birth the ability to “see” for the first time, revealing critical clues about how the human brain functions.
Investigators say their study, which uses a “sensory substitution device” to help the blind convert visual stimuli into auditory signals, shows that these participants use the same place in the visual cortex as sighted people — the fusiform face area (FFA) — to process facial images.
The fact that blind persons used the FFA to see a facial shape upends a common theory about the way the brain is organized in a person who has never been able to see.
Paula Plaza, PhD, a postdoctoral researcher in the Laboratory of Integrative Neuroscience and Cognition, led by Josef Rauschecker, PhD, a professor physiology and biophysics
Plaza is presenting their findings at the Society for Neuroscience’s annual meeting October 18, 2023 in Washington, DC. The neuroscientists made their discovery by asking blind participants wearing the device to look at cartoon drawings of faces — such as a smiley or sad face with two dots for eyes and a mouth represented by a line curved up or down — while lying in a magnetic resonance image (MRI) scanner.
“Many researchers hypothesize that because, in the blind, vision does not need to be processed, the visual cortex loses its role in vision,” says Plaza. “The theory is that the visual cortex switches from processing vision to becoming a general processor for other senses, especially sound. But our observation in this study is that while the visual cortex does help process other senses in the blind, that area still retains its original function. In the blind, the FFA in the visual cortex is using sound instead of vision to recognize faces. It has not lost its ability to recognize faces, it just is using a different input.”
Rauschecker’s lab is focused on mapping the entire brain, decoding what parts of the brain are involved in various tasks, and how the brain works together as a network.
The study involved seven blind participants from a pool of individuals who have long participated with scientists in Rauschecker’s lab. The device, created in the lab, is a camera attached to goggles. Each pixel in the image is associated with a frequency. For example, pixels at the bottom field of view are low frequency, and at the top are high frequency. Pixels on the left side are lower in tone than pixels on the right. Trained participants often move their heads to obtain the image, either a cartoon face or the shape of a house.
Blind study volunteer Jeannette Gerrard was amazed the first time she “saw” a smile. “Oh wow… it was wonderful. I recognized it! It was like learning something new and, Praise the Lord, I was able to identify it,” she says.
The 65-year-old Washington resident understands that the device is for research, and acknowledges that most of the studies she avidly participates in at Georgetown and the National Institutes of Health will not impact her. “It could help someone else who’s had brain trauma. It’s not for me.”
The device will not be able to help the blind see in such a manner that will improve quality of life, but with training it may help the blind improve their balance, which depends on visual cues, Plaza says.
In addition to Plaza and Rauschecker, co-authors include Laurent Renier and Anne De Volder from Université Catholique de Louvain, Belgium.
The authors report having no personal financial interests related to the study.
This work is supported by a grant from the National Institutes of Health (R01 EY018923).