Do blind people 'see' images in their dreams?
Although blind people cannot see, they often still possess the brain regions that enable vision. Does this mean that blind people can dream in visual images?
In some cases, they can. A 2014 study found that people who were not born blind but had lost their vision later in life sometimes reported visual experiences in their dreams. These dreams likely drew from memories from when they still had sight. However, the earlier a person had lost their vision in life, and the longer they were blind, the less likely they were to see images in dreams, the study noted.
"A person blind at age 7 or before who has been blind for, say, 20 years, loses virtually all visual experiences in their dreams," study co-author Maurice Ptito, a visual neuroscientist at the University of Montreal, told Live Science.
When it comes to people who are congenitally blind — those born without vision — "dreams tend to rely more heavily on other senses such as hearing, touch, taste and smell," Monica Gori, a cognitive neuroscientist at the Italian Institute of Technology in Genoa, told Live Science.
Most studies suggest visual experiences are generally absent in the dreams of those who are blind from birth. "However, there are a few dream studies that have challenged this notion," Ivana Rosenzweig, head of the Sleep and Brain Plasticity Centre at King's College London, told Live Science.
Related: Why can't we remember our dreams?
For instance, a 2003 study in the journal Trends in Cognitive Sciences reported that people with congenital blindness who were scanned with electrodes on their scalps as they slept had evidence of brain waves associated with vision. A 2023 study from Rosenzweig and her colleagues, which analyzed 180 dreams of seven congenitally blind people, also found reports of vision-like descriptions.
"What we find most surprising and exciting about the possibility that congenitally blind individuals might dream in visual images is the idea that dreams could provide access to experiences that these individuals have never encountered in their waking lives," Helene Vitali, a cognitive neuroscientist at the Italian Institute of Technology, told Live Science.
However, although activity may occur in the visual cortex of blind people's brains as they dream, that does not necessarily mean they see images as they sleep, Ptito said.
"In the congenitally blind, the visual cortex has been recruited for other functions," Ptito said. For instance, "with blind people who can read Braille, if you stimulate their visual cortex, they feel sensation in their fingers. The visual cortex does not stop working in blind people — it gets reassigned."
Ptito noted that "we've had blind people in fMRI [functional magnetic resonance imaging] scanners and sent smells to their noses while taking pictures of their brains, and found this information goes to their visual cortex." The same held true with auditory and touch sensations, he added.
Although Ptito argued that activity in the visual cortex does not mean that blind people see pictures during dreams, Vitali suggested other possibilities. One is that the brain's visual system may form abstract concepts from a blind person's senses that might be represented in a visual way for them. Another is that "REM sleep acts like a virtual reality simulator, helping the brain develop and maintain complex abilities like perception and motor skills," she said. This could mean blind people's brains could generate images within dreams even if they could never have such experiences when they are awake.
One key problem with investigating whether congenitally blind people dream in images is that, even if they do see pictures, they have no experience relating them to what sighted people describe as vision, Christopher Baird, an associate professor of physics at West Texas A&M University, explained in a blog post.
To help address this problem, Gori and her colleagues are now exploring how blind people construct and experience dream images. "The results are currently being finalized and will be available soon," she said. Ptito also noted that artificial intelligence may one day analyze brain scans of blind people as they dream to help see how similar their brain activity is to what sighted individuals experience.
One possible application of this research is the potential to harness dreams as a rehabilitative tool, Vitali said.
"There is evidence that dreaming about certain tasks or experiences can enhance memory and learning," Vitali said. This suggests "targeting the dream state through sensory stimulation during sleep could help reinforce specific abilities, such as spatial awareness." This may provide a new way to help people with blindness, as "blind individuals often face challenges in developing spatial maps and performing complex spatial tasks," she noted.
