Even though blind people cannot see, they often have the brain regions that allow them to see. Does this mean that blind people can dream with visual images?
In some cases, they can. A 2014 study found that people who were not born blind but lost their sight later in life sometimes report visual experiences in their dreams. These dreams were probably drawn from memories of the times when they could still see. However, the earlier a person loses their sight and the longer they remain blind, the less likely they are to see images in their dreams, the study notes.
“A person blind at age 7 or earlier, who has been blind for, say, 20 years, loses virtually all visual experiences of their dreams,” study co-author. Maurice Ptitovisual 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 on other senses such as hearing, touch, taste and smell.” Monique Goricognitive neuroscientist at the Italian Institute of Technology in Genoa, told Live Science.
Most studies suggest that visual experiences are generally absent from the dreams of people blind from birth. “However, a few dream studies have called this notion into question.” Ivana Rosenzweigdirector of the Sleep and Brain Plasticity Center at King’s College London, told Live Science.
Related: Why can’t we remember our dreams?
For example, a 2003 study in the journal Trends in cognitive science reported that people with congenital blindness who were scanned with electrodes on their scalp while sleeping showed signs of brain waves associated with vision. A Study 2023 Rosenzweig and colleagues, who 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 can dream in visual images is the idea that dreams could provide access to experiences that these individuals never had in their waking life.” Helene Vitalicognitive neuroscientist at the Italian Institute of Technology, told Live Science.
However, even though activity may occur in the visual cortex of blind people’s brains when they dream, that does not necessarily mean they are seeing images while they sleep, Ptito said.
“In the congenitally blind, the visual cortex was recruited for other functions,” Ptito said. For example, “in blind people who can read Braille, if you stimulate their visual cortex, they feel a sensation in their fingers. The visual cortex does not stop functioning in blind people: it is reassigned.”
Ptito noted that “we took blind people into fMRI (functional magnetic resonance imaging) scanners and sent smells to their noses while taking pictures of their brains, and found that this information went to their visual cortex .” The same goes for auditory and tactile sensations, he added.
Although Ptito argued that visual cortex activity does not mean that blind people see images during dreams, Vitali suggested other possibilities. The first is that the brain’s visual system can form abstract concepts from a blind person’s senses that could be represented visually to them. Another is that “REM sleep acts like a virtual reality simulator, helping the brain develop and maintain complex abilities such as perception and motor skills,” she said. This could mean that blind people’s brains could generate images in their dreams, even though they could never have such experiences when awake.
One of the major problems in investigating whether congenitally blind people dream in images is that, even if they see images, they have no experience connecting them to what sighted people describe as vision. Christopher Bairdassociate professor of physics at West Texas A&M University, explained in a blog post.
To address this problem, Gori and his colleagues are currently studying how blind people construct and experience dream images. “The results are being finalized and will be available soon,” she said. Ptito also noted that artificial intelligence could one day analyze brain scans of blind people while they dream to see how similar their brain activity is to that of sighted people.
One possible application of this research is the possibility of harnessing dreams as a rehabilitation tool, Vitali said.
“There is evidence that dreaming about certain tasks or experiences can improve memory and learning,” Vitali said. This suggests that “targeting the dream state via sensory stimulation during sleep could help strengthen specific abilities, such as spatial awareness.” This could be a new way to help blind people, because “blind people often face difficulty developing spatial maps and performing complex spatial tasks,” she noted.