Unused Brain Regions Can Be Repurposed via Neuroplasticity
Parts of the brain designated to vision can be repurposed to hear, if necessary.
Posted Sep 24, 2019
Earlier this month, Psychology Today blogger Harriet Dempsey-Jones wrote a post, "What Happens to Your Brain When You Use Your Feet as Hands?" that reported on a fascinating study (2019) she conducted with colleagues at University College London on how neuroplasticity reshapes the brain in foot artists without hands. Remarkably, foot painters' toes are mapped out like fingers in their brains.
By creating brain maps of artists who were born without either arm and use their feet and toes to make art, Dempsey-Jones and colleagues showed for the first time that the human brain has designated areas in the brain (much like monkeys) that evolved to control the fine-tuned movement of every toe. However, in modern-day, shoe-wearing civilization, these brain areas lie dormant. This lack of use causes atrophy and subsequent pruning to keep the brain streamlined.
Most of us use our fingers to navigate life, create music, and make art. Therefore, we typically have extremely well-organized brain areas designated to each of the 10 digits on our hands used to perform these tasks. Conversely, only a few scattered brain areas are typically designated to the dexterity of our 10 toes.
Dempsey-Jones responded to her team's overarching research question: Did we lose these toe maps or never have them? "Our results make sense from a brain plasticity perspective—if you don’t use your toes separately in action, your brain does not need to represent each toe separately. The results also make sense given our primate cousins have organised toe maps, in a similar brain position and orientation to the artists."
Brain imaging (below) shows that when congenitally blind people hear an audio-movie or listen to a book-on-tape narrative, regions of the cerebral cortex that are typically thought of as "vision only" brain areas light up in the fMRI. These findings were published on September 23 in the Journal of Neuroscience.
In my mind, this new research (2019) on cortical flexibility by author Rita Loiotile of the Johns Hopkins University Department of Psychological and Brain Sciences dovetails with the recent work of Harriet Dempsey-Jones and colleagues regarding toe maps in extreme foot users. Both of these studies illuminate how life circumstances influence how the brain reshapes or rewires its structure and function to perform everyday tasks or create works of art.
Since the early 1800s and the days of phrenology, neuroscientists have been trying to match brain functions with specific locations and to create accurate "brain maps." The biggest problem with mapping the brain is that gray matter and white matter neural architecture are never set in stone—the brain is plastic; it reshapes and rewires itself when necessary.
As another example, last month researchers from Spain reported (François et al., 2019) that if regions in the left hemisphere that are typically responsible for language are damaged at a young age, that unused regions of the right brain can be repurposed and "take over" language functions. (See Study Shows Left Brain–Right Brain Reconfiguration in Action)
For her dissertation at Johns Hopkins on "evidence of extreme cortical flexibility," Rita Loiotile examined just how flexible the visual cortex is by studying if this brain region can be repurposed to carry out other functions as a result of congenital blindness.
Last year, in the conclusion of her dissertation (2018), Loiotile wrote:
"Taken together, this dissertation demonstrates that "visual" cortices of blind individuals are meaningfully repurposed for higher cognitive functions. Though brain structures may seem particularly suited to implement a particular function, such structure-to-function mappings are not evidence of functional rigidity. In contrast, evidence from blindness suggests that human cortex is highly flexible at birth."
In her most recent study (2019) on the repurposing of unused brain regions, Loiotile and her JHU colleagues used whole-cortex analysis to compare synchronization across different brain regions in blind and blindfolded sighted study participants as they listened to audio-movie clips and an auditory narrative.
As mentioned, the majority of blind individuals used parts of the cerebral cortex that are typically used for vision when they listened to audio-movies or a "book on tape" type of Audible narrative.
"A direct comparison revealed higher inter-subject synchronization for audio-movies within the primary "visual" cortices of the blind group," the authors write in the paper's conclusion. "The audio-track of movies drove collective responding in 65 percent of the "visual" cortices, by surface area. Synchronization was observed bilaterally [in both cerebral hemispheres]. The current findings are consistent with the idea that, in blindness, most of the available cortical tissue undergoes systematic adaptation for everyday tasks."
In her memoir, The Story of My Life, Helen Keller, who was deaf and blind, describes how books spoke to her, "They took away what should have been my eyes (but I remembered Milton's Paradise) ... Literature is my Utopia. Here I am not disenfranchised. No barrier of the senses shuts me out from the sweet, gracious discourses of my [books]. They talk to me without embarrassment or awkwardness."
If Keller were alive today, it would be interesting to see what parts of her brain lit up in an fMRI when she interpreted literature through her fingertips reading Braille.
In closing, below is another quote from Keller that reminds us how important it is to soak up the world using whatever senses we have at our disposal:
"I who am blind can give one hint to those who see: Use your eyes as if tomorrow you would be stricken blind. And the same method can be applied to the other senses. Hear the music of voices, the song of a bird, the mighty strains of an orchestra, as if you would be stricken deaf tomorrow. Smell the perfume of flowers, taste with relish each morsel, as if tomorrow you could never smell and taste again. Make the most of every sense." —Helen Keller (1880-1968)
Rita Loiotile, Rhodri Cusack and Marina Bedny. "Naturalistic Auditory Stories Synchronize "Visual" Cortices Across Congenitally Blind but Not Sighted Individuals" Journal of Neuroscience (First Published: September 23, 2019) DOI: 10.1523/JNEUROSCI.0298-19.2019
Harriet Dempsey-Jones, Daan B. Wesselink, Jason Friedman, Tamar R. Makin. "Organized Toe Maps in Extreme Foot Users" Cell Reports (First published: September 10, 2019) DOI: 10.1016/j.celrep.2019.08.027
Clément François, Pablo Ripollés, Laura Ferreri, Jordi Muchart, Joanna Sierpowska, Carme Fons, Jorgina Solé, Monica Rebollo, Robert J Zatorre, Alfredo Garcia-Alix, Laura Bosch and Antoni Rodriguez-Fornells. "Right Structural and Functional Reorganization in 4-Year-Old Children with Perinatal Arterial Ischemic Stroke Predict Language Production." eNeuro (First published: August 5, 2019) DOI: 10.1523/ENEURO.0447-18.2019