What happens when the brain is out of a job?

July 2nd, 2024

Written by: Barnes Jannuzi

Flexibility is the key to success, and nothing adapts like the brain. Here we will discuss the brain’s ability to learn and change when disaster strikes, what the brain needs in order to adapt, and how we might one day be able to help our brains to overcome even greater challenges. 

The brain is plastic

No… not the disposable water bottle kind of plastic. Plasticity in neuroscience is the capacity for the brain to reorganize itself and change depending on its needs. The most obvious example of plasticity is the ability to learn; because everything we remember and every skill we develop is a result of changes in the brain. 

Ever notice how children seem to learn much faster than adults? It likely comes as no surprise that children have more plastic brains than adults¹, with this plasticity slowly decreasing with age. While it may not seem like it at first, it is probably a good thing that the adult brain is less plastic for the most part. More plasticity means more changeability, and these changes mean not only learning, but also forgetting. We don’t want everything to change all the time later in life- imagine how annoying it would be to have to constantly forget and relearn how to walk or to read.

However, plasticity is not only critical for learning when the brain and body are healthy, it is also crucial for the brain to be able to change and rearrange when the body is damaged. What happens when something goes very wrong? Let’s dive into an example of how the brain responds when the body can no longer see.

Recycling the pieces

One of the more amazing examples of the brain’s ability to adapt to injury is when individuals lose normal function of their eyes from birth or early in life. In a sighted individual, the eyes observe light and send signals to a brain area near the back of the skull called the occipital lobe. This region typically supports vision and allows the brain to make sense of the signals coming from our eyes. But what happens when the lights go out? When the brain stops getting signals from the eyes (or never starts getting them in the first place) that part of the brain is temporarily out of a job. 

Being the go-getter that the occipital cortex is, it pulls itself up by its nerve straps and finds a way to make itself useful. It learns to read through touch! Amazingly, in individuals who have been blind since birth or early childhood, the occipital cortex is active when those individuals read braille ^2,3,4 (the written language for individuals who are blind, composed of bumps which represent characters that can be “read” through the fingertips.) Not only does the occipital cortex light up with activity when participants feel braille bumps, but when researchers temporarily interfere with part of the occipital cortex, blind participants become worse at reading braille². Intriguingly, these participants can still tell that they are touching braille, they are just worse at determining what the braille reads. In contrast, when researchers interfere with areas of the brain usually associated with touch, participants are not only worse at reading braille, but also worse at feeling that their fingers are touching braille characters at all. Taken together this shows that the occipital lobes of these individuals have repurposed themselves in order to do a very complex thing (reading) using an unusual type of sensory information. 

Good job brain, you did it again!.. but how? And can we help?

Although we are still learning how exactly our brain manages to pull off this impressive feat of flexibility, scientists have two theories: 1) new connections being created between brain areas that supports sensation of touch and the occipital cortex⁶, and 2) existing connections between areas being strengthened⁶. 

Let’s imagine for a second that we could turn a science-fiction “dial” on the brain and make it more or less plastic whenever we wanted to. With such a dial, we potentially could help the brain learn faster and better. We could repurpose “jobless” brain areas from the loss of a sense like blindness or damage from a stroke ^5,7 (where the blood supply to the brain is interrupted or reduced, causing brain tissue damage), and turn them into productive parts of the brain once again. Not only could this help the brain learn, but increasing plasticity might also be used to help the brain forget⁸. This could be helpful for treating patients suffering from Post-Traumatic Stress Disorder where a traumatic event or memory is damaging their mental health, causing terrible distress ⁸. If we could help these patients forget these specific memories, we could effectively treat their condition and improve their quality of life substantially. 

Today, this “dial” is still science-fiction. However, every year it is becoming more and more attainable. With modern scientific advances identifying potential targets for plasticity promoting therapies ^7,8 we may soon be able to increase learning and bring care to many suffering individuals.

Change on the horizon

The brain is truly remarkable in its flexibility and resilience. From learning new skills to recovering from injury, the brain constantly finds ways to organize and reorganize itself depending on what is needed, and what is possible given the sensory information available to it.  As we continue to better understand the mysteries of brain plasticity, we will unlock potential therapies that could revolutionize how we treat neurological conditions. 

As a closing thought, there is something beautifully poetic about a brain (inside the head of a scientist/doctor) that is learning and adapting to better understand how it itself learns and adapts. With such remarkable plasticity, the future holds endless possibilities.

References 

1. Reh, R. K. et al. Critical period regulation across multiple timescales. Proceedings of the National Academy of Sciences 117, 23242–23251 (2020).
2. Cohen, L., Celnik, P., Pascual-Leone, A. et al. Functional relevance of cross-modal plasticity in blind humans. Nature 389, 180–183 (1997). 
3. Sadato, N., Pascual-Leone, A., Grafman, J. et al. Activation of the primary visual cortex by Braille reading in blind subjects. Nature 380, 526–528 (1996).
4. Hamilton, R. , Keenan, J. P. , Catala, M. & Pascual-Leone, A. (2000). Alexia for Braille following bilateral occipital stroke in an early blind woman. NeuroReport, 11 (2), 237-240.
5. Warraich Z, Kleim JA. Neural plasticity: the biological substrate for neurorehabilitation. PM R. 2010 Dec;2(12 Suppl 2):S208-19. doi: 10.1016/j.pmrj.2010.10.016. PMID: 21172683.
6. Merabet, L., Pascual-Leone, A. Neural reorganization following sensory loss: the opportunity of change. Nat Rev Neurosci 11, 44–52 (2010).
7. Su F, Xu W. Enhancing Brain Plasticity to Promote Stroke Recovery. Front Neurol. 2020 Oct 30;11:554089. doi: 10.3389/fneur.2020.554089. PMID: 33192987; PMCID: PMC7661553.
8. Lv T, Wang M, Zheng HS, Mao JD, Yang F, Yang L, Zhao MG, Liu SB, Zhang K, Liu R, Wu YM. Electroacupuncture alleviates PTSD-like behaviors by modulating hippocampal synaptic plasticity via Wnt/β-catenin signaling pathway. Brain Res Bull. 2023 Oct 1;202:110734. doi: 10.1016/j.brainresbull.2023.110734. Epub 2023 Aug 14. PMID: 37586426.

Cover Photo by Franco Antonio Giovanella on unsplash