Close your eyes and listen. Listen to the noises you hear, the scents that you smell, and the feeling of skin surfacing your body. Why is it that we only notice this once our eyes are closed? This is the concept behind neuroplasticity. Neuroplasticity is the ability for the brain to reorganize itself by creating new synaptic connections (Torday, 2015). The body attempts to maintain homeostasis through feedback systems, systems that allow self-regulation and internal balance. Neuroplasticity exemplifies the behaviour of a positive feedback system as it adapts to changes occurring in the brain. Individuals who suffer from blindness are a prime example of how the brain uses neuroplasticity to counteract impairment in one of the senses.
Those visually impaired frequently demonstrate heightened proficiency in their functioning senses when compared to sighted people. Regions of the brain that are deprived of targeted sensory inputs may undergo the readjustment of resource processing to other sensory modalities (Mašić et al., 2020). Sensory specific areas like the visual cortex, receive direct and prompt inputs from other stimulus systems in the body. The National Library of Health (Billman, 2020) explored a phenomenon where the visual cortex activates when learning braille (Figure 1). In the case of children with congenital blindness, the visual cortex undergoes redistribution at an early age in order to accommodate the depletion of sight.
Figure 1: The figure expressed above exemplifies the English alphabet and their translations to braille. In the braille alphabet, specific patterns are followed. Braille consists of raised dots arranged in a grid of six dots, organized into two columns of three dots each. Different combinations of raised dots within this grid represent letters, numbers, and other symbols (Canada Science and Technology Museum, 2024).
A cohort composed of 12 subjects with early onset blindness (either congenital or acquired before the age of three) was contrasted with a control group of 16 individuals, all possessing typical visual acuity within the same age bracket (Billman, 2020). The neuroimaging scans of the premature blindness cohort revealed clear disruptions in both structural and functional brain connectivity (Mašić et al., 2020). Notably, augmented connections in certain regions of the brain were also observed. This was concluded to facilitate bi-directional information exchange in the readjustment of resource processing stated above. This phenomenon was not observed in the control group. The learning of braille can be connected to this clear bi-directional information exchange.
Typically, the visual pathway begins with the eye, where light signals from the surrounding areas are converted into neuron impulses in the retina. This visual information then travels through the optic nerve, optic chiasm, and then the optic tract to reach the thalamus (specifically two lateral geniculate nuclei). The lateral geniculate nuclei that make up the thalamus act as the control centre for processing information, sorting it into three areas of the brain: the primary visual cortex, the superior colliculi, and the pretectal area (Mašić et al., 2020). In order to study how the brain adapts this natural process to learn to read through touch, it is crucial to comprehend the structure and function of the visual and parietal lobes. These lobes are vital for the reading of braille. Understanding the anatomy and neurology of these brain regions is key to unraveling the intricacies of brain plasticity and tactile braille reading.
When a blind individual reads braille, the visual cortex aids in touch processing. Unlike sighted people who utilize the visual cortex in order recognize letters, those who are blind utilize the sense of touch. This ability to modify another sense in order to fill the role of a non-existing one shows how remarkable the the brain is.
Work Cited
Billman, G.E., 2020. Homeostasis: The Underappreciated and Far Too Often Ignored Central Organizing Principle of Physiology. Frontiers in Physiology, 11, p.200. https://doi.org/10.3389/fphys.2020.00200.
Canada Science and Technology Museum, 2024. Braille. [online] Available at: <https://ingeniumcanada.org/scitech/education/try-this-out/braille> [Accessed 9 November 2023].
Mašić, V., Šečić, A., Trošt Bobić, T. and Femec, L., 2020. Neuroplasticity and Braille reading. Acta Clinica Croatica, 59(1), pp.147–153. https://doi.org/10.20471/acc.2020.59.01.18.
Torday, J.S., 2015. Homeostasis as the Mechanism of Evolution. Biology, 4(3), pp.573–590. https://doi.org/10.3390/biology4030573.