Screen Readers Skip to Content
🖶 Print page

Why Congenitally Blind Show Activity in Brain Visual-Processing Areas

Published: 2023-01-20
Author: D'Or Institute of Research and Education (IDOR) | Contact: en.idor.org
Peer-Reviewed Publication: Yes
Additional References: The Human Brain Publications

Synopsis: Often people born blind can activate the vision-processing region of the brain, the occipital cortex, when engaging in a non-visual activity, such as reading in Braille. Brain plasticity, which is the brain's ability to reorganize its connections to face adversity. This process can involve a series of structural modifications, such as developing new neural pathways or reorganizing existing connections. The study described in humans an alternative mapping in the connectivity of the thalamus with the occipital and temporal cortices, and these plastic reorganizations may be a mechanism capable of explaining how non-visual stimuli reach and activate the visual cortex in congenitally blind people.

advertisements

Definition

Congenital Blindness

Congenital blindness refers to diseases and conditions occurring in childhood or early adolescence of those below 16 years old. If left untreated, it results in blindness or a severe visual impairment, likely to be permanent blindness later in life. Various causes can promote congenital blindness, but the most concerning and highest reason is a genetic mutation. In general, 60% of congenital blindness cases are from the prenatal stage, and 40% are from inherited diseases. Most congenital blindness cases show that early treatment can be avoidable or preventable.

Main Digest

Reorganization of Thalamocortical Connections in Congenitally Blind Humans - Human Brain Mapping

New study unravels the brain structural reorganization of those born sightless. Recently published in the scientific journal Human Brain Mapping, a Brazilian study has identified for the first time the reorganization of anatomical structures in the brain of people with congenital blindness. The research was carried out by the D'Or Institute of Research and Education (IDOR), the Federal University of Rio de Janeiro (UFRJ), and the Center for Specialized Ophthalmology, Brazil.

Related Publications:

A few decades ago, scientific studies reported the curious discovery that people born blind could activate the vision-processing region of the brain, the occipital cortex, when engaging in a non-visual activity, such as reading in Braille (a tactile language system). These studies were further evidence of the so-called brain plasticity, which is the brain's ability to reorganize its connections to face adversity. This process can involve a series of structural modifications, such as developing new neural pathways or reorganizing existing connections.

"Soon after we are born, we are exposed to stimuli captured by our senses, which are fundamental to determine the brain's circuitry. It is also a time in which our brain is in great transformation. Technically we could think that the occipital cortex would be functionless in people who were born blind, but we know that this is not the case. It is activated. What we lacked to understand was the structural process behind it," explains Dr. Fernanda Tovar-Moll, corresponding author of the current study and president of IDOR.

In the research, magnetic resonance imaging techniques were used to analyze structural connectivity in the human brain and to investigate the possibility of alternative neural connections. The neural images of 10 individuals with congenital blindness and Braille readers were compared to a control group of 10 individuals with intact vision. After detailed analysis, the scientists observed structural changes of connectivity in the thalamus, a structure located in the diencephalon, the central region of the brain that receives, processes, and distributes information captured by the main human senses - such as vision, hearing, and touch - to the different brain regions.

The yellow box (left) depicts thalamic areas that exhibited increased connectivity with the temporal cortex, including MGN, LGN and pulvinar bilaterally. The blue box (right) represents thalamic territory that displayed decreased connectivity with the occipital cortex in congenitally blind individuals, namely the left pulvinar/lateral posterior nucleus. The white box (middle) shows thalamic territories obtained from an atlas based on the Colin 27 Average Brain 58. It depicts the location of LGN (green), MGN (dark pink), pulvinar (red), medial dorsal (yellow), ventral anterior (orange), anterior (purple), and lateral posterior (light pink) nuclei. A graphical overlay (dark blue) of thalamic areas that exhibited both increased connectivity to the temporal cortex and decreased connectivity to the occipital cortex (p<0.05, FWE-corrected) in CB individuals is shown (white box, bottom). L = left; R = right; A = anterior; P = posterior. The coordinates are given according to the MNI space and plotted on the MNI standard brain. Color bars represent the t-value - Image Credit: D'Or Institute for Research and Education(IDOR).
The yellow box (left) depicts thalamic areas that exhibited increased connectivity with the temporal cortex, including MGN, LGN and pulvinar bilaterally. The blue box (right) represents thalamic territory that displayed decreased connectivity with the occipital cortex in congenitally blind individuals, namely the left pulvinar/lateral posterior nucleus. The white box (middle) shows thalamic territories obtained from an atlas based on the Colin 27 Average Brain 58. It depicts the location of LGN (green), MGN (dark pink), pulvinar (red), medial dorsal (yellow), ventral anterior (orange), anterior (purple), and lateral posterior (light pink) nuclei. A graphical overlay (dark blue) of thalamic areas that exhibited both increased connectivity to the temporal cortex and decreased connectivity to the occipital cortex (p<0.05, FWE-corrected) in CB individuals is shown (white box, bottom). L = left; R = right; A = anterior; P = posterior. The coordinates are given according to the MNI space and plotted on the MNI standard brain. Color bars represent the t-value - Image Credit: D'Or Institute for Research and Education(IDOR).

"Plasticity has been the research focus of our group for many years now, and in this case of cross-modal plasticity in congenitally blind people, in which distant areas of the brain present this communication, we suspected that the phenomenon would be originating in the thalamus, as it is the brain structure responsible for connecting several cortical regions, and it could be an area that with little change in the axonal circuitry [part of the neuron responsible for conducting electrical impulses] would be able to connect cortices that were distant from one another", comments the neuroscientist.

The research also observed that the area of the thalamus dedicated to connecting with the occipital cortex (vision) was smaller and weaker in blind individuals, giving space to connections with the temporal cortex (hearing), which were shown to be strengthened when compared to those observed in individuals without visual impairment. This means that in addition to being activated, the visual cortex is also invaded by connections that refine other senses, such as hearing and touch.

It was the first time that a study described in humans an alternative mapping in the connectivity of the thalamus with the occipital and temporal cortices, and these plastic reorganizations may be a mechanism capable of explaining how non-visual stimuli reach and activate the visual cortex in congenitally blind people.

"Neuroimaging studies allow us to navigate the structure of the brain and better understand the diversity of brain plasticity, which can also pave the way for discoveries such as new visual rehabilitation initiatives", adds Dr. Tovar-Moll, informing that her research group is still involved in other studies with congenitally blind people in which they investigate, in addition to the structure, the functional adaptations of brain plasticity in this population.

Reference Source(s):

Why Congenitally Blind Show Activity in Brain Visual-Processing Areas | D'Or Institute of Research and Education (IDOR) (en.idor.org). Disabled World makes no warranties or representations in connection therewith. Content may have been edited for style, clarity or length.

Post to Twitter Add to Facebook
advertisements

Disabled World is an independent disability community established in 2004 to provide disability news and information to people with disabilities, seniors, their family and/or carers. See our homepage for informative news, reviews, sports, stories and how-tos. You can also connect with us on Twitter and Facebook or learn more about Disabled World on our about us page.

Disabled World provides general information only. The materials presented are never meant to substitute for professional medical care by a qualified practitioner, nor should they be construed as such. Financial support is derived from advertisements or referral programs, where indicated. Any 3rd party offering or advertising does not constitute an endorsement.


Cite This Page (APA): D'Or Institute of Research and Education (IDOR). (2023, January 20). Why Congenitally Blind Show Activity in Brain Visual-Processing Areas. Disabled World. Retrieved January 27, 2023 from www.disabled-world.com/health/neurology/brain/congenitally-blind.php

Permalink: <a href="https://www.disabled-world.com/health/neurology/brain/congenitally-blind.php">Why Congenitally Blind Show Activity in Brain Visual-Processing Areas</a>