Scientists reveal new insights into brain function in congenital deafness

^{Translation: Diana Taborda}

A research team led by the University of Coimbra (UC) has provided new information aimed at understanding the plasticity of the brain in individuals with congenital deafness (present from birth). The scientists were able to unveil how the auditory cortex − typically responsible for processing auditory information in normal-hearing individuals − processes visual information in people with congenital deafness.

These findings offer valuable insights into the design and optimisation of cochlear implants (an electronic device that stimulates the auditory nerve) and other medical prostheses that could improve the quality of life for people with hearing impairments.

Research has shown over the years the remarkable ability of the human brain to adapt to congenital sensory deprivation, such as blindness or deafness, a phenomenon known as neuroplasticity. This study shows that there are substantial neuroplastic changes in the auditory and visual networks caused by deafness, and highlights how sensory systems dynamically adapt to congenital hearing loss.

In the study, 31 individuals were divided into two groups: 15 with congenital deafness and 16 with normal hearing, who were exposed to various visual stimuli during an MRI scan. “We are aware that individuals deprived of one sense experience changes in the organization and structure of the brain. In such cases, areas of the brain where information transmission is absent take on alternative functions. This contrasts with individuals whose sensory areas are fully operational, where such adaptive changes are not observed. We also know that in congenitally deaf people, the auditory cortex of deaf individuals is activated following visual stimuli. So, our goal was to understand how visual information reaches the auditory cortex of congenitally deaf individuals,” explains Zohar Tal, a researcher at the Faculty of Psychology and Educational Sciences of the University of Coimbra (FPCEUC).

The research team concluded that in congenitally deaf individuals, the visual information processed in the auditory cortex originates from subcortical structures such as the thalamus, lateral geniculate body, or pulvinar. “These are brain structures typically associated with visual processing, which, in normal hearing individuals, send information to the visual cortex”, explains the principal investigator (PI) Jorge Almeida, FPCEUC professor and researcher. He further adds that “These structures process simpler sensory and visual information and are a key part of initial visual processing.”

The scientific article titled 'Neuroplastic Changes in Functional Wiring in Sensory Cortices of the Congenitally Deaf: A Network Analysis' involved scientists from universities in Germany, China, and the United States of America. It has been published in the journal Human Brain Mapping and is available at https://doi.org/10.1002/hbm.26530.