The brain’s ability to use and comprehend language grows significantly during early childhood as infants begin interpreting the words they hear and constructing their own sentences. Language-processing areas in the brain continue to develop in older children, allowing them to expand their vocabulary and use language more adaptively. MIT researchers have captured images of the language-processing network’s development in brain scans from hundreds of children and teenagers. Their findings, published on May 16 in Nature Communications, indicate that this network matures and becomes more integrated and responsive until about age 16. Crucially, they found that the adult language network’s localization in the left brain is established early.<\/p>\n
It is commonly recognized that language use predominantly involves the left hemisphere. Adults rely on left-brain language-processing regions when reading, writing, speaking, or listening. There was uncertainty about whether this lateralization is present early in life or develops as the language network matures, with both brain hemispheres contributing during childhood. To investigate, MIT researchers, including Evelina Fedorenko, John Gabrieli, and Rebecca Saxe, shared brain scans from children, adolescents, and adults to compare language response. These researchers, part of the McGovern Institute for Brain Research, used functional MRI data from “language localizer” tasks to map each individual’s language-processing network.<\/p>\n
In their studies on cognitive functions and developmental disorders, the research teams collected functional MRI data while subjects performed language and non-linguistic tasks. This helped identify brain areas dedicated to language processing, which vary anatomically among individuals. Children were asked to listen to stories in an MRI scanner, with the material varying by age. The researchers also observed brain activity during non-linguistic tasks by having children listen to nonsense words. Data from ages 4 to 16, plus adult comparisons, revealed developmental changes in brain response to language. Ola Ozernov-Palchik noted stronger system integration and activation in older children, reflecting improved comprehension.<\/p>\n
Interestingly, language processing was primarily on the left side of the brain, even in the youngest participants. “From age 4 on, it seems just as lateralized as in an adult,” stated Gabrieli. This finding impacts our understanding of developmental disorders affecting language, such as autism and dyslexia, where the right brain often plays a larger role. “Almost every single developmental disorder associated with language has a theory related to language lateralization,” explained Ozernov-Palchik. The team aims to learn more about brain areas involved in language processing in children under 4 and during infancy to better understand brain development and developmental disorders.<\/p>\n
Previously, scientists believed that gradual lateralization development explained why left hemisphere damage affects language differently depending on the timing. “If you have damage to the left hemisphere as an adult, you\u2019re very likely to end up with some form of aphasia, at least temporarily,” Fedorenko noted. In contrast, early left hemisphere damage often doesn’t prevent language development, possibly due to early right hemisphere involvement. However, recent findings suggest the brain’s early plasticity allows for strong lateralized responses by age 4, indicating the developing brain’s adaptability.<\/p>\n