Image credit: Public domain (CC0)
Our brains are dynamic organs that respond to, and are shaped by, our life experiences. Sometimes, this even results in alterations in the shape and size of their various regions.
The auditory cortex is one of the brain areas processing speech. In people who have mastered more than one tongue, it is also tasked with recognising and distinguishing between speech sounds from different languages.
Although previous research suggests that being bilingual can influence brain anatomy, these changes are still poorly understood. How different parts of the auditory cortex are structured, or how they work together has also remained unclear. Kepinska et al. therefore set out to determine if the structure of the brain's auditory cortex is shaped by language experience. To do so, they used an imaging technique known as structural MRI to take detailed pictures of the auditory cortex of over 200 people who each spoke between one and seven languages. In total, 36 different languages were represented across the entire group.
The scans showed that a specific part of the auditory cortex, called the second TTG, was thinner in people who spoke more languages. Further analysis revealed that some of this variation in TTG thickness was associated with the variety of speech sounds present in the languages that participants were familiar with: the more languages someone spoke, and the greater the sound differences between them, the thinner the second TTG. These results suggest that the auditory cortex is shaped by a process called ‘experience-driven efficiency’; in other words, the TTG needs less tissue to do its job in people who have more experience in different languages.
Going forward, Kepinska et al. hope that these findings may help refine our understanding of how the brain adapts to language exposure. This, in turn, could improve both educational interventions and clinical therapies, for example to help people with dyslexia or hearing impairments.
