The ability to learn new words may depend on the strength of the connection between the areas of the brain involved in auditory processing and articulation, researchers reported in the journal PNAS recently.
Scientists have long hypothesized that hearing and repeating unfamiliar words is the key to learning them. A 2011 experiment, for example, found that subjects had a hard time picking up new words if they simultaneously made irrelevant sounds while trying to memorize the vocabulary items. The current study, by researchers from King’s College London Institute of Psychiatry and the University of Barcelona, traces that phenomenon to a part of the brain known as the arcuate fasciculus, a neural network in he left hemisphere that runs between the regions responsible for language interpretation and speech production.
Using MRI scans and a brain mapping technique called diffusion tensor imaging, the researchers examined the structure and function of the brains of 21 healthy volunteers in their mid 20s. Nine of the participants were female and 11 were male; all spoke Spanish as their primary language.
First, the researchers instructed participants to memorize nine made-up three-syllable words, which were presented in random order in a pattern similar to real language. The participants later tried to recall if they had heard the words or not. While they performed these tasks, the researchers monitored their brain activity with the MRI machine.
Participants who learned the new words quickly had more myelination – the fatty coating around the nerve cells that speeds up signaling in the brain. The activity between the auditory and motor regions of the brain was also more coordinated in these participants.
While apes and monkeys have brain regions similar to the ones responsible for auditory and motor processing of language in humans, the arcuate fasciculus in apes and monkeys is structurally different, and the connection between those regions is not as strong. In humans, the arcuate fasciculus continues to develop through childhood, until about seven years old, and there is evidence that it is also important in early language acquisition.