Bilingual brain interhemispheric interactions

2023 Imminent Research Grants Winning project – Neuroscience of Language Category

Have you ever wondered how people who speak two languages manage to switch between them so easily? Scientists are exploring this fascinating ability, and they’re discovering some interesting things about how our brains handle multiple languages.

The Challenge of Being Bilingual

When bilingual people prepare to speak, both of their languages become active in their mind at the same time. This can cause a bit of a mental traffic jam, with words from both languages competing for attention. To speak clearly, bilinguals need to push aside the words from the language they’re not using at the moment. A part of the brain called the dorsolateral prefrontal cortex (dlPFC for short) plays a big role in this process. Think of it as a traffic controller for your thoughts. This brain area is important for executive functions, including response inhibition, interference control, and cognitive flexibility.

Two Sides Working Together

Our brains have two halves, or hemispheres, and scientists are curious about how these two sides work together when we use language. Previous research has found that the connections between the left and right sides of the brain are really important for processing a second language efficiently. Interestingly, people who are bilingual seem to have stronger connections between the two sides of their brain. This improved brain communication might help them switch between languages more easily.

A Special Group: Simultaneous Interpreters

Most studies have looked at regular bilingual people, but there’s a group that’s especially interesting: professional simultaneous interpreters. These are the amazing folks who can listen to someone speak in one language and immediately translate it into another language. We think their exceptional skills might give us special insights into how the bilingual brain adapts to become really good at handling two languages.

New Ways to Study the Brain

Our research group is using some cutting-edge tools to study how the bilingual brain works. One is Transcranial Magnetic Stimulation (TMS), a technique that uses magnetic fields to safely stimulate specific parts of the brain, allowing us to probe neural functions with precision. The other is electroencephalography (EEG), a method to record the brain’s electrical activity using sensors on the scalp, allowing to observe neural processes in real-time. Combining these methods enables us to not only observe brain behavior but also carefully modulate its activity, providing deeper insights into cause-and-effect relationships within the bilingual brain.

Our Study

We’re now using these techniques to study how the left and right dlPFC work together in bilingual people, especially in expert simultaneous interpreters. We’re utilizing cortico-cortical paired associative stimulation (ccPAS), a TMS technique that enhances connectivity between two cortical areas. Our preliminary data from non-expert bilinguals reveals fascinating patterns: 1) Enhancing left-to-right dlPFC connectivity leads to improved inhibitory control, as measured by a Go-NoGo task; 2) Enhancing right-to-left dlPFC connectivity results in reduced risk-taking behavior in the Balloon Analog Risk Task; 3) These behavioral improvements correlate with modulations in brain activity, particularly in frontal alpha asymmetry, suggesting larger resource allocation to the left hemisphere, central in language processing.

Why This Matters

Our preliminary findings in non-expert bilinguals suggest that the balance and communication between the left and right dlPFC may play a crucial role in optimizing executive functions, which in turn, are essential for switching between languages. We believe this research could help us understand how the bilingual brain works and potentially lead to new ways to improve language learning and processing. By studying the brain’s “wiring” for language, we might find ways to help people become more proficient in multiple languages or even recover language skills after brain injuries. In the future, we might even see TMS-based techniques that could enhance bilingual language processing by strengthening the connections between the two sides of the brain.

Conclusion

As scientists, we’re continually amazed by the human brain’s ability to handle multiple languages. As we continue to unravel the mysteries of the bilingual brain, we’re gaining valuable insights into the incredible flexibility and adaptability of our minds. Our research not only satisfies our curiosity about how we think and communicate but could also lead to practical applications in education, therapy, and beyond. We’re excited to continue this work and share our findings with you.

Team Members

Assistant Professor in Cognitive Neuroscience at Alma Mater Studiorum – University of Bologna

Full Professor in Cognitive Neuroscience at Alma Mater Studiorum – University of Bologna

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