When presented with English words containing either of these sounds, brain imaging studies show that only a single region of a Japanese speaker’s brain is activated, whereas in English speakers, two different areas of activation show up, one for each unique sound.For Japanese speakers, learning to hear and produce the differences between the two phonemes in English requires a rewiring of certain elements of the brain’s circuitry. What can be done? How can we learn these distinctions?
Source: What happens in the brain when you learn a language? | Education | The Guardian