The act of speaking a language comes from recalled experiences with the words, syntax, intonations, and pronunciations. Someone learning a new language will mistakenly use the syntax, intonations, and pronunciations of his or her native language when speaking the new language. The result is what we refer to as an “accent.”
There are cases of people suddenly speaking with a pronounced foreign accent, illustrating that all experiences are accessible, including the language-speaking repertoire of someone who speaks with a recognizable accent. The phenomenon is called “foreign accent syndrome,” or “dysprosody.”
One study identified and studied 62 subjects experiencing spontaneous foreign accent syndrome.[i] The same authors in another study found 112 cases of dysprosody in their meta-analysis of studies.[ii] These subjects were suddenly accessing a different repertoire of language experiences because all experiences are accessible, including the experiences of vocalizing a language with the accent of a nonnative speaker.
[i] Peter Mariën, Jo Verhoeven, Peggy Wackenier, S. Engelborghs, and P. De Deyn, “Foreign accent syndrome as a developmental motor speech disorder,” Cortex, 45 (7) (2009): 870–878.
[ii] Peter Mariën, Stefanie Keulen, and Jo Verhoeven, “Neurological Aspects of Foreign Accent Syndrome in Stroke Patients,” Journal of Communication Disorders, 77 (January 2019): 94–113.
You can see accounts of foreign accent syndrome in the videos that follow.