Filippopolitis, K; (2006) Language recovery in Greek-English bilingual stroke patients: An fMRI study. Doctoral thesis , UCL (University College London).

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Abstract

As bilingualism has become more and more common, we were initially interested in how stroke impacted upon language abilities in bilingual participants. For practical reasons, the languages chosen were Greek and English. Due to unavailability of suitable patients, however, we used our experimental paradigm to answer two specific questions: (1) How does a Greek patient recover reading ability in their own language despite damage in or near the normal reading system (2) Do neurologically normal bilinguals show the same or different activation patterns when reading in Greek or English First, an overview of the major questions and the most widely accepted answers about bilingualism is presented as background. I then describe how functional imaging can be used to complement the classic psycholinguistic approach. Our results confirm, once again, the widely accepted notion that different languages are served by the same gross set of neuroanatomical regions in the healthy brain. The absence of significant differences between Greek and English also confirm that our subjects were highly proficient in both languages. Our patient data showed abnormal activation patterns in patients who were performing the reading task well. Patient TE, with a left parietal lesion, had the most interesting results. As expected TE showed less activation than the neurologically normal controls at the site of his lesion. In addition, he also showed less activation than normal in bilateral premotor and superior temporal regions that are associated with speech output. These areas looked structurally normal on TE's MRI. Reduced activation in the context of recovered speech output suggest that, pre-stroke, these areas relied on excitatory input from the left parietal region that was now damaged. In other words, the damaged parietal cortex and the undamaged premotor and superior temporal regions are likely to interact during normal speech output. In contrast, TE showed enhanced activation in the left frontal lobe and right cerebellum. We interpret this activation as a result of the use of a non- typical cognitive strategy in order to cope with the speech output task when the normal system is damaged. The clinical implications of our findings are also discussed.

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