White matter differences between bilinguals and monolinguals revealed by diffusion tensor imaging (DTI)

Seyede Ghazal Mohades, Esli Struys, Robert Luypaert

Research output: Contribution to journalConference paper

Abstract

Introduction
The two main areas in the human brain associated with language are Broca's and Wernicke's areas. Broca's area (BA) is responsible for speech production, language processing, language comprehension, as well as controlling facial neurons (language outputs). Wernicke's area (WA) is thought to be the language receptive center, which processes the words that we hear or read (language input). A large bundle of neurons, called Arcuate Fasciculus, connects these two areas. White matter pathology and morphology can be investigated by means of DT-MRI based fiber tracking. Previous study has shown significant differences between bilinguals and monolinguals in the ratio of the anterior midbody (AMB) and the total corpus callosum (CC) midsagittal areas [see Figure 1 Left]. The AMB is dedicated to primary motor and somatosensory interconnections.
Aim
The hypothesis of our study was that the regions associated with language exhibit structural differences in bilinguals and monolinguals and that MRI DTI can be used to assess these differences. Our specific goal was to demonstrate differences in the white matter fibers connecting BA to WA, fibers going from BA to CC and also from AMB to the primary motor cortex.
Materials and Methods
The experiments were conducted on a 3T MR system (Philips Achieva Release 2.5), with an 8 channel SENSE head coil. Two groups, respectively containing 6 monolingual and 7 bilingual children (right-handed, healthy males and females, 8-11 year old), were scanned. A single-shot spin-echo, echo-planar sequence (SS-SEEPI) with 15 non-collinear diffusion gradient directions and b= 700 s/mm2 was used.
Other imaging parameters were: TR/TE=6484ms/ 60ms, FOV=224x224x120 mm3, 60 oblique axial 2mm slices, total scan duration=454s. Mean fractional anisotropy (FA) in selected bundles of neurons was calculated for each subject using DTIstudio software (Johns Hopkins University, Baltimore, USA). The bundles were obtained by tracing three sets of fibers [see Figure 1]: from the white matter region underlying BA to WA (shown in red); from CC to BA (shown in green) and from AMB to the primary motor cortex (shown in yellow).
Independent samples t-tests were performed to compare the mean FA values between groups. A P-value of less than 0.05 was considered significant.
Results and Discussion
Table 1 shows that the mean FA values of the fibers connecting BA to WA is higher in bilinguals, whereas the fibers going from BA to CC have higher mean FA value in monolinguals. No significant difference could be found between the FA values of the fibers connecting AMB and primary motor cortex.
These results support the hypothesis that bilingual and monolingual brains are different. The study demonstrates that DTI can help understanding structural differences between the white matter of bilingual and monolingual brains.
Original languageEnglish
Pages (from-to)2316-2316
Number of pages1
JournalProc. Intl. Soc. Mag. Reson. Med.
Volume19
Issue number19th Annual Meeting
Publication statusPublished - 7 May 2011
EventUnknown -
Duration: 7 May 2011 → …

Keywords

  • DTI
  • bilingualism
  • MRI

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