Exploring the Resting State Neural Activity of Monolinguals and Late and Early Bilinguals

Exploring the Resting State Neural Activity of Monolinguals and Late and Early Bilinguals

ABSTRACT
Individuals who speak more than one language have been found to enjoy a number of benefits not directly associated with the use of the languages themselves. One of these benefits is that bilingual individuals appear to develop symptoms of dementia 4-5 years later than comparable individuals who speak just one language. Studies on this topic, however, do not necessarily account for factors including if the individual learned their second language as a child or later in life, or their language proficiency. In an attempt to more carefully examine these variables, this study looks at structural and resting-state functional MRI scans of the default mode network, English and Spanish (where applicable) proficiency, language background, and demographics of young healthy adults who fall into one of three groups: early bilinguals, late bilinguals, and monolinguals.

MRI METHODS

All imaging was performed on a 3T Siemens TIM Trio MRI scanner (Erlangen, Germany) using a 32-channel head coil at the BYU MRI Research Facility. Each participant contributed a structural MRI scan and a resting-state functional MRI scan. Structural scans used a T1-weighted MP-RAGE sequence with the following parameters: TR = 1900ms; TE = 2.26ms; acquisition matrix: 215 × 256; field of view = 218 × 250mm; slice thickness = 1.0mm; voxel size =.977 × .977 × 1.0mm; flip angle = 9°; and number of slices = 176; GRAPPA factor = 2. Resting state fMRI scans were performed using a T2*-weighted EPI sequence with the following parameters: TR = 875ms; TE = 43.6ms; slice thickness = 1.8mm; acquisition matrix = 100 × 100; flip angle = 55°; number of slices = 72; field of view = 180 × 180mm; voxel size = 1.8 × 1.8 × 1.8mm; multi-band factor = 8; volumes per run = 823 (total scan time = 12min). EPI scans were oriented parallel to the long axis of the hippocampus. All MRI scans were imported from DICOM to NIfTI file format using program dcm2nii (v. 1JUNE2015; http://www.nitrc.org/projects/mricron/). As part of the file conversion process, structural scans were reoriented to the nearest orthogonal using rigid-body transformation and extraneous field of view was cropped.