پردازش شنیداری جمله و پلنیوم‌گیجگاهی: شواهدی از تصویربرداری تشدید مغناطیسی عملکردی در دوزبانه‌ها

مقدمه: پژوهش حاضر با هدف بررسی نقش ناحیه پلنیوم ‌گیجگاهی چپ و راست در پردازش شنیداری جملات زبان اول و دوم در افراد دوزبانه اجرا شد. روش کار: جامعه آماری پژوهش حاضر، دانشجویان دوزبانه ترکی_فارسی شهر تهران در سال 1398 بود. داده ‌های 36 فرد دوزبانه که به روش هدفمند انتخاب شده بودند، در حین اجرای یک تکلیف شنیداری دوزبانه به روش تصویربرداری تشدید مغناطیسی کارکردی (fmri) اخذ شد. به منظور شناسایی الگوی فعالیت محرک ‌های دستوری_نادستوری زبان اول و دوم در ناحیه پلنیوم ‌گیجگاهی، آنالیزی بر مبنای ناحیه مطلوب (roi-based) در نرم‌ افزار fsl اجرا شد و درصد تغییر سیگنال به عنوان معیار «شدت» برای هر شرکت ‌کننده استخراج و در نرم ‌افزار spss نسخه 26 تجزیه و تحلیل آماری شد. یافته‌ ها: اگرچه معناداری اثر دستوری ‌بودگی برای هر دو زبان اول و دوم در پلنیوم ‌گیجگاهی چپ و راست مشاهده شد (0/001>p)، برانگیختگی پلنیوم‌ گیجگاهی چپ بیشتر بود. افزون بر این، پاسخ مغزی بزرگتر به جملات نادستوری زبان اول در مقایسه با جملات نادستوری زبان دوم در پلنیوم ‌گیجگاهی چپ محرز شد.نتیجه ‌گیری: هم‌ پوشانی همبسته ‌های نورونی دو زبان در پلنیوم ‌گیجگاهی، به عنوان یک واسط محاسباتی، سطح بالای بسندگی دوزبانه‌ های حاضر به زبان دومشان را که در سن 7 سالگی آموخته بودند، تایید می‌ کند. پلنیوم ‌گیجگاهی چپ نقش برجسته‌ تری در پردازش شنیداری جملات در افراد دوزبانه دارد که ممکن است دال بر یک سویه ‌شدگی این ناحیه باشد. فعالیت بیشتر زبان اول نسبت به زبان دوم در پلنیوم ‌گیجگاهی چپ، حاکی از این است که در حالت دوزبانه و در شرایطی که فرد دوزبانه به هر دو زبان اول و دوم خود به یک میزان مسلط است، زبان اول به عنوان زبان پایه عمل می ‌کند که مستلزم صرف زمان و منابع شناختی بیشتر برای مهار و فعال ‌سازی مجدد این زبان است.  

the auditory sentence processing and the planum temporale: evidence from functional magnetic resonance mapping in bilinguals

introductionto our knowledge, no study has yet used the auditory paradigm to investigate pt activation during l1-l2 sentence processing. employing this experimental design is critical to our understanding of target/non-target language activation. moreover, research in this area has mainly been limited to the neuroanatomical or pathological studies with little attention to bilinguals. consequently, the extent to which the bilateral pts are activated during simultaneous l1-l2 processing needs to be clarified. the present study aims to explore these critical issues.to address this study’s goal, the discussion critical revolve around the following questions:q1. do the left and right pt act differently for the auditory sentence processing?q2. are l1 and l2 processed differently in the pl?methodsthis study recruited healthy and young bilingual adults through social media via advertisements on top universities in tehran, iran. in total, forty-one subjects participated in the experiment. five subjects were excluded due to technical problems. the final sample consisted of thirty-six (21 female, all right-handed). all participants were native speakers of turkish who had learned persian as l2 at the age of seven when entering school. participants underwent an fmri scan and completed an auditory grammaticality judgment task in the scanner. during the 21.5-min fmri scan, participants were required to judge each sentence for grammatical correctness by pressing the button of a left (ungrammatical) or right (grammatical) response grip with the thumb while minimizing head movements. the task included four alternating rest and auditory sentence blocks. each auditory sentence block had 32 runs and was bookended by 30-second rest periods where no stimuli were presented, allowing for hemodynamic baseline data collection. correct and violated sentences were randomly intermixed within each block, but language blocks alternated in a fixed sequence. in total, 128 spoken sentences (50% in l1 and 50% in l2, with 50% violation per language) were used to assess syntactic processing in bilinguals. images were acquired with a siemens prisma 3-tesla scanner at nbml. the fmri images were collected using an echo-planar imaging (epi) sequence with a 20-channel head coil consisting of 430 volumes and 45 axial slices per volume (repetition time (tr)=3000 ms, echo time (te)=30 ms, flip angle=90◦, matrix size=64×64, slice thickness=3 mm, field of view (fov)=192 mm2, voxel size=3×3×3 mm3). moreover, the high-resolution t1-weighted structural images were collected through a magnetization-prepared rapid gradient-echo (mprage) sequence (tr=1800 ms, te=3.53 ms, flip angle=7◦, matrix size=256×256, slice thickness=1 mm, fov=256 mm2, voxel size=1×1×1 mm3, duration=5-min). the anatomical mprage volumes were pre-processed following the brain extraction and used as anatomical references in the functional image processing co-registration steps using feat in fsl. the fmri analyses were performed according to a standard pipeline comprising the following steps: motion correction and realignment, slice-timing correction, segmentation and normalization to the standard mni template and spatial smoothing (6 mm full-width at half-maximum isotropic gaussian), temporal filtering (with sigma=50.0 s), and exploratory ica-based data analysis. the general linear model (glm) was used to construct the statistical model on the bold response to perform the first-level analysis. z (gaussianised t/f) statistic images were thresholded using clusters determined by z>3.1 and a (corrected) cluster significance threshold of p<0.05. a whole-brain analysis was performed to detect the mechanisms underlying syntactic processing in the bilateral pt. then, psc was extracted as an intensity measure in this region per participant according to the harvard-oxford atlas implemented in fsl. all statistical analyses were conducted in ibm spss statistics v26.resultswhole-brain results of brain activationfigure 1a visualizes the location of the pt. figure 1b exhibits the patterns of whole-brain activation during the presentation of corrected and violated stimuli in l1 and l2 for each hemisphere. greater left-hemispheric activation is detectable for the region of the pt (white circles) when comparing the left and right columns.roi-based resultsthe results are depicted in figure 2. the main factor of grammaticality yielded a significant effect (f (1, 35)=53.296, p<0.001, ƞp2 =0.618), with a more significant effect for grammatical (3.712 psc) as compared to ungrammatical stimuli (3.303 psc). furthermore, a significant main effect of the hemisphere (f (1, 35)=25.451, p<0.001, ƞp2 =0.435), indicating that the left hemisphere (4.014) generated stronger psc as compared to the right hemisphere (3.000). a significant grammaticality×hemisphere interaction (f (1, 35)=16.449, p=0.001, ƞp2 =0.333) indicated that the left hemisphere triggered a more significant effect for l1 stimuli (4.113) than for l2 stimuli (3.916) (t (35)=3.517, p=0.001), whereas in the right hemisphere there were no differences between l1 (2.970) and l2 (3.030) sentences (t (35)=-1.176, p=0.248).  finally, the grammaticality×language×hemisphere interaction (f (1, 35)=7.961, p=0.008, ƞp2 =0.194) turned out to be significant. the analysis by the grammaticality factor showed that in the left hemisphere, l1-grammatical stimuli (4.244) engendered a larger effect than l1-ungrammatical stimuli (3.866) (t (35)=2.980, p=0.005). similarly, l2-grammatical stimuli (4.161) engendered a larger effect than l2-ungrammatical stimuli (3.672) (t (35)=5.311, p<0.001). in the right hemisphere, l1-grammatical stimuli (3.204) engendered a larger effect than l1-ungrammatical stimuli (2.737) (t (35)=5.363, p<0.001). similarly, l2-grammatical stimuli (3.214) engendered a larger effect