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Title:	Kajian fMRI ke atas pengkhususan kefungsian dan kehubungan efektif otak di kalangan subjek hilang pendengaran unilateral
Authors:	Mazlyfarina Mohamad (P36719)
Supervisor:	Ahmad Nazlim Yusoff, Prof. Madya. Dr.
Keywords:	Hilang pendengaran unilateral Ketakupayaan Universiti Kebangsaan Malaysia -- Dissertations Dissertations, Academic -- Malaysia
Issue Date:	8-Oct-2012
Description:	Komunikasi lisan selalunya berlaku dengan kehadiran hingar latar belakang menyebabkan kesukaran bagi seseorang untuk memahami apa yang disampaikan terutama oleh mereka yang mempunyai masalah pendengaran unilateral. Ini kerana proses ini melibatkan bukan hanya kawasan auditori, tetapi juga kawasan kognitif dalam otak. Kajian terdahulu menunjukkan wujudnya pengorganisasian semula korteks untuk memampas ketakupayaan akibat hilang pendengaran unilateral. Walau bagaimanapun, tidak banyak diketahui mengenai interaksi kefungsian dalam pusat pemprosesan persepsi pertuturan dan ingatan bekerja. Tambahan pula, pengaruh bahagian telinga yang hilang pendengaran serta hingar latarbelakang ke atas pengorganisasian semula korteks masih tidak jelas. Oleh itu, kajian ini dijalankan untuk menentukan pengorganisasian semula korteks dalam aspek pengkhususan kefungsian dan hubungan efektif ke atas tugasan persepsi pertuturan (SP) dan ingatan bekerja (WM) dalam senyap dan hingar. Dalam kajian ini, imbasan pengimejan resonans magnet kefungsian (fMRI) dilakukan ke atas subjek i) berpendengaran normal pada kedua belah telinga (NH, n = 14), ii) hilang pendengaran unilateral kanan (RHL, n = 6) dan iii) hilang pendengaran unilateral kiri (LHL, n = 6). Setiap subjek melakukan tugasan SP dan WM dalam imbasan berasingan dalam mana subjek diperdengarkan secara binaural satu siri lima perkataan secara bergilir-gilir dalam senyap (WIS) dan dengan kehadiran hingar latar belakang (WIN). Pemetaan statistik berparameter (SPM8) dan pemodelan dinamik penyebab (DCM10) digunakan untuk menentukan sifat pengkhususan kefungsian dan kehubungan efektif otak. Untuk setiap subjek, sejumlah 66 model kehubungan efektif bagi SP dan 72 bagi WM dibina untuk setiap hemisfera bagi menguji kewujudan gandingan di antara korteks singulat anterior (ACG), korteks auditori primer (PAC), girus temporal superior (STG) dan girus frontal inferior (IFG) dengan tambahan kawasan lobus parietal inferior (IPL) bagi WM. Keputusan pengkhususan kefungsian menunjukkan pengaktifan bilateral pada lobus auditori, frontal dan parietal pada aras keertiaan tak diperbetulkan (p<0.001) ke atas untuk semua kumpulan subjek. Kawasan pengaktifan semasa tugasan WM adalah lebih luas berbanding SP. Akan tetapi, kumpulan subjek LHL memaparkan pengaktifan yang lebih simetri pada kawasan STG semasa tugasan SP dan WM. Ini menyokong penemuan terdahulu tentang kewujudan pengorganisasian semula korteks oleh subjek LHL. Untuk kesemua kumpulan subjek, ACG didapati mengalami pengaktifan yang lebih tinggi semasa WIN, menunjukkan kepentingan penglibatannya dalam pemprosesan SP dan WM dalam hingar yang dalam mana ACG memainkan peranan penting dalam fungsi eksekutif seperti tumpuan. Keputusan kehubungan efektif menunjukkan wujudnya interaksi di antara kawasan otak yang terlibat. Walau bagaimanapun, bagi tugasan SP, kehubungan ACGSTG untuk subjek RHL adalah tidak bererti (Kebarangkalian posterior, P < 0.9) berbanding subjek NH dan LHL yang mungkin menjadi penyebab kepada defisit dalam pemprosesan persepsi pertuturan. Ini kerana kedua-dua kawasan tersebut memainkan peranan penting dalam rangkaian frontal-temporal bagi persepsi pertuturan. Untuk WM, subjek NH menunjukkan kehubungan bererti (P > 0.9) yang sama antara kawasan terlibat di kedua - dua hemisfera. Untuk subjek LHL dan RHL, keserupaan dalam kehubungan bererti dengan subjek NH dapat diperhatikan pada satu hemisfera sahaja. Keputusan ini menunjukkan bahawa penglibatan kedua-dua hemisfera adalah amat penting dalam melaksanakan tugasan WM. Keputusan kajian mendapati hingar tidak mempengaruhi kehubungan efektif antara kawasan pengaktifan dalam semua kumpulan subjek untuk kedua-dua tugasan SP dan WM.,Verbal communication usually occurs in the presence of background noise causing difficulty for one to comprehend what is conveyed especially for those with unilateral hearing impairment. This is because the process may involve not only auditory areas but also several cognitive areas in the brain. Previous studies indicated evidence of cortical reorganisation to compensate the disability following unilateral hearing loss. However, little is known about the functional interactions in speech perception and working memory processing centers. Furthermore, the influences of the side of deafness and background noise on the cortical reorganisation are still unclear. This study was therefore carried out to determine the cortical reorganisation on the aspect of functional specialisation and effective connectivity of speech perception (SP) and working memory (WM) tasks performed in quiet and in noise. In this study, functional magnetic resonance imaging (fMRI) scans were performed on subjects with i) normal hearing in both ears (NH, n = 14), ii) right unilateral deafness (RHL, n = 6) and iii) left unilateral deafness (LHL, n = 6). Each subject performed SP and WM tasks in separate scans in which the subjects were binaurally presented with a series of five words alternately in silent (WIS) and in the presence of background noise (WIN). Statistical parametric mapping (SPM8) and dynamic causal modeling (DCM10) were used to determine brain functional specialisation and effective connectivity. For each subject, a number of 66 effective connectivity models for SP and 72 for WM were constructed for each hemisphere to test the existence of couplings between anterior cingulate cortex (ACG), primary auditory cortex (PAC), superior temporal gyrus (STG) and inferior frontal gyrus (IFG) with the addition of inferior parietal lobe (IPL) for WM. The results on functional specialisation showed bilateral activation for all groups in temporal, frontal and parietal lobes at uncorrected significant level (p<0.001). The activated areas during WM task are more extended than SP. However, LHL displayed more symmetrical activation in STG during SP and WM tasks. This support previous findings on the existence of cortical reorganisation for LHL subjects. For all subject groups, ACG was found to be activated higher during WIN indicating its important involvement in SP and WM processing in noise in which ACG plays an important role in executive function such as attention. The effective connectivity results show the existence of interactions between the regions of interest. However, for SP task, the ACGSTG connection for RHL subjects is not significant (Posterior probability, P < 0.90) as compared to NH and LHL subjects, which may likely be the cause of deficiency in processing speech perception. This is because both regions play important roles in the frontal-temporal network for speech perception. For WM, NH subjects showed the same significant (P > 0.90) connections between regions of interest in both hemispheres. For LHL and RHL subjects, similarity in significant connection with NH subjects is observed in only one hemisphere. These findings indicated that the co-involvement of the left and right hemispheres is vital in performing WM task. The results obtained from this study revealed that noise did not affect the effective connectivity between regions of interest in all subject groups for both SP and WM tasks.,Ph.D.
Pages:	232
Publisher:	UKM, Kuala Lumpur
Appears in Collections:	Faculty of Health Sciences / Fakulti Sains Kesihatan

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