Original Article Published on 02 Oct, 2012

The Acquisition, Analyses and Interpretation of fMRI Data: A Study on Functional Specialisation in Primary Auditory Cortices

Vol. 3 No. 2 : 2008 (300-317)

Yusoff AN Yusoff AN
Abdul Hamid K Abdul Hamid K
Mohamad M Mohamad M
Abd Hamid AI Abd Hamid AI

Abstract
In this study, functional magnetic resonance imaging (fMRI) is used to investigate func­tional specialisation in human auditory cortices during listening. A silent fMRI paradigm was used to reduce the scanner sound artefacts on functional images. The subject was instructed to pay attention to the white noise stimulus binaurally given at an inten­sity level of 70 dB higher than the hearing level for normal people. Functional speciali­sation was studied using the Matlab-based Statistical Parametric Mapping (SPM5) software by means of fixed effects (FFX), random effects (RFX) and conjunction analyses. Individual analyses on all subjects indicated asymmetrical bilateral activation of the left and right hemispheres in Brodmann areas (BA) 22, 41 and 42, involving the primary and secondary auditory corti­ces. The percentage of signal change is larger in the BA22, 41 and 42 on the right as compared to the ones on the left (p>0.05). The average number of activated voxels in all the respective Brodmann areas are higher in the right hemisphere than in the left (p>0.05). FFX results showed that the point of maximum intensity was in the right BA41 whereby 599±1 activated voxels were ob­served in the right temporal lobe as compared to 485±1 in the left temporal lobe. The RFX results were consistent with that of FFX. The analysis of conjunction which fol­lowed, showed that the right BA41 and left BA22 as the common acti­vated areas in all subjects. The results confirmed the specialisation of the right auditory cortices in pro­cessing non verbal stimuli.
Keywords : Brodmann Area (BA), Conjunc-tion analysis, Fixed-effects analysis (FFX), Functional Magnetic Reso¬nance Imaging (fMRI), Random-effects analysis (RFX), Statistical Parametric Mapping (SPM),
Abstrak
Dalam kajian ini, pengimejan resonans magnet kefungsian (fMRI) digunakan untuk meng­kaji pengkhususan kefungsian dalam korteks auditori manusia semasa mende­ngar. Para­digma fMRI senyap digunakan untuk mengurangkan artifak bunyi pengim­bas di atas imej kefungsian. Subjek dikehendaki menumpukan perhatian kepada stimulus hingar putih yang diperdengarkan secara binaural pada keamatan 70 dB lebih tinggi daripada aras pendengaran manusia normal. Pengkhususan kefungsian dikaji menggunakan perisian Pemetaan Statistik Berparameter (SPM5) yang berasaskan Matlab melalui analisis kesan malar (FFX), kesan rawak (RFX) dan konjunksi. Analisis individu ke atas semua subjek menunjukkan pengaktifan bilateral yang tidak simetri di antara hemisfera kanan dan kiri pada kawasan Brodmann (BA) 22, 41 dan 42, meli­batkan korteks auditori primer dan se­kunder. Peratus perubahan isyarat didapati lebih besar di ketiga-tiga BA22, 41 dan 42 ka­nan berbanding dengan yang di sebelah kiri (p>0.05). Purata bilangan voksel aktif bagi kesemua kawasan Brodmann tersebut  juga didapati lebih tinggi di hemisfera kanan ber­banding dengan kiri (p>0.05). Keputusan FFX menunjukkan titik pengaktifan maksimum berlaku pada BA41 kanan dengan se­banyak 599±1 voksel aktif dicerap di lobus temporal kanan berbanding 485±1 di lobus temporal kiri. Keputusan FFX didapati tekal dengan keputusan purata bagi kesemua subjek. Analisis konjunksi kemudiannya menunjukkan BA41 kanan dan BA22 kiri se­bagai kawasan pengaktifan sepunya dalam kesemua subjek.  Keputusan yang diperolehi mengesahkan pengkhususan korteks auditori kanan dalam pemprosesan stimulus bukan pertuturan.
Kata Kunci : Analisis kesan malar (FFX), Analisis kesan rawak (RFX), Analisis kon-junksi, Kawasan Brodmann (BA), Pemetaan Statistik Berparameter (SPM), Pengimejan Resonans Magnet Kefungsian (fMRI),

Correspondance Address
Associate Professor Dr. Ahmad Nazlim Yusoff, Program Pengimejan Diagnostik & Radioterapi, Fakulti Sains Kesihatan Bersekutu Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz 50300 Kuala Lumpur. Email: nazlim@medic.ukm.my


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