Sains Malaysiana 40(6)(2011): 665–678
Pemerolehan, Analisis dan Interpretasi Data fMRI:
Kehubungan Efektif dalam Korteks Auditori Primer Manusia
(Acquisition, Analyses and Interpretation of fMRI Data: A
Study on the Effective Connectivity in Human Primary Auditory Cortices)
Ahmad
Nazlim Yusoff*, Mazlyfarina Mohamad, Khairiah Abdul Hamid & Aini Ismafairus
Abd Hamid
Makmal
Pemprosesan Imej Kefungsian (FIPL), Program Pengimejan Diagnostik & Radioterapi
Fakulti
Sains Kesihatan Bersekutu, Universiti Kebangsaan Malaysia, 50300 Jalan Raja
Muda Abdul Aziz, Kuala Lumpur, Malaysia
Siti
Zamratol-Mai Sarah Mukari
Jabatan
Audiologi & Sains Pertuturan, Fakulti Sains Kesihatan Bersekutu, Universiti
Kebangsaan Malaysia, 53200 Jalan Temerloh, Kuala Lumpur, Malaysia
Diserahkan:
27 November 2008 / Diterima: 29 November 2010
ABSTRAK
Kajian ke atas sifat kehubungan efektif dalam korteks auditori
dilakukan ke atas lima orang subjek Melayu lelaki sihat berumur antara 20
hingga 40 tahun menggunakan pengimejan resonans magnet kefungsian (fMRI),
pemetaan statistik berparameter (SPM5) dan pemodelan dinamik penyebab (DCM).
Paradigma pengimejan 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 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 korteks auditori kanan dan kiri pada
kawasan Brodmann (BA)22, 41 dan 42 melibatkan korteks
auditori primer dan sekunder. Tiga kawasan auditori di korteks auditori kanan
dan kiri tersebut dipilih untuk penentuan kehubungan efektif melalui
pembentukan sembilan model rangkaian. Kehubungan efektif ditentukan ke atas
empat daripada lima subjek dengan mengecualikan seorang subjek yang mempunyai
koordinat BA22 yang terletak terlalu jauh daripada koordinat BA22 yang
diperoleh daripada analisis kumpulan. Keputusan DCM menunjukkan
kewujudan kehubungan efektif di antara ketiga-tiga kawasan auditori yang
dipilih di kedua-dua korteks auditori. Pada korteks auditori kanan, BA42
dikenalpasti sebagai pusat masukan dengan kehubungan efektif satu arah selari
BA42 → BA41
dan BA42 → BA22. Walau bagaimanapun, untuk korteks auditori kiri,
pusat masukan adalah BA41 dengan kehubungan efektif satu arah selari BA41→BA42
dan BA41→BA22. Kehubungan di antara kawasan auditori yang
mengalami pengaktifan mencadangkan kewujudan lintasan isyarat dalam korteks
auditori walaupun semasa subjek mendengar bunyi hingar.
Kata kunci: Kawasan Brodmann; Pemetaan Statistik Berparameter;
Pemodelan dinamik penyebab, Pengimejan Resonans Magnet Kefungsian
ABSTRACT
A study on the effective connectivity characteristics in
auditory cortices was conducted on five healthy Malay male subjects with the
age of 20 to 40 years old using functional magnetic resonance imaging (fMRI),
statistical parametric mapping (SPM5) and dynamic causal modelling (DCM).
A silent imaging paradigm was used to reduce the scanner sound artefacts on
functional images. The subjects were instructed to pay attention to the white
noise stimulus binaurally given at intensity level of 70 dB higher than the
hearing level for normal people. Functional specialisation was studied using
Matlab-based SPM5 software by means of fixed effects (FFX),
random effects (RFX) and conjunction analyses.
Individual analyses on all subjects indicate asymmetrical bilateral activation
between the left and right auditory cortices in Brodmann areas (BA)22, 41 and
42 involving the primary and secondary auditory cortices. The three auditory
areas in the right and left auditory cortices are selected for the
determination of the effective connectivity by constructing 9 network models.
The effective connectivity is determined on four out of five subjects with the
exception of one subject who has the BA22 coordinates located too far from BA22
coordinates obtained from group analysis. DCM results
showed the existence of effective connectivity between the three selected
auditory areas in both auditory cortices. In the right auditory cortex, BA42 is
identified as input centre with unidirectional parallel effective
connectivities of BA42 → BA41 and BA42 → BA22. However, for the left auditory cortex,
the input is BA41 with unidirectional parallel effective connectivities of BA41→BA42
and BA41→BA22. The connectivity between the activated auditory
areas suggests the existence of signal pathway in the auditory cortices even
when the subject is listening to noise.
Keywords: Brodmann
Area; Dynamic causal modeling; Functional Magnetic Resonance Imaging;
Statistical Parametric Mapping
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*Pengarang untuk
surat-menyurat; email: nazlim@medic.ukm.my
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