Sains Malaysiana 44(9)(2015): 1339–1350

Kesan Penuaan ke atas Kehubungan Berkesan Otak semasa Pemprosesan Ingatan Bekerja daripada Perspektif Pemodelan Sebab dan Akibat Dinamik

(The Effect of Ageing on Brain Effective Connectivity during Working Memory Processing

from the Perspective of Dynamic Causal Modelling)

HANANI ABDUL MANAN^1,2, AHMAD NAZLIM YUSOFF^1* & SITI ZAMRATOL-MAI SARAH MUKARI³

¹Program Pengimejan Diagnostik & Radioterapi, Pusat Pengajian Sains Diagnostik dan Kesihatan Gunaan, Fakulti Sains Kesihatan, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz

50300 Kuala Lumpur, Wilayah Persekutuan, Malaysia

²Pusat Perkhidmatan dan Penyelidikan Neurosains (P3NEURO), Kampus Kesihatan, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan Darul Naim, Malaysia

³Program Audiologi, Pusat Pengajian Sains Rehabilitasi, Fakulti Sains Kesihatan, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Wilayah Persekutuan

Malaysia

Received: 8 January 2015/Accepted: 25 May 2015

ABSTRAK

Proses penuaan seringkali dikaitkan dengan kemerosotan sistem kognitif. Kemerosotan tersebut bermula seawal usia dua puluhan dan berterusan secara linear. Walau bagaimanapun, kesan penuaan ke atas ciri kehubungan antara kawasan otak masih belum difahami. Dalam kajian ini, pengimejan resonans magnet kefungsian (fMRI) digunakan untuk mengkaji kesan penuaan ke atas kehubungan otak yang terhasil daripada tugasan mengulang secara terbalik (BRT). Subjek normal dalam empat kumpulan umur iaitu 20-29 tahun (n=14), 30-39 tahun (n=14), 40-49 tahun (n=10) dan 50-65 tahun (n=14) mengambil bahagian dalam kajian ini. Stimulus BRT terdiri daripada satu siri lima perkataan yang diberi secara auditori. Pemetaan statistik berparameter (SPM) dan pemodelan sebab dan akibat dinamik (DCM) digunakan untuk menentukan pengaktifan dan kehubungan otak. Sebanyak 200 model kehubungan intrahemisfera dan 150 interhemisfera dibina bagi menguji kewujudan gandingan antara girus temporal superior (STG), girus Heschl (HG), talamus (TH) dan girus presentral (PCG) kesemua subjek. Keputusan DCM menunjukkan subjek keempat-empat kumpulan umur menggunakan kehubungan intrahemisfera yang sama semasa tugasan BRT. Kehubungan interhemisfera pula didapati berubah menjadi semakin kompleks apabila usia meningkat. Perubahan tersebut didapati bermula pada usia 40 tahun. Keputusan ini menyokong penemuan terdahulu bahawa penuaan menyebabkan perubahan pada sistem neuron otak seterusnya mempengaruhi pemprosesan kognitif.

Kata kunci: DCM; fungsi eksekutif pusat; fMRI; kehubungan efektif; pemprosesan auditori; penuaan

ABSTRACT

Ageing process is often associated with cognitive system declination. The decline begins as early as in the twenties and continues linearly. However, the effects of ageing on connectivity charactersistics between the brain areas have yet to be understood. In the present study, functional magnetic resonance imaging (fMRI) was used to investigate the effects of ageing on brain connectivity resulting from the backward repeat task (BRT). Normal participants with four age groups which were 20-29 years (n=14), 30-39 years (n=14), 40-49 years (n=10) and 50-65 years (n=14) participated in this study. The BRT stimulus consisted of a series of five words given auditorily. Statistical parametric mapping (SPM) and dynamic causal modeling (DCM) was used to determine brain activation and connectivity. Two-hundred intrahemispheric and 150 interhemispheric connectivity models were constructed to test the existence of coupling between superior temporal gyrus (STG), Heschl’s gyrus (HG), thalamus (TH) and precentral gyrus (PCG) on all subjects. DCM results showed that participants from the four age groups used the same intrahemispheric connectivity during BRT task. The interhemipheric connectivity changed and became more complex with ageing. The change was found to start at the age of 40. This result supports previous finding that ageing causes changes in the brain neuronal system and consequently affects cognitive processing.

Keywords: Ageing; auditory processing; central executive function; DCM; effective connectivity; fMRI

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  *Corresponding author; email: nazlimtrw@ukm.edu.my