Ahmad Nazlim Yusoff

• National University of Malaysia

Introduction There is increasing interest in the application of machine learning techniques to characterize structural brain anatomical magnetic resonance datasets. However, there are concerns regarding the selection of MR image feature types that can best characterize whole-brain anatomical differences. In this study, we compared the following ana...

INTRODUCTION: Different facets of divergent thinking (DT) are associated with connectivity between different cerebral areas. However, the causal interactions between the key DT nodes have yet to be explored. It is hypothesised that with creativity stimulation, changes in effective connectivity among regions will be observed. MATERIALS AND METHODS:...

Background: Resting-state functional magnetic resonance imaging (rs-fMRI) can evaluate brain functional connectivity without requiring subjects to perform a specific task. This rs-fMRI is very useful in patients with cognitive decline or unable to respond to tasks. However, long scan durations have been suggested to measure connectivity between br...

INTRODUCTION: Temporal lobe epilepsy (TLE) is a chronic disorder of the nervous system with focal seizures that may spread to other brain regions. Present knowledge regarding the spread of seizure is scarce. This study investigated activity in brain regions outside temporal lobe of TLE patient (TLEP) that may be affected by the spread. The findings...

Working memory (WM) capacity is the ability to maintain attention and store information briefly in the mind. However, each individual has a limited WM capacity that varies from one person to another. An individual can be categorized as having either normal or low WM capacity. This study aimed to evaluate and compare brain activations of healthy ind...

Background Alzheimer’s disease (AD) is a major neurocognitive disorder identified by memory loss and a significant cognitive decline based on previous level of performance in one or more cognitive domains that interferes in the independence of everyday activities. The accuracy of imaging helps to identify the neuropathological features that differe...

Background: Gaming can be very entertaining and through it, gamers are able to develop skills. However, it also may result in one’s getting too obsessed with video games regardless of any circumstances. Unnoticed, it may develop an Internet gaming disorder (IGD). This study aimed to investigate the neural activation involved in cognitive flexibilit...

Everyday spoken language processing does not occur in an ideal environment, but rather in the presence of interfering background noises such as from people talking, also known as babble noise. Babble noise as well as other types of noises have been found to be detrimental to speech perception processing and may lead to the degradation of the qualit...

The present study examined the impact of white noise on word recall performance and brain activity in 40 healthy adolescents, split in two groups (normal and low) depending on their auditory working memory capacity (AWMC). Using functional magnetic resonance imaging, participants performed a backward recall task under four different signal-to-noise...

Background: The auditory and prefrontal cortex supports auditory working memory processing. Many neuroimaging studies have shown hemispheric lateralization of auditory working memory brain regions in the presence of background noise, but few studies have focused on the lateralization of these regions during stochastic resonance. Purpose: To inve...

Research suggests that white noise may facilitate auditory working memory performance via stochastic resonance. Stochastic resonance is quantified by plotting cognitive performance as a function of noise intensity. The plot would appear as an inverted U-curve, that is, a moderate noise is beneficial for performance whereas too low and too much nois...

The relationship between resting effective connectivity (EC) among default mode network (DMN) regions and auditory working memory (AWM) performance is still poorly understood. In this work, resting-state functional magnetic resonance imaging (rsfMRI) was used to determine the optimum connectivity model between posterior cingulate cortex (PCC) and m...

Creativity is essential in daily decision making and problem solving. It is mainly indicated by divergent thinking tests. Previous studies have revealed the associated brain regions with divergent thinking tasks, but the segregation of functionally specialized cortices to different aspects of divergent thinking has not been explicitly addressed. Th...

Aging process is often associated with a deterioration in cognitive system. The decline begins as early as in the twenties and continues linearly. Other than that, the decline also becomes more pronounced in the presence of background noise. However, the effects of aging on the mechanisms of speech perception processing using forward repeat task (F...

High sensitivity signal detection for a sparse temporal sampling (STS) functional magnetic resonance imaging (fMRI) is compensated by the increase in the number of scans (N s) and consequently the scan time. A long scan time would result in fatigue and restlessness in participants, while a short scan time is undesirable for an STS-fMRI due to insuf...

This study aimed to model the psychophysiological interaction (PPI) between the bilateral STG and cerebellum (lobule VI and lobule VII) during an arithmetic addition task. Eighteen young adults participated in this study. They were instructed to solve single-digit addition tasks in quiet and noisy backgrounds during an fMRI scan. Results showed tha...

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, AHMAD NAZLIM YUSOFF* & SITI ZAMRATOL-MAI SARAH MUKARI AB...

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...

The present study used fMRI to investigate the neural basis of memory for verbal information using a forward repeat (FRT) and backward repeat task (BRT) administered in participants ranging between 20 and 65 years who were divided into four non-overlapping age groups. Results of behavioral performance on the FRT revealed no significant difference a...

Brain activation within, and psychophysiologic interaction between, significantly activated regions in the brain obtained from a phonological working memory experiment on a single participant were studied. Given that working memory and speech processing are key functions of human behaviour, this type of investigation is of fundamental importance to...

In the present study, brain activation associated with speech perception processing was examined across four groups of adult participants with age ranges between 20 and 65 years, using functional MRI (fMRI). Cognitive performance demonstrates that performance accuracy declines with age. fMRI results reveal that all four groups of participants activ...

This study was carried out to investigate the effects of noisy background on brain activation during a working memory task. Fourteen healthy male subjects underwent silent functional Magnetic Resonance Imaging (fMRI) scans while listening to words presented verbally against quiet (WIS) and noisy (WIN) backgrounds. The stimuli were binaurally presen...

Our brains respond to age-related anatomical and physiological changes by reorganizing functions through increases in activity or laterality shifts, among other possibilities. In suboptimal conditions such as in a noisy environment, the impact of ageing on brain functions is likely to be most apparent. The present study examined the effects of norm...

Everyday spoken language processing does not occur in a novel acoustic environment, but rather in the presence of the interfering background noise. In the present study, brain activation associated with speech perception (SP) processing in quiet (SPQ) and SP processing in 5-dB SNR noise (SPN) was examined in 15 healthy young adults using functional...

In spite of extensive research conducted in studying pitch memory processing, knowledge about the functional anatomy of the brain while performing pitch discrimination task is still lacking. The purpose of this study was to investigate the effects of background noise and tonal frequencies on brain activation during a pitch discrimination task. Thir...

Evidence suggests that cognitive performance deteriorates in noisy backgrounds and the problems are more pronounced in older people due to brain deficits and changes. The present study used functional MRI (fMRI) to investigate the neural correlates of this phenomenon during short-term memory using a forward repeat task performed in quiet (STMQ) and...

Background noise may impose deleterious effects on cognitive processing. However, noise below the threshold level may increase the ability to detect stimuli via stochastic resonance mechanisms (SR). The present study investigates whether task performance is deteriorated or enhanced by 5-dB SNR and, if the task performance is enhanced, whether this...

Brain activation within and effective connectivity between two significantly activated left and right primary motor regions (M1 left and M1 right) were modelled using functional magnetic resonance imaging datasets of seven subjects obtained from an externally triggered unilateral and bilateral finger tapping experiment. Unilateral tapping exhibited...

This fMRI study is about modelling the effective connectivity between Heschl's gyrus (HG) and the superior temporal gyrus (STG) in human primary auditory cortices. MATERIALS #ENTITYSTARTX00026; Ten healthy male participants were required to listen to white noise stimuli during functional magnetic resonance imaging (fMRI) scans. Statistical parametr...

Dynamic causal modeling (DCM) was implemented on datasets obtained from an externally-triggered finger tapping functional MRI experiment performed by 5 male and female subjects. The objective was to model the effective connectivity between two significantly activated primary motor regions (M1). The left and right hemisphere M1s are found to be effe...

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 a...

In spite of extensive research conducted to study how human brain works, little is known about a special function of the brain that stores and manipulates information-the working memory-and how noise influences this special ability. In this study, Functional magnetic resonance imaging (fMRI) was used to investigate brain responses to arithmetic pro...

Magnetic and microwave absorbing properties of thermoplastic natural rubber (TPNR) filled magnetite (Fe3O4) nanocomposites were investigated. The TPNR matrix was prepared from polypropylene (PP), natural rubber (NR) and liquid natural rubber (LNR) in the ratio of 70:20:10 with the LNR as the compatibilizer. TPNR-Fe3O4 nanocomposites with 4–12 wt% F...

Functional magnetic resonance imaging (fMRI) was used to investigate brain responses due to arithmetic working memory. Nine healthy young male subjects were given simple addition and subtraction instructions in noise and in quiet. The general linear model (GLM) and random field theory (RFT) were implemented in modelling the activation. The results...

This fMRI study is about modeling the intrinsic connectivity between Heschl' gyrus (HG) and superior temporal gyrus (STG) in human primary auditory cortices. Ten healthy male subjects participated and required to listen to white noise stimulus during the fMRI scans. Two intrinsic connectivity models comprising bilateral HG and STG were constructed...

Objective: This study investigates functional specialisation in, and effective connectivity between the precentral gyrus (PCG) and supplementary motor area (SMA) in seven right handed female subjects. Methods: Unimanual (UNIright and UNIleft) and bimanual (BIM) self-paced tapping of hand fingers were performed by the subjects to activate PCG and SM...

The magnetic properties of magnetite nanoparticles and magnetite‐thermoplastic natural rubber (TPNR) nanocomposites was prepared by melt‐blending method has been studied using vibrating sample magnetometer (VSM). The saturation magnetization (MS), remanence (MR), squareness (MR/MS), coercivity (HC) and exchange‐bias field (Heb) for magnetite nanopa...

A sample of Ni0.25Co0.25Zn0.5Fe2O4 ferrite was prepared by a double-staged sintering method in air. Thermoplastic natural rubber (TPNR) was prepared by melt blending of natural rubber (NR), liquid natural rubber (LNR), and high density polyethylene (HDPE) in an internal mixer Brabender Plasticorder PL 2000. Magnetic polymer composites were prepared...

A functional magnetic resonance imaging (fMRI) examination was carried out on a healthy male and female subject to study brain activation during overt and covert readings. The study was conducted on a 1.5 T magnetic resonance imaging (MRI) system (Siemens VB33G) in the Department of Radiology, Universiti Kebangsaan Malaysia Hospital. The task, in a...

ABSTRAK Kajian garis pangkal pengimejan resonans magnet kefungsian (fMRI) telah dijalankan ke atas 2 orang subjek lelaki sihat dominan tangan kanan dan kiri. Kajian ini menggunakan gerakan jari tangan kanan dan kiri untuk merangsang aktiviti neuron di dalam korteks serebrum. Subjek diarahkan supaya menekan jari-jari pada ibu jari secara bergilir-gi...

The complex scattering parameters (S-11* and S-21*), relative dielectric permittivity (epsilon(r)* = epsilon(r)* - and j epsilon(r)*), relative magnetic permeability (mu(r)* = mu(r)' - j mu(r)") and absorption characteristics of some thermoplastic natural rubber (TPNR) - Fe3O4/YIG composites were investigated using a microwave vector network analys...

The complex scattering parameters (S11*, S21*, S12* and S22*), microwave dielectric permittivity (εr*=εr′−jεr″), magnetic permeability (μr*=μr′−jμr″) and absorption characteristics of an undoped and doped samples (1 wt% CuO and MgO) of (Li0.5Fe0.5)0.7Zn0.3Fe2O4 (LiZn ferrite) were measured using a microwave vector network analyzer by means of coaxi...

A microwave (Li0.5Fe0.5)0.4Ni0.3Zn0.3Fe2O4 (LNZ) ferrite was prepared by a conventional sintering method in air. Thermoplastic natural rubber (TPNR) was prepared from polypropylene (PP) and natural rubber (NR) in the ratios of 80:20, 70:30, 60:40, 50:50 and 40:60 with liquid natural rubber as a compatibilizer by a melt blending technique. LNZ ferri...

Electromagnetic properties of a thermoplastic natural rubber (TPNR), a lithium–nickel–zinc (Li–Ni–Zn) ferrite and a TPNR–ferrite composite subjected to transverse electromagnetic (TEM) wave propagation were investigated. The incorporation of the ferrite into the matrix of the TPNR was found to reduce the dielectric loss but the magnetic loss increa...

Complex impedances of some magnesium-zinc ferrites, MgxZn1-xFe2O4 (x=0.4, 0.5, 0.6 and 0.7), in the frequency range of 1 mHz-10 MHz were measured at 300 K. The complex-plane impedance spectrum from each sample indicates that the capacitive and the resistive properties of the materials are mainly attributed to the processes that associated with the...

Complex impedances of a sintered polycrystalline Mg0.5Zn0.5Fe2O4 ferrite in the frequency range of 15 mHz to 13 MHz were measured at several temperatures in the range of 273–373 K. The complex-plane impedance spectra indicate that the material can be represented by a two-layer leaky capacitor which corresponds to the bulk and the grain boundary phe...

A functional magnetic resonance imaging (fMRI) study was conducted on 4 healthy male and female subjects to investigate brain activation during passive and active listening. Two different experimental conditions were separately used in this study. The first condition requires the subjects to listen to a simple arithmetic instruction (e.g. one-plus-...