Resting State Effective Connectivity between Inferior Parietal Lobe (IPL) and Inferior Temporal Gyrus (ITG) in the Left and Right Hemispheres / Jurnal Sains Kesihatan Malaysia

Inferior parietal lobule (IPL) and inferior temporal gyrus (ITG) are two important brain regions for the default modenetwork (DMN). IPL has been known to be involved in the control of attention and responding to given information whileITG is involved in the processing and perception awakened by visual stimuli. These two key DMN regions are highlyinterconnected as determined from white matter and fiber tracking studies. However, little is known about their natureof connectivity while the brain is at rest, whether it is linear, bilinear or nonlinear and whether it is of mono- or bidirection.Resting state functional magnetic resonance imaging (rsfMRI) data were obtained from 7 healthy male andfemale participants (average age = 20.7 ± 4.5 years) and were concatenated. Data were analyzed using statisticalparametric mapping (SPM12). Endogenous brain signals were modelled by Fourier series at 0.01 – 0.08 Hz. IPL-ITGconnected linear, bilinear and non-linear causal models in both hemispheres were constructed and estimated by means ofstochastic dynamic causal modelling (sDCM) and were compared using Bayesian Model Selection (BMS) for group studies.Group fixed-effects results indicated that bilateral IPL and ITG exhibited high neural activity at a corrected significantlevel (pFWE 1000) which has the best balance betweenmodel accuracy and difficulty. The minimum free energy (F) = -4.41 × 104 and -4.09 × 104 for left and right hemispherebilinear models respectively. From BMS and DCM results, it was found that IPL and ITG do have a dynamic collaborationbetween each other, a connectivity that belongs to a greater network when the brain is at rest. The intrinsic connectionsbetween them are negative in both directions i.e. IPL and ITG mutually inhibited each other. The effective connectivitywas modulated by the endogenous fluctuation of the brain signal.

Brain Activation Display Functional Asymmetry in Response to Action, Background and Tonal Frequency During a Pitch Memory Processing: An fMRI Study / Jurnal Sains Kesihatan Malaysia

@#In this study, the asymmetry of the main effects of action, background and tonal frequency during a pitch memory processingwere investigated by means of brain activation. Eighteen participants (mean age 27.6 years) were presented with low andhigh frequency tones in quiet and in noise. They listen, discriminate and recognize the target tone against the final tonein a series of four distracting tones. The main effects were studied using the analysis of variance (ANOVA) with action (towring (rubber bulb) vs. not to wring), background (in quiet vs. in noise) and frequency (low vs. high) as the factors (andlevels respectively). The main effect of action is in the right pre-central gyrus (PCG), in conformation with its contralateralbehavior. The main effect of background indicated the bilateral primary auditory cortices (PAC) and is right lateralized,attributable to white noise. The main effect of frequency is also observed in PAC but bilaterally equal and attributable tolow frequency tones. Despite the argument that the temporo-spectral lateralization dichotomy is not especially rigid asrevealed by the main effect of frequency, right lateralization of PAC for the respective main effect of background clearlydemonstrates its functional asymmetry suggesting different perceptual functionality of the right and left PAC.

Functional MRI Characteristics in Visual Cortex (BA 17, 18 and 19) Corresponding to the Visual Field of Normal, Glaucoma Suspect (GS) and Primary Open Angle Glaucoma (POAG) Patients / Jurnal Sains Kesihatan Malaysia

The purpose of this study was to characterize, differentiate and correlate visual field and brain activation in visual cortex for normal, glaucoma suspect (GS) and primary open angle glaucoma (POAG) participants using Standard Automated Perimetry (SAP) and functional Magnetic Resonance Imaging (fMRI) respectively. The fMRI scans and SAP test were both carried out in Pusat Perubatan Universiti Kebangsaan Malaysia (PPUKM). Two types of black-and-white checkerboard pattern were displayed to the participants during the fMRI scans. The fMRI data were analyzed using WFU pickatlas toolbox targeting visual cortex area. The results showed that there was no significant difference in number of activated voxel between the three groups in visual cortex (BA 17, 18 and 19) while viewing all the given stimuli (p > 0.05). The pattern standard deviation (PSD) of SAP for visual field also revealed no significant differences (p > 0.05) in all groups of participants. However, negative correlation between PSD and fMRI activation was observed. The PSD values increased with a decrease in fMRI activation. With reference to visual field analysis, the results suggest that glaucomatous neuropathy of POAG patients has led to a gradual decrease in visual cortex activation and a gradual increase in PSD.

Superior Temporal Gyrus (STG) and Cerebellum Show Different Activation Profile during Simple Arithmetic Addition Task in Quiet and in Noisy Environment: An fMRI Study / Jurnal Sains Kesihatan Malaysia

Despite a vast number of studies that were focused on the roles of superior temporal gyrus (STG) and cerebellum as sensory area, little is known about their involvement in cognitive function such as attention and perception. The present fMRI study aimed to identify this cognitive role from brain activation profile of STG and cerebellum obtained from an arithmetic addition task. Eighteen healthy right hand dominance male adults participated in this study. They were instructed to solve single-digit addition tasks in quiet and noisy background during the fMRI scan. Both the in-quiet and in-noise addition tasks activated the bilateral STG and cerebellum (lobule VI and lobule VII) significantly but differentially. In both quiet and noisy conditions, STG activation is dominant in the left hemisphere while cerebellum showed a right hemisphere dominance. Bilateral STG and cerebellum (lobule VI) activation decreasedin noise, conversely cerebellum (lobule VII) activation increased in noise. These asymmetrical activation indicated hemispheric lateralization and differential behaviors of both brain areas in different environment while performing simple arithmetic addition task.

Investigating Brain Activation and Neural Effi cacy During Simple Arithmetic Addition Task in Quiet and in Noise: An fMRI Study / Jurnal Sains Kesihatan Malaysia

Knowledge about the hemodynamic model that mediates synaptic activity and measured magnetic resonance signal is essential in understanding brain activation. Neural effi cacy is a hemodynamic parameter that would change the evoked hemodynamic responses. In this work, brain activation and neural effi cacy of the activated brain areas during simple addition task in two different backgrounds were studied using fMRI. The objectives were to determine the activated areas during the performance of arithmetic addition in quiet (AIQ) and noisy (AIN) background and to investigate the relationship between neural effi cacy and height extent of activation for the respective areas. Eighteen healthy male participants performed simple arithmetic addition in quiet and in noise. Bilateral cerebellum, superior temporal gyrus (STG), temporal pole (TP) and supplementary motor area (SMA) were signifi cantly (p < 0.05) activated during AIQ and AIN. Left middle frontal gyrus (L-MFG), right superior frontal gyrus (R-SFG), right superior orbital gyrus (R-SOG) and bilateral insula were more active in quiet as compared to in noise while the left middle cingulate cortex (L-MCC), left amygdala (L-AMG), right temporal pole (R-TP) and left cerebellum (L-CER) were more active in noise as compared to in quiet. The t value for most of the activated regions was found to be inversely proportional to the neural effi cacy. Signifi cant (p < 0.05) negative relationship between t value and neural effi cacy were found for R-STG and bilateral cerebellum during AIQ, while for AIN, similar relationships were found in R-CER, R-STG and R-TP. This study suggests that while being signifi cantly activated, the hemodynamic responses of these brain regions could have been suppressed by the stimulus resulting in an intensity decrease with increasing neural efficacy

The Effects of Tapping Force and Speed on the Activation of Motor-related Cortices / Jurnal Sains Kesihatan Malaysia

This single participant functional magnetic resonance imaging (fMRI) study investigates the effects of tapping force and speed on the activation characteristics in motor-related cortices during bilateral self-paced tapping of hand fi ngers. The participant performed four types of self-paced hand fi nger tapping which are soft-slow (SS), soft-fast (SF), hard-slow (HS) and hard-fast (HF) in an fMRI scan. A general linear model (GLM) was implemented in generating brain activation. Statistical inferences were then made about the brain activations using Gaussian random fi eld theory (RFT) at corrected signifi cant level (α = 0.05), given that there is no activation. The results indicate that the brain coordinates bilateral selfpaced tapping of hand fi ngers with the involvement of motor-related cortices which are bilateral precentral gyrus (PCG), bilateral cerebellum and supplementary motor area (SMA). The increase in tapping force accentuate signifi cant activation (p < 0.05 corrected) in bilateral PCG (Brodmann Area (BA) 6) in accordance with its function in triggering motor action such as controlling the tapping force. The increase in tapping speed causes a signifi cant (p < 0.05 corrected) increase in brain activation only in somatosensory associated region in the right superior parietal lobule (SPL) or right BA7. This suggests that SPL plays important roles in coordinating purposeful, skilled movements

Brain Activation during Addition and Subtraction Tasks In-Noise and In-Quiet

Background: 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 problems solved in noisy and quiet backgrounds. Methods: Eighteen healthy young males performed simple arithmetic operations of addition and subtraction with in-quiet and in-noise backgrounds. The MATLAB-based Statistical Parametric Mapping (SPM8) was implemented on the fMRI datasets to generate and analyse the activated brain regions. Results: Group results showed that addition and subtraction operations evoked extended activation in the left inferior parietal lobe, left precentral gyrus, left superior parietal lobe, left supramarginal gyrus, and left middle temporal gyrus. This supported the hypothesis that the human brain relatively activates its left hemisphere more compared with the right hemisphere when solving arithmetic problems. The insula, middle cingulate cortex, and middle frontal gyrus, however, showed more extended right hemispheric activation, potentially due to the involvement of attention, executive processes, and working memory. For addition operations, there was extensive left hemispheric activation in the superior temporal gyrus, inferior frontal gyrus, and thalamus. In contrast, subtraction tasks evoked a greater activation of similar brain structures in the right hemisphere. For both addition and subtraction operations, the total number of activated voxels was higher for in-noise than in-quiet conditions. Conclusion: These findings suggest that when arithmetic operations were delivered auditorily, the auditory, attention, and working memory functions were required to accomplish the executive processing of the mathematical calculation. The respective brain activation patterns appear to be modulated by the noisy background condition.

Functional Specialisation and Effective Connectivity During Self-paced Unimanual and Bimanual Tapping of Hand Fingers: An Extended Analysis Using Dynamic Causal Modeling and Bayesian Model Selection for Group Studies

Introduction: This multiple-subject fMRI study continue to further investigate brain activation within and effective connectivity between the significantly (p<0.001) activated primary motor area (M1), supplementary motor area (SMA) with the inclusion of BA44 during unimanual (UNIright and UNIleft) and bimanual (BIM) self-paced tapping of hand fingers. Methods: The activation extent (spatial and height) and effective connectivity were analysed using statistical parametric mapping (SPM), dynamic causal modeling (DCM) and the novel method of Bayesian model selection (BMS) for group studies. Results: Group results for UNIright and UNIleft showed contra-lateral and ipsi-lateral involvement of M1 and SMA. The results for BIM showed bilateral activation in M1, SMA and BA44. A larger activation area but with lower percentage of signal change (PSC) are observed in the left M1 due to the control on UNIright as compared to the right M1 due to the control on UNIleft. This is discussed as due to the influence of the tapping rate effects that is greater than what would be produced by the average effects of the dominant and sub-dominant hand. However, the higher PSC observed in the right M1 is due to a higher control demand used by the brain in coordinating the tapping of the sub-dominant hand fingers. Connectivity analysis indicated M1 as the intrinsic input for UNIright and UNIleft while for BIM, the inputs were both M1s. During unilateral finger tapping, the contra-lateral M1 acts as the input center which in turn triggers the propagation of signal unidirectionally to other regions of interest. The results obtained for BIM (BIMleft and BIMright) however yield a model with less number of significant connection. M1-M1 connection is unidirectional for UNIleft and UNIright originating from contra-lateral M1, and is inhibited during BIM. Conclusion: By taking into consideration the presence of outliers that could have arisen in any subject under study, BMS for group study has successfully chosen a model that has the best balance between accuracy (fit) and complexity.

Functional Specialisation and Effective Connectivity in Cerebral Motor Cortices: An fMRI Study on Seven Right Handed Female Subjects

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 SMA. Brain activations and effective connectivity were analysed using statistical parametric mapping (SPM), dynamic causal modeling (DCM) and Bayesian model selection (BMS) and were reported based on group fixed (FFX) and random (RFX) effects analyses. Results: Group results showed that the observed brain activation for UNIright and UNIleft fulfill contralateral behavior of motor coordination with a larger activation area for UNIright. The activation for BIM occurs in both hemispheres with BIMright showing higher extent of activation as compared to BIMleft. Region of interest (ROI) analyses reveal that the number of activated voxel (NOV) and percentage of signal change (PSC) on average is higher in PCG than SMA for all tapping conditions. However, comparing between hemispheres for both UNI and BIM, higher PSC is observed in the right PCG and the left SMA. DCM and BMS results indicate that most subjects prefer PCG as the intrinsic input for UNIright and UNIleft. The input was later found to be bi-directionally connected to SMA for UNIright.The bi-directional model was then used for BIM in the left and right hemispheres. The model was in favour of six out of seven subjects. DCM results for BIM indicate the existance of interhemispheric connectivity between the right and left hemisphere PCG. Conclusion: The findings strongly support the existence of functional specialisation and integration i.e. effective connectivity in human brain during finger tapping and can be used as baselines in determining the probable motor coordination pathways and their connection strength in a population of subjects

Activation Characteristics of the Primary Motor (M1) and Supplementary Motor (SMA) Areas during Robust Unilateral Finger Tapping Task / Jurnal Sains Kesihatan Malaysia

This study investigated the functional specialisation characteristics of brain in multiple right-hand dominant subjects pertaining to the activation of the cerebral motor cortices evoked by unilateral finger tapping, especially in primary motor (M1) and supplementary motor (SMA) areas. This multiple-subject study used unilateral (UNIright and UNIleft) selfpaced tapping of hand fingers to activate the M1 and SMA. Brain activation characteristics were analysed using statistical parametric mapping (SPM). Activation for UNIright and UNIleft showed the involvement of contralateral and ipsilateral M1 and SMA. A larger activation area but with a lower percentage of signal change (PSC) were observed in the left M1 due to the control on UNIright (4164 voxels at α = 0.001, PSC = 1.650) as compared to the right M1 due to the control on UNIleft (2012 voxels at α = 0.001, PSC = 2.377). This is due to the influence of the tapping rate effects which is greater than what could be produced by the average effects of the dominant and sub-dominant hands. The significantly higher PSC value observed in the right M1 (p < 0.05) is due to a higher control demand used by the brain in coordinating the tapping of the sub-dominant fingers. The findings obtained from this study showed strong evidence of the existence of brain functional specialisation and could be used as baseline references in determining the most probable motor pathways in a sample of subjects.

Brain Activations Evoked by Passive and Active Listening: A Preliminary Study on Multiple Subjects / Jurnal Sains Kesihatan Malaysia

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-two-plus-three-plus-four) – passive listening. In the second condition, the subjects were given the same series of arithmetic instruction and were required to listen and perform the calculation – active listening. The data were then analysed using the Statistical Parametric Mapping (SPM5) and the MATLAB 7.4 (R2007a) programming softwares. The results obtained from the fixed (FFX) and random effects analyses (RFX) show that the active-state signal intensity was significantly higher (p < 0.05) than the resting-state signal intensity for both conditions. The results also indicate significant differences (p < 0.001) in brain activation between passive and active listening. The activated cortical regions during passive listening, as obtained from the FFX of the first condition is symmetrical in the left and right temporal and frontal lobes covering the cortical auditory areas. However, for the second condition, which was active listening, more activation occurs in the left hemisphere with a reduction in the number of activated voxels and their signal intensity in the right hemisphere. Activation mainly occurs in the middle temporal gyrus, precentral gyrus, middle frontal gyrus, superior temporal gyrus and several other areas in the frontal lobes. The point of maximum signal intensity has been shifted to a new coordinates during active listening. It is also observed that the magnetic resonance signal intensity and the number of activated voxel in the right and left superior temporal lobes for the second condition have been reduced as compared to that of the first condition. The results obtained strongly suggest the existence of functional specialisation. The results also indicate different networks for the two conditions. These networks clearly pertain to the existence of functional connectivity between activation areas during listening and listening while performing a simple arithmetic task.