MyMedR

Displaying all 12 publications

Abstract:

Sort:

Early visual analysis tool using magnetoencephalography for treatment and recovery of neuronal dysfunction

Rasheed W, Neoh YY, Bin Hamid NH, Reza F, Idris Z, Tang TB

Comput Biol Med, 2017 10 01;89:573-583.
PMID: 28551109 DOI: 10.1016/j.compbiomed.2017.05.005

Functional neuroimaging modalities play an important role in deciding the diagnosis and course of treatment of neuronal dysfunction and degeneration. This article presents an analytical tool with visualization by exploiting the strengths of the MEG (magnetoencephalographic) neuroimaging technique. The tool automates MEG data import (in tSSS format), channel information extraction, time/frequency decomposition, and circular graph visualization (connectogram) for simple result inspection. For advanced users, the tool also provides magnitude squared coherence (MSC) values allowing personalized threshold levels, and the computation of default model from MEG data of control population. Default model obtained from healthy population data serves as a useful benchmark to diagnose and monitor neuronal recovery during treatment. The proposed tool further provides optional labels with international 10-10 system nomenclature in order to facilitate comparison studies with EEG (electroencephalography) sensor space. Potential applications in epilepsy and traumatic brain injury studies are also discussed.

Matched MeSH terms: Magnetoencephalography*
Localized N20 Component of Somatosensory Evoked Magnetic Fields in Frontoparietal Brain Tumor Patients Using Noise-Normalized Approaches

Elaina NS, Malik AS, Shams WK, Badruddin N, Abdullah JM, Reza MF

Clin Neuroradiol, 2018 Jun;28(2):267-281.
PMID: 28116447 DOI: 10.1007/s00062-017-0557-0

PURPOSE: To localize sensorimotor cortical activation in 10 patients with frontoparietal tumors using quantitative magnetoencephalography (MEG) with noise-normalized approaches.
MATERIAL AND METHODS: Somatosensory evoked magnetic fields (SEFs) were elicited in 10 patients with somatosensory tumors and in 10 control participants using electrical stimulation of the median nerve via the right and left wrists. We localized the N20m component of the SEFs using dynamic statistical parametric mapping (dSPM) and standardized low-resolution brain electromagnetic tomography (sLORETA) combined with 3D magnetic resonance imaging (MRI). The obtained coordinates were compared between groups. Finally, we statistically evaluated the N20m parameters across hemispheres using non-parametric statistical tests.
RESULTS: The N20m sources were accurately localized to Brodmann area 3b in all members of the control group and in seven of the patients; however, the sources were shifted in three patients relative to locations outside the primary somatosensory cortex (SI). Compared with the affected (tumor) hemispheres in the patient group, N20m amplitudes and the strengths of the current sources were significantly lower in the unaffected hemispheres and in both hemispheres of the control group. These results were consistent for both dSPM and sLORETA approaches.
CONCLUSION: Tumors in the sensorimotor cortex lead to cortical functional reorganization and an increase in N20m amplitude and current-source strengths. Noise-normalized approaches for MEG analysis that are integrated with MRI show accurate and reliable localization of sensorimotor function.

Matched MeSH terms: Magnetoencephalography*
Fulltext Robust EEG/MEG Based Functional Connectivity with the Envelope of the Imaginary Coherence: Sensor Space Analysis

Sanchez Bornot JM, Wong-Lin K, Ahmad AL, Prasad G

Brain Topogr, 2018 11;31(6):895-916.
PMID: 29546509 DOI: 10.1007/s10548-018-0640-0

The brain's functional connectivity (FC) estimated at sensor level from electromagnetic (EEG/MEG) signals can provide quick and useful information towards understanding cognition and brain disorders. Volume conduction (VC) is a fundamental issue in FC analysis due to the effects of instantaneous correlations. FC methods based on the imaginary part of the coherence (iCOH) of any two signals are readily robust to VC effects, but neglecting the real part of the coherence leads to negligible FC when the processes are truly connected but with zero or π-phase (modulus 2π) interaction. We ameliorate this issue by proposing a novel method that implements an envelope of the imaginary coherence (EIC) to approximate the coherence estimate of supposedly active underlying sources. We compare EIC with state-of-the-art FC measures that included lagged coherence, iCOH, phase lag index (PLI) and weighted PLI (wPLI), using bivariate autoregressive and stochastic neural mass models. Additionally, we create realistic simulations where three and five regions were mapped on a template cortical surface and synthetic MEG signals were obtained after computing the electromagnetic leadfield. With this simulation and comparison study, we also demonstrate the feasibility of sensor FC analysis using receiver operating curve analysis whilst varying the signal's noise level. However, these results should be interpreted with caution given the known limitations of the sensor-based FC approach. Overall, we found that EIC and iCOH demonstrate superior results with most accurate FC maps. As they complement each other in different scenarios, that will be important to study normal and diseased brain activity.

Matched MeSH terms: Magnetoencephalography/methods*
Fulltext Assessing neuroplasticity using magnetoencephalography (MEG) in patient with left-Temporo-Parietal Pilocytic Astrocytomas treated with endoscopic surgery

Hanani Abdul Manan, Zamzuri Idris, Jafri Malin Abdullah, Mohammed Faruque Reza, Hazim Omar

Jurnal Sains Kesihatan Malaysia, 2018;16(1):63-69.
MyJurnal

Neuroplasticity has been subjected to a great deal of research in the last century. Recently, significant emphasis has been
placed on the global effect of localized plastic changes throughout the central nervous system, and on how these changes
integrate in a pathological context. The present study aimed to demonstrate the functional cortical reorganization before
and after surgery using magnetoencephalography (MEG) in a participant with brain tumor. Results of Visual Evoked
Magnetic Field (VEF) based on functional MEG study revealed significantly different of MEG N100 waveforms before and
after surgery. Larger and additional new locations for visual activation areas after the surgery were found suggesting
neuroplasticity. The present study highlight a physiological plasticity in a teenage brain and the alterations regarding
neural plasticity and network remodeling described in pathological contexts in higher-order visual association areas.

Matched MeSH terms: Magnetoencephalography
Fulltext Observation of auditory perceptual and visuo-spatial characteristic of a patient with hemangiopericytoma in occipital lobe: a magnetoencephalography (MEG) study

Hanani Abdul Manan, Jafri Malin Abdullah, Zamzuri Idris, Mohammed Faruque Reza, Muhammad Hafiz Hanaf

Jurnal Sains Kesihatan Malaysia, 2018;16(2):85-91.
MyJurnal

The present study discussed functional reorganization and alteration in respond to the slow-growing tumour,
hemangiopericytoma in the occipital cortex. Visual evoked field (VEF) and auditory evoked field (AEF) using
magnetoencephalography (MEG) was used to evaluate the source localization and brain activity. Results of VEF source
localization show a typical brain waves. Brain activity of the occipital lobe demonstrate low activation in the ipsilateral
to the tumour. However, result shows the activation on the contralateral hemisphere was high and bigger in activation
volume. AEF result shows an identical source localization and both side of the temporal lobe are activated. This result
suggests that there is a positive plasticity in auditory cortex and slow-growing tumour can induce functional reorganization
and alteration to the brain.

Matched MeSH terms: Magnetoencephalography
Fulltext Magnetoencephalography Phantom Comparison and Validation: Hospital Universiti Sains Malaysia (HUSM) Requisite

Omar H, Ahmad AL, Hayashi N, Idris Z, Abdullah JM

Malays J Med Sci, 2015 Dec;22(Spec Issue):20-8.
PMID: 27006634 MyJurnal

Magnetoencephalography (MEG) has been extensively used to measure small-scale neuronal brain activity. Although it is widely acknowledged as a sensitive tool for deciphering brain activity and source localisation, the accuracy of the MEG system must be critically evaluated. Typically, on-site calibration with the provided phantom (Local phantom) is used. However, this method is still questionable due to the uncertainty that may originate from the phantom itself. Ideally, the validation of MEG data measurements would require cross-site comparability.

Matched MeSH terms: Magnetoencephalography
Observation of tumour-induced reorganization in structural and functional architecture of the brain in three pre-surgical patients with left frontal-temporal brain tumour: a combination of MEG, DTI and neuropsychological assessment

Hanani Abdul Manan, Zamzuri Idris, Jafri Malin Abdullah, Mohammed Faruque Reza, Wan Nor Azlen Wan Mohamad

Sains Malaysiana, 2017;46:1877-1886.

Visual function is mainly located within the bilateral hemisphere of the occipital lobes of the brain. However, our functional magnetoencephalography (MEG) result has demonstrated the reorganization of brain activity in the occipital area in patients with left-sided brain tumour. The results showed that brain laterality changes from bilateral to unilateral activation of the occipital area. Right occipital area (contralateral areas to the tumour), shows increase intensity of activation. Diffusion tensor imaging (DTI) with fibre tracking was performed to further investigate this brain laterality modification and the findings confirmed there is an alteration in the left hemisphere fibre optic tracts. This functional modification and changes of the brain laterality and optic tracts in the brain is suspected to be the result of tumour growth induced changes. The present observation will be discussed in term of the mechanism of tumour induced reorganization and changes with the corroborating evidence from MEG, DTI and neuropsychological assessment.

Matched MeSH terms: Magnetoencephalography
Fulltext Language Mapping in Awake Surgery: Report of Two Cases with Review of Language Networks

Lim LH, Idris Z, Reza F, Wan Hassan WMN, Mukmin LA, Abdullah JM

Asian J Neurosurg, 2018 4 24;13(2):507-513.
PMID: 29682074 DOI: 10.4103/ajns.AJNS_176_16

The role of language in communication plays a crucial role in human development and function. In patients who have a surgical lesion at the functional language areas, surgery should be intricately planned to avoid incurring further morbidity. This normally requires extensive functional and anatomical mappings of the brain to identify regions that are involved in language processing and production. In our case report, regions of the brain that are important for language functions were studied before surgery by employing (a) extraoperative methods such as functional magnetic resonance imaging, transmagnetic stimulation, and magnetoencephalography; (b) during the surgery by utilizing intraoperative awake surgical methods such as an intraoperative electrical stimulation; and (c) a two-stage surgery, in which electrical stimulation and first mapping are made thoroughly in the ward before second remapping during surgery. The extraoperative methods before surgery can guide the neurosurgeon to localize the functional language regions and tracts preoperatively. This will be confirmed using single-stage intraoperative electrical brain stimulation during surgery or a two-stage electrical brain stimulation before and during surgery. Here, we describe two cases in whom one has a superficial lesion and another a deep-seated lesion at language-related regions, in which language mapping was done to preserve its function. Additional review on the neuroanatomy of language regions, language network, and its impairment was also described.

Matched MeSH terms: Magnetoencephalography
Bayesian Algorithm Based Localization of EEG Recorded Electromagnetic Brain Activity

Jatoi MA, Kamel N, Musavi SHA, López JD

Curr Med Imaging Rev, 2019;15(2):184-193.
PMID: 31975664 DOI: 10.2174/1573405613666170629112918

BACKGROUND: Electrical signals are generated inside human brain due to any mental or physical task. This causes activation of several sources inside brain which are localized using various optimization algorithms.
METHODS: Such activity is recorded through various neuroimaging techniques like fMRI, EEG, MEG etc. EEG signals based localization is termed as EEG source localization. The source localization problem is defined by two complementary problems; the forward problem and the inverse problem. The forward problem involves the modeling how the electromagnetic sources cause measurement in sensor space, while the inverse problem refers to the estimation of the sources (causes) from observed data (consequences). Usually, this inverse problem is ill-posed. In other words, there are many solutions to the inverse problem that explains the same data. This ill-posed problem can be finessed by using prior information within a Bayesian framework. This research work discusses source reconstruction for EEG data using a Bayesian framework. In particular, MSP, LORETA and MNE are compared.
RESULTS: The results are compared in terms of variational free energy approximation to model evidence and in terms of variance accounted for in the sensor space. The results are taken for real time EEG data and synthetically generated EEG data at an SNR level of 10dB.
CONCLUSION: In brief, it was seen that MSP has the highest evidence and lowest localization error when compared to classical models. Furthermore, the plausibility and consistency of the source reconstruction speaks to the ability of MSP technique to localize active brain sources.

Matched MeSH terms: Magnetoencephalography/methods*
Fulltext Cortical spreading depression during repeated stimulation - a magnetoencephalographic study

Begum, T., Reza, F., Abdullah, J.M.

ASM Science Journal, 2011;5(2):115-121.
MyJurnal

Reflex epilepsy is usually induced by external stimulation, photosensitive epilepsy being the most common. Epilepsy induced by auditory stimulation is rarely studied. There are no currently published magnetoencephalographic (MEG) studies demonstrating the initiation of epileptic neuronal discharges by repeated auditory stimulations in temporal lobe epilepsy (TLE) patients. We retrospectively studied one TLE patient who underwent a MEG study to localize her epileptic focus. Auditory, somatosensory, visual and motor evoked potential studies were performed during the MEG recording. A single dipole method calculated equivalent current dipoles to localize the epileptic source. The least-squares minimization method was used to obtain the optimal solution with goodness-of-fit of greater than 80%. Periodic lateralized epileptiform discharges (PLEDs) were recorded in the temporal region when repeated auditory stimulations were done. We postulated that neuronal cortical suppression occurred during repeated stimulations which provoked epileptiform discharges (PLEDs) without any physical symptoms or aura. It was concluded that repeated stimulations could facilitate epileptiform discharges in focal area/areas in certain subjects.

Matched MeSH terms: Magnetoencephalography
Fulltext Neural oscillation, network, eloquent cortex and epileptogenic zone revealed by magnetoencephalography and awake craniotomy

Idris Z, Kandasamy R, Reza F, Abdullah JM

Asian J Neurosurg, 2014 Jul-Sep;9(3):144-52.
PMID: 25685205 DOI: 10.4103/1793-5482.142734

BACKGROUND: Magnetoencephalography (MEG) is a method of functional neuroimaging. The concomitant use of MEG and electrocorticography has been found to be useful in elucidating neural oscillation and network, and to localize epileptogenic zone and functional cortex. We describe our early experience using MEG in neurosurgical patients, emphasizing on its impact on patient management as well as the enrichment of our knowledge in neurosciences.
MATERIALS AND METHODS: A total of 10 subjects were included; five patients had intraaxial tumors, one with an extraaxial tumor and brain compression, two with arteriovenous malformations, one with cerebral peduncle hemorrhage and one with sensorimotor cortical dysplasia. All patients underwent evoked and spontaneous MEG recordings. MEG data was processed at band-pass filtering frequency of between 0.1 and 300 Hz with a sampling rate of 1 kHz. MEG source localization was performed using either overdetermined equivalent current dipoles or underdetermined inversed solution. Neuromag collection of events software was used to study brain network and epileptogenic zone. The studied data were analyzed for neural oscillation in three patients; brain network and clinical manifestation in five patients; and for the location of epileptogenic zone and eloquent cortex in two patients.
RESULTS: We elucidated neural oscillation in three patients. One demonstrated oscillatory phenomenon on stimulation of the motor-cortex during awake surgery, and two had improvement in neural oscillatory parameters after surgery. Brain networks corresponding to clinico-anatomical relationships were depicted in five patients, and two networks were illustrated here. Finally, we demonstrated epilepsy cases in which MEG data was found to be useful in localizing the epileptogenic zones and functional cortices.
CONCLUSION: The application of MEG while enhancing our knowledge in neurosciences also has a useful role in epilepsy and awake surgery.
KEYWORDS: Awake craniotomy; brain network; epilepsy; magnetoencephalography; neural oscillation

Matched MeSH terms: Magnetoencephalography
Decoding of visual information from human brain activity: A review of fMRI and EEG studies

Zafar R, Malik AS, Kamel N, Dass SC, Abdullah JM, Reza F, et al.

J Integr Neurosci, 2015 Jun;14(2):155-68.
PMID: 25939499 DOI: 10.1142/S0219635215500089

Brain is the command center for the body and contains a lot of information which can be extracted by using different non-invasive techniques. Electroencephalography (EEG), Magnetoencephalography (MEG) and functional magnetic resonance imaging (fMRI) are the most common neuroimaging techniques to elicit brain behavior. By using these techniques different activity patterns can be measured within the brain to decode the content of mental processes especially the visual and auditory content. This paper discusses the models and imaging techniques used in visual decoding to investigate the different conditions of brain along with recent advancements in brain decoding. This paper concludes that it's not possible to extract all the information from the brain, however careful experimentation, interpretation and powerful statistical tools can be used with the neuroimaging techniques for better results.

Matched MeSH terms: Magnetoencephalography

Filters

Please provide feedback to Administrator ([email protected])

External Links