ABSTRACT
@#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) usingmagnetoencephalography (MEG) was used to evaluate the source localization and brain activity. Results of VEF sourcelocalization show a typical brain waves. Brain activity of the occipital lobe demonstrate low activation in the ipsilateralto the tumour. However, result shows the activation on the contralateral hemisphere was high and bigger in activationvolume. AEF result shows an identical source localization and both side of the temporal lobe are activated. This resultsuggests that there is a positive plasticity in auditory cortex and slow-growing tumour can induce functional reorganizationand alteration to the brain.
ABSTRACT
@#Neuroplasticity has been subjected to a great deal of research in the last century. Recently, significant emphasis has beenplaced on the global effect of localized plastic changes throughout the central nervous system, and on how these changesintegrate in a pathological context. The present study aimed to demonstrate the functional cortical reorganization beforeand after surgery using magnetoencephalography (MEG) in a participant with brain tumor. Results of Visual EvokedMagnetic Field (VEF) based on functional MEG study revealed significantly different of MEG N100 waveforms before andafter surgery. Larger and additional new locations for visual activation areas after the surgery were found suggestingneuroplasticity. The present study highlight a physiological plasticity in a teenage brain and the alterations regardingneural plasticity and network remodeling described in pathological contexts in higher-order visual association areas.
ABSTRACT
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.
ABSTRACT
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.