Papers by M. Mahmoudzadeh
Clinical Neurophysiology, 2016
NeuroImage: Clinical, 2015
ISRN Neuroscience, 2013
It is well established that the two hemispheres of the human brain exhibit a certain degree of as... more It is well established that the two hemispheres of the human brain exhibit a certain degree of asymmetry. Postmortem studies of developing brains of pre-and postpartum infants have shown that already in this early stage of development Heschl gyrus, planum temporale and superior temporal sulcus (STS) exhibit pronounced asymmetry. Advances in acquisition and computational evaluation of high-resolution magnetic resonance images provide enhanced tools for noninvasive studies of brain asymmetry in newborns. Until now most atlases used for image processing contain themselves asymmetry and may thus introduce and/or increase asymmetry already contained in the original data of brain structural or functional images. So, it is preferable to avoid the application of these asymmetric atlases. Thus, in this paper we present our framework to create a symmetric brain atlas from a group of newborns aged between 39 and 42 weeks after gestation. The resulting atlas demonstrates no difference between its original and its flipped version as should be the case for an asymmetric atlas. Consequently, the resulting symmetric atlas can be used for applications such as analysis of development of brain asymmetry in the context of language development.
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... J Pediatr 2004; 145: 832-4. [5] Roche-Labarbe, N., Ponchel, E., Kongolo, G., Grebe, R., and W... more ... J Pediatr 2004; 145: 832-4. [5] Roche-Labarbe, N., Ponchel, E., Kongolo, G., Grebe, R., and Wallois, F. Coupled oxygenation oscillations measured by NIRS and intermittent cerebral activation on EEG in premature infants. Neuroimage, 36, 718-727, 2007.
Radiology, 2012
To investigate patterns of whole-brain functional connectivity in patients with minimal hepatic e... more To investigate patterns of whole-brain functional connectivity in patients with minimal hepatic encephalopathy (HE) by using functional magnetic resonance (MR) imaging. This study was approved by the local institutional review board and was HIPAA compliant. All participants provided written informed consent. Neuropsychiatric tests including number connection test type A and digit symbol test were used to define minimal HE. Twenty-three patients with minimal HE and 25 age- and sex-matched healthy volunteers were included in this study. Resting-state functional MR imaging was performed by using a 3-T MR imaging unit. Functional connectivities between 90 pairs of cortical and subcortical regions in patients with minimal HE were compared with those in control participants, and significantly different connectivities were chosen as connectivities of interest (COIs). Correlations between neuropsychiatric tests and correlation coefficients of COIs were calculated. Among the 51 COIs that were significantly different in patients with minimal HE from those in control participants, 44 connectivities were weaker in patients with minimal HE. All 22 COIs related to subcortical regions of interest (bilateral putamen, pallidum, and thalamus) were weaker in patients with minimal HE. Of 29 cortical COIs, 22 connectivities were weaker and seven were stronger in patients with minimal HE. Nearly all COIs with significant differences correlated with digital symbol test scores (P<.05, false discovery rate corrected). No correlation was found among blood ammonia level, Child-Pugh scores, or any COIs in patients with minimal HE (P>.05, false discovery rate corrected). Widespread cortical and subcortical network connectivity changes that correlated with neuropsychologic impairment were found in patients with minimal HE. In particular, impairment in the basal ganglia-thalamocortical circuit could play an important role in mediating neurocognitive dysfunction, especially for psychomotor speed and attention deficits in patients with minimal HE.
Neurophysiologie Clinique/Clinical Neurophysiology, 2012
NeuroImage, 2009
141 SA-AM Effective connectivity of unilateral left or right mesial temporal lobe epilepsy during... more 141 SA-AM Effective connectivity of unilateral left or right mesial temporal lobe epilepsy during verbal memory task,
Clinical Neurophysiology, 2011
2013 21st Iranian Conference on Electrical Engineering (ICEE), 2013
Since the human brain has a certain degree of asymmetry, asymmetry analysis based on an asymmetri... more Since the human brain has a certain degree of asymmetry, asymmetry analysis based on an asymmetric brain template may result in ambiguity. Therefore, in this paper we present our framework to create a symmetric brain template from a group of newborns aged between 39 to 42 weeks after gestation. Consequently, the resulting template shows no difference between its original and its flipped version as is the case for an asymmetric template. The resulting symmetric template can be used e.g. for brain asymmetry analysis in language development.
Proceedings of the National Academy of Sciences, 2013
The ontogeny of linguistic functions in the human brain remains elusive. Although some auditory c... more The ontogeny of linguistic functions in the human brain remains elusive. Although some auditory capacities are described before term, whether and how such immature cortical circuits might process speech are unknown. Here we used functional optical imaging to evaluate the cerebral responses to syllables at the earliest age at which cortical responses to external stimuli can be recorded in humans (28-to 32-wk gestational age). At this age, the cortical organization in layers is not completed. Many neurons are still located in the subplate and in the process of migrating to their final location. Nevertheless, we observed several points of similarity with the adult linguistic network. First, whereas syllables elicited larger right than left responses, the posterior temporal region escaped this general pattern, showing faster and more sustained responses over the left than over the right hemisphere. Second, discrimination responses to a change of phoneme (ba vs. ga) and a change of human voice (male vs. female) were already present and involved inferior frontal areas, even in the youngest infants (29-wk gestational age). Third, whereas both types of changes elicited responses in the right frontal region, the left frontal region only reacted to a change of phoneme. These results demonstrate a sophisticated organization of perisylvian areas at the very onset of cortical circuitry, 3 mo before term. They emphasize the influence of innate factors on regions involved in linguistic processing and social communication in humans.
Neurophysiologie Clinique/Clinical Neurophysiology, 2012
Neurophysiologie Clinique/Clinical Neurophysiology, 2012
Brain and Language, 2012
One of the most challenging tasks in neuroscience in language studies, is investigation of the br... more One of the most challenging tasks in neuroscience in language studies, is investigation of the brain's ability to integrate and process information. This task can only be successfully addressed by applying various assessment techniques integrated into a multimodal approach. Each of these techniques has its advantages and disadvantages, but help to elucidate certain aspects of the capacity of neural networks to process information. These methods provide information about changes in electrical, hemodynamic and metabolic activities. Ideally, they should be noninvasive in order to facilitate their use particularly in children.
Clinical Neurophysiology, 2011
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Papers by M. Mahmoudzadeh