Publications by authors named "Lydia Yahia Cherif"

Following the recent deployment of fifth-generation (5G) radio frequencies, several questions about their health impacts have been raised. Due to the lack of experimental research on this subject, the current study aimed to investigate the bio-physiological effects of a generated 3.5 GHz frequency.

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Introduction: Gait disorders and falls occur early in progressive supranuclear palsy (PSP-RS) and Caribbean atypical parkinsonism (Caribbean AP). However, the link between these signs and brain lesions has never been explored in these patient populations. Here, we investigate and compare the imaging factors that relate to gait and balance disorders in Caribbean AP and PSP-RS patients.

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Purpose: Wireless communication has become an integral part of our lives. The growing number of antennas in our environment and the expanding use of mobile phones (MPs) are increasing the population's exposure to electromagnetic fields. The present study aimed to examine the potential impact of MPs radiofrequency electromagnetic fields (RF-EMF) exposure on the brainwaves of the resting electroencephalogram (EEG) in humans.

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Background: Parkinson's disease (PD) demonstrates neurodegenerative changes in the substantia nigra pars compacta (SNc) using neuromelanin-sensitive (NM)-MRI. As SNc manual segmentation is prone to substantial inter-individual variability across raters, development of a robust automatic segmentation framework is necessary to facilitate nigral neuromelanin quantification. Artificial intelligence (AI) is gaining traction in the neuroimaging community for automated brain region segmentation tasks using MRI.

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Background The time course of cellular damage after acute ischemic stroke (IS) is currently not well known, and specific noninvasive markers of microstructural alterations linked to inflammation are lacking, which hinders the monitoring of anti-inflammatory treatment. Purpose To evaluate the temporal pattern of neuronal and glial microstructural changes after stroke using in vivo single-voxel diffusion-weighted MR spectroscopy. Materials and Methods In this prospective longitudinal study, participants with IS and healthy volunteers (HVs) underwent MRI at 3.

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Article Synopsis
  • This study investigates how attentional networks affect conscious perception by using magnetoencephalography and analyzing the impact of different types of peripheral cues on the detection of visual stimuli.
  • Both valid nonpredictive and predictive cues enhance conscious detection compared to invalid cues, but only predictive cues encourage a more liberal reporting criterion and improve detection rates.
  • Enhanced activity in frontoparietal networks was linked to conscious perception following valid predictive cues, with distinct hemispheric involvement during different phases of attention, indicating how misdirected attention can hinder conscious processing.
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Background: Isolated REM sleep behavior disorder (iRBD) is considered a prodromal stage of parkinsonism. Neurodegenerative changes in the substantia nigra pars compacta (SNc) in parkinsonism can be detected using neuromelanin-sensitive MRI.

Objective: To investigate SNc neuromelanin changes in iRBD patients using fully automatic segmentation.

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Several studies reported changes in spontaneous electroencephalogram alpha band activity related to radiofrequency electromagnetic fields, but findings showed both an increase and a decrease of its spectral power or no effect. Here, we studied the alpha band modulation after 900 MHz mobile phone radiofrequency exposure and localized cortical regions involved in these changes, via a magnetoencephalography (MEG) protocol with healthy volunteers in a double-blind, randomized, counterbalanced crossover design. MEG was recorded during eyes open and eyes closed resting-state before and after radiofrequency exposure.

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Article Synopsis
  • The study aimed to investigate the effects of mobile phone radiofrequency exposure on brain activity, specifically focusing on changes in the alpha band power spectral density (PSD) during resting-state EEG recordings.
  • Twenty-one healthy volunteers participated in a controlled experiment that included both sham and real mobile phone exposure while their brain activity was monitored in eyes-open and eyes-closed states.
  • Results indicated trends of increasing or decreasing alpha oscillation power during exposure, but these changes were not statistically significant, nor was there any evidence of varying sensitivity among individuals based on their alpha band frequency.
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  • The study investigated the effects of neurofeedback training (NFT) on brain activity, specifically focusing on alpha EEG activity, using a double-blind, sham-controlled design with 48 healthy participants divided into NFT and control groups.* -
  • Results showed a significant increase in alpha activity for the NFT group, while the control group exhibited no change, and no similar effects were found in other brain wave bands like theta and low beta.* -
  • Psychological outcomes indicated both groups experienced increased control, decreased anxiety, and enhanced relaxation, suggesting these effects may be attributed to learning context and placebo rather than direct effects of NFT.*
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  • Parkinson's disease leads to a decrease in dopamine function and an increase in iron in specific brain areas, particularly the substantia nigra, indicating potential interconnections between dopamine impairment and iron metabolism changes.
  • A study followed patients with early Parkinson's and REM sleep behavior disorder, using advanced imaging techniques to track levels of neuromelanin, iron, and dopamine over two years.
  • Results indicated that changes in dopamine levels occurred first in the sensorimotor regions, followed by alterations in iron metabolism and finally changes in neuromelanin, reflecting a typical progression pattern of the disease.
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Background: Development of reliable and accurate imaging biomarkers of dopaminergic cell neurodegeneration is necessary to facilitate therapeutic drug trials in Parkinson's disease (PD). Neuromelanin-sensitive MRI techniques have been effective in detecting neurodegeneration in the substantia nigra pars compacta (SNpc). The objective of the current study was to investigate longitudinal neuromelanin signal changes in the SNpc in PD patients.

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Freezing of gait is a challenging sign of Parkinson's disease associated with disease severity and progression and involving the mesencephalic locomotor region. No predictive factor of freezing has been reported so far. The primary objective of this study was to identify predictors of freezing occurrence at 5 years.

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Objectives: The classic Braak neuropathologic staging model in Parkinson disease (PD) suggests that brain lesions progress from the medulla oblongata to the cortex. An alternative model in which neurodegeneration first occurs in the cortex has also been proposed. These 2 models may correspond to different patient phenotypes.

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Background: Machine learning algorithms using magnetic resonance imaging (MRI) data can accurately discriminate parkinsonian syndromes. Validation in patients recruited in routine clinical practice is missing.

Objective: The aim of this study was to assess the accuracy of a machine learning algorithm trained on a research cohort and tested on an independent clinical replication cohort for the categorization of parkinsonian syndromes.

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This study aimed to investigate the spatiotemporal changes in neuromelanin-sensitive MRI signal in the substantia nigra and their relation to clinical scores of disease severity in patients with early or progressing Parkinson's disease and patients with idiopathic rapid eye movement sleep behaviour disorder (iRBD) exempt of Parkinsonian signs compared to healthy control subjects. Longitudinal T1-weighted anatomical and neuromelanin-sensitive MRI was performed in two cohorts, including patients with iRBD, patients with early or progressing Parkinson's disease, and control subjects. Based on the aligned substantia nigra segmentations using a study-specific brain anatomical template, parametric maps of the probability of a voxel belonging to the substantia nigra were calculated for patients with various degrees of disease severity and controls.

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Parkinson's disease (PD) is a progressive neurodegenerative disease whose main neuropathological feature is the loss of dopaminergic neurons of the substantia nigra (SN). There is also an increase in iron content in the SN in postmortem and imaging studies using iron-sensitive MRI techniques. However, MRI results are variable across studies.

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Diffusion-weighted (DW-) MRS investigates non-invasively microstructural properties of tissue by probing metabolite diffusion in vivo. Despite the growing interest in DW-MRS for clinical applications, little has been published on the reproducibility of this technique. In this study, we explored the optimization of a single-voxel DW-semi-LASER sequence for clinical applications at 3 T, and evaluated the reproducibility of the method under different experimental conditions.

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Background: Progressive supranuclear palsy (PSP) is a neurodegenerative clinically heterogeneous disorder, formal diagnosis being based on postmortem histological brain examination.

Objective: We aimed to perform a precise in vivo staging of neurodegeneration in PSP using quantitative multimodal MRI. The ability of MRI biomarkers to differentiate PSP from PD was also evaluated.

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Some individuals are reporting being sensitive to electromagnetic fields. They report some unspecific symptoms like headeache, sleep disruption, heart palpitations, itching, etc. The lack of scientific objective links between EHS symptoms and EMF exposure renders the diagnosis of EHS more complex.

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Background: Cognitive deficits in Parkinson's disease (PD) may result from damage in the cortex as well as in the dopaminergic, noradrenergic, and cholinergic inputs to the cortex. Cholinergic inputs to the cortex mainly originate from the basal forebrain and are clustered in several regions, called Ch1 to Ch4, that project to the hippocampus (Ch1-2), the olfactory bulb (Ch3), and the cortex and amygdala (Ch4).

Objective: We investigated changes in basal forebrain and their role in cognitive deficits in PD.

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Other's eye gaze is a powerful attention orienting cue that can change our perception of objects in the environment. Here, we seek to characterize the influence of attention orienting by eye gaze on the neural processing of visual targets. We used a Posner-like cueing paradigm to investigate with magnetoencephalography the brain responses associated with target processing.

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Objectives: Idiopathic rapid eye movement sleep behavior disorder (iRBD) is considered to be a prodromal stage of Parkinson's disease (PD). At PD onset, 40 to 70% of the dopaminergic neurons in the substantia nigra (SN) are already lost. Thus, milder SN damage is expected in participants with iRBD.

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Background: The objective of this study was to investigate pedunculopontine nucleus network dysfunctions that mediate impaired postural control and sleep disorder in Parkinson's disease.

Methods: We examined (1) Parkinson's disease patients with impaired postural control and rapid eye movement sleep behavior disorder (further abbreviated as sleep disorder), (2) Parkinson's disease patients with sleep disorder only, (3) Parkinson's disease patients with neither impaired postural control nor sleep disorder, and (4) healthy volunteers. We assessed postural control with clinical scores and biomechanical recordings during gait initiation.

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Objective: To describe the relation between gaze and posture/gait control in Parkinson disease (PD) and to determine the role of the mesencephalic locomotor region (MLR) and cortex-MLR connection in saccadic behavior because this structure is a major area involved in both gait/postural control and gaze control networks.

Methods: We recruited 30 patients with PD with or without altered postural control and 25 age-matched healthy controls (HCs). We assessed gait, balance, and neuropsychological status and separately recorded gait initiation and eye movements (visually guided saccades and volitional antisaccades).

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