Biology subjects

Medani, T.

Publications and source records attributed to Medani, T..

4 recordsLinked to original sources

bioRxiv2026

Microelectrode arrays enable directional stereo-EEG during kainate-mediated seizures

Surgical planning for drug-resistant epilepsy often relies on stereo-EEG (sEEG) recordings obtained with cylindrical ring electrodes. Prior modeling studies, including lead-field analysis, suggest that microelectrodes distributed around an sEEG-sized insulating body offer superior source amplification and directional sensitivity that are not available with either a ring design or microelectrodes on micro-structures, e.g. Neuropixel. However, these advantages have not been demonstrated in seizure models. This study evaluated high-density sEEG recordings using directional microelectrode arrays in a kainate-mediated rat model (n=6). Two 64-channel microelectrode arrays were implanted near the hippocampus, and the signals were spatially averaged to emulate virtual ring electrodes for comparison. Device locations were reconstructed and placed in copies of the Waxholm Space Rat Brain Atlas registered to subject-specific MRI scans. In subjects exhibiting seizures (n=4), automated line length detection showed that microelectrode signals identified epileptiform activity sooner and with greater specificity than ring electrodes. In subjects that only seized post-kainate injection (n=3), manual review by a board-certified epileptologist confirmed that microelectrodes provided the earliest onset detection times. Furthermore, the microelectrode arrays high resolution revealed distinct instances of hyperactivity occurring at similar depths but from different directions -- a feature indistinguishable to standard ring electrodes. These results demonstrate that microelectrodes on a large insulating body significantly enhance signal quality and spatial localization. This technology offers a potential advancement over current clinical standards for identifying seizure foci during surgical planning. SIGNIFICANCESurgical treatment for drug-resistant epilepsy depends on accurately identifying the brain regions where seizures begin. Current stereo-EEG electrodes sample activity with ring contacts that average signals around the probe shaft, potentially obscuring directional differences in nearby neural activity. This study shows that microelectrodes distributed around an sEEG-sized insulating body can improve seizure-related signal detection and spatial localization compared with ring-like recordings from the same implant locations. By resolving activity that conventional ring electrodes cannot distinguish, high-density directional sEEG may provide more informative recordings for seizure mapping. These findings support the development of next-generation intracranial electrodes for improving epilepsy surgical planning.

neuroscience↗

bioRxiv2025

sEEG-Suite: An Interactive Pipeline for Semi-Automated Contact Localization and Anatomical Labeling with Brainstorm

Stereoelectroencephalography (sEEG) is a critical tool for mapping epileptic networks in patients with drug-resistant epilepsy. Accurate localization and labeling of sEEG contacts are essential for identifying the seizure onset zone (SOZ) and ensuring optimal resective surgery. Traditional methods for localizing and labeling sEEG contacts rely on manual processing, which is prone to human error and variability. To address these challenges, we developed and integrated a semi-automatic sEEG contact localization and labeling pipeline within Brainstorm1, an open-source software platform for multimodal brain imaging analysis2-8, widely adopted in the neuroscience community with over 50,000 registered users and an active online user forum. The software has been supported by the National Institute of Health (NIH) for over two decades. The pipeline presented in this paper performs three key steps: (1) import and apply rigid co-registration of post-implantation Computed Tomography (CT) or post-CT with pre-implantation Magnetic Resonance Imaging (pre-MRI), (2) post-CT image segmentation and semi-automatic detection of sEEG contacts using GARDEL9, which has been integrated as a Brainstorm plugin, and (3) automatic anatomical labeling of contacts using standard and commonly used brain anatomy templates and atlases. Integrating this pipeline into Brainstorm brings the best of both worlds: GARDELs automation and Brainstorms multimodal data compatibility, and rich library of visualization and advanced analysis tools at both sensor and source level6. This sEEG-Suite tool facilitates reproducible research, supports clinical workflows, and accelerates sEEG-based investigations of invasive brain recordings.

neuroscience↗

bioRxiv2022

EEG-neurofeedback for promoting neuromodulation in the elderly: evidence from a double-blind study

BackgroundElectroencephalography (EEG) is a non-invasive method that records the brain signals with time resolution in the millisecond range, thereby allowing the monitoring of subjects mental states in real time. Using appropriate biomarkers extracted from these EEG signals and presenting them back in a neurofeedback loop can foster neural compensation mechanisms by teaching subjects to modulate their brain activity. Over the last decades, several neural biomarkers of aging have been described, with growing evidence suggesting that neuromodulation may have an important role in regulating brain activity in the elderly. Methods and objectivesWe used three neural biomarkers of aging, namely the Peak Alpha Frequency, the Gamma-band synchronization, and the Theta/Beta ratio, in the framework of an EEG-based brain-computer interface, with two main objectives: 1) to test whether healthy elderly people with subjective memory complaints may learn to modulate their brain activity through EEG-neurofeedback training in a double-blind, placebo-controlled study; and 2) whether that neuromodulation may have a positive impact on subjects cognition. ResultsA significant self-modulation of two neural biomarkers that usually decline with age was observed exclusively in the group of subjects who underwent the EEG-neurofeedback training, in clear contrast with the subjects who received the sham feedback. This neuromodulation did not have a direct effect on subjects cognitive abilities, as measured by neuropsychological tests pre-versus post-training, probably because all the subjects accurately performed these tests already at study entry (i.e., pre-training). ConclusionThe results of this double-blind study are in line with one of the main criteria for successful neuromodulation, thus encouraging research on EEG-neurofeedback as a promising non-pharmacological intervention for promoting self-regulation of brain activity with a view to improve cognitive aging.

neuroscience↗

bioRxiv2022

Why Are Alzheimer's Disease Patients Unaware of their Memory Deficits?

Anosognosia, or the lack of awareness of ones own impairment, is frequent for memory deficits in patients with Alzheimers disease (AD). Although often related to frontal dysfunctions, the neural mechanisms of anosognosia remain largely unknown. We hypothesized that anosognosia in AD may result from a failure in the error-monitoring system, thus preventing patients from being aware of and learning from their own errors. We therefore investigated the event-related potentials evoked by erroneous responses during a memory task in two groups of amyloid positive individuals who had only subjective memory complaints at study entry: 1) those who progressed to AD; and 2) those who remained cognitively normal after five years of follow-up. Our findings revealed direct evidence of a failure in the error-monitoring system at early stages of AD, suggesting that it may be the critical neural substrate of anosognosia in this neurodegenerative disorder.

neuroscience↗