Biology subjects

Michalak, A. J.

Publications and source records attributed to Michalak, A. J..

3 recordsLinked to original sources

bioRxiv2025

Mithra: An Open-Source and Cross-Platform Visualization Toolbox for Human Intracranial Recordings

Intracranial electrophysiological recordings, including electrocorticography (ECoG) and stereo-EEG (sEEG), are increasingly used across research programs to study human brain function due to their high spatiotemporal resolution. Numerous tools exist for electrode localization and visualization; however, most focus on subject-level visualization and provide only partial solutions for systematic within- and across-subject analyses. It is especially important to preserve subject-specific anatomical locations while mapping electrodes to standardized spaces for analysis across multiple subjects. To address these needs, we present Mithra1: a toolkit for visualizing intracranial recordings, implemented in both Python and MATLAB. The toolbox enables visualization of electrodes alongside the brains pial surface and anatomical annotations, supports localization in common average spaces such as the MNI and FreeSurfer average brains, and maintains alignment with individual anatomy. It further allows electrode projection onto the cortical surface to generate Gaussian heatmaps representing the spatial distribution of neural activity. By integrating these capabilities into a unified framework, our toolbox provides a flexible, cross-platform solution for systematic within- and across-subject electrode visualization and analysis.

neuroscience↗

bioRxiv2025

A probabilistic functional atlas based on extraoperative electrocortical stimulation mapping

BackgroundDirect electrocortical stimulation (DES) is the clinical gold standard for identifying eloquent cortex and guiding neurosurgical intervention, yet prior intraoperative DES during awake craniotomies have been limited by intraoperative sampling constraints and density-based rather than probabilistic analyses. The probability of typical and atypical cortical organization has not been fully explored, especially in epilepsy populations. We sought to generate a probabilistic atlas of motor, sensory, and language functions using extraoperative DES in a large cohort of patients with epilepsy. MethodsWe retrospectively analyzed 2,124 extraoperative DES trials from 125 patients undergoing intracranial monitoring (2008-2023). Positive and negative trials were mapped to Montreal Neurological Institute space, parcellated with the Human Connectome Project atlas, and analyzed using probability mapping, bootstrapped region-of-interest hit probabilities, hierarchical clustering, and kernel density estimation. Mixed-effects models assessed clinical predictors of language disruption. ResultsProbabilistic maps revealed regions of increased likelihood for eliciting functional responses in expected sensorimotor and language territories, but also demonstrated marked variability and deviations from expected cortical locations. Language disruption occurred in 338 trials, motor in 520, and sensory in 370. Instead of observing high probabilities and low inter-patient variability isolated to classic perisylvian locations (e.g., Brocas and Wernickes areas), the likelihood of language disruption followed graded probabilistic gradients with high inter-patient variability. The middle frontal gyrus emerged as a consistent locus of naming and speech arrest. Motor phenomena extended into parietal association cortex. Higher-order experiences, including forced thoughts and feelings of presence, were reproducibly evoked from frontal and temporoparietal sites. Early seizure onset and temporal lobe lesions predicted lower naming disruption probabilities. ConclusionsThis extraoperative DES atlas, the largest to date, demonstrates that eloquent cortical functions are organized along probabilistic continua rather than fixed regions. Findings highlight the middle frontal gyrus as a critical language node, extend motor mapping into parietal cortex, and delineate reproducible experiential phenomena. Substantial inter-patient variability underscores the necessity of individualized mapping in surgical planning.

neuroscience↗

bioRxiv2024

Spectral-switching analysis reveals real-time neuronal network representations of concurrent spontaneous naturalistic behaviors in human brain

Despite abundant evidence of functional networks in the human brain, their neuronal underpinnings, and relationships to real-time behavior have been challenging to resolve. Analyzing brain-wide intracranial-EEG recordings with video monitoring, acquired in awake subjects during clinical epilepsy evaluation, we discovered the tendency of each brain region to switch back and forth between 2 distinct power spectral densities (PSDs 2-55Hz). We further recognized that this spectral switching occurs synchronously between distant sites, even between regions with differing baseline PSDs, revealing long-range functional networks that would be obscured in analysis of individual frequency bands. Moreover, the real-time PSD-switching dynamics of specific networks exhibited striking alignment with activities such as conversation and hand movements, revealing a multi-threaded functional network representation of concurrent naturalistic behaviors. Network structures and their relationships to behaviors were stable across days, but were altered during N3 sleep. Our results provide a new framework for understanding real-time, brain-wide neural-network dynamics.

neuroscience↗