Biology subjects

Jourahmad, Z.

Publications and source records attributed to Jourahmad, Z..

3 recordsLinked to original sources

bioRxiv2026

Electrophysiological features of signals recorded from white matter

Intracranial neurophysiology studies have typically ignored signals from electrodes located in white matter (WM), assuming that their information content is artifactual or related to nearby gray matter (GM). Here, we tested the electrophysiological and functional features of signals recorded from different WM locations. Signals were recorded from 19 patients undergoing intracranial monitoring for drug-resistant epilepsy by means of stereo-electroencephalography (sEEG). Each sEEG electrode was classified into WM or GM based on the surrounding tissue. We obtained recordings from a total of 1,717 sEEG electrode contacts, 36% in WM, while the patients were in awake resting state (5 minutes). For each sEEG electrode, we employed a model-based spectral decomposition to separate periodic and aperiodic components, and we computed signal complexity metrics. For a subset of participants, we computed WM structural information from diffusion-weighted magnetic resonance imaging and we evaluated functional signals during a cognitive control task. Our results show that signals recorded from WM have different spectral features and higher complexity than GM. Complexity correlates positively with fractional anisotropy, and modulations related to behavior during the task were detected in WM. Overall, this indicates that WM signals carry information that may reflect signal propagation across WM fiber tracts.

neuroscience↗

bioRxiv2025

Distinct Temporal Patterns of Human Neural Firing in the Subthalamic Nucleus During Speech and Orofacial Movement

Clinical studies, along with electrophysiological findings, provide evidence that the subthalamic nucleus (STN) contributes to speech production. These studies have reported that the STN encodes diverse aspects of speech, comprising speech motor planning and execution, timing, and linguistic features such as phonetic content. However, none of these studies have included an orofacial non-speech motor task to evaluate speech-specificity of STN activity. Here, we examined the modulation of STN neurons while participants engaged in two speech tasks (sentence repetition and syllable repetition) as well as two non-speech orofacial movement tasks (jaw movement and tongue protrusion) in awake patients with Parkinsons disease undergoing deep brain stimulation implantation surgery. A total of 51 single- and multi-unit neural clusters were captured. A Poisson generalized linear model (GLM) was implemented to understand the temporal dynamics of STN activity. A larger proportion of clusters was modulated during speech (22%) than during orofacial movement (12%) and a substantial subset of STN neural clusters responded to overlapping speech and orofacial tasks (27%). The findings suggest that STN can encode both motor and linguistic aspects of speech production. Graphical abstractThe subthalamic nucleus (STN) shows neural modulation during speech production, a process which requires motor planning, execution, and phonological functions. By comparing STN spiking activity during speech tasks (sentence and syllable repetition) and non-speech orofacial tasks (jaw movement and tongue protrusion), we identified task-specific modulation patterns in STN neurons. The STN contains distinct neural populations engaged during speech and orofacial movements. Among all recorded clusters, 22% responded exclusively to speech, 12% exclusively to orofacial movements, 27% to both, and 39% were non-responsive. We demonstrated that STN activity at single- and multi-unit levels is specific to speech production and is influenced by task-specific motor and linguistic demands, highlighting a role for STN in integrating motor control and speech production. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=108 SRC="FIGDIR/small/693637v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@1ec3c60org.highwire.dtl.DTLVardef@6fe46forg.highwire.dtl.DTLVardef@1fe733corg.highwire.dtl.DTLVardef@3f736b_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2025

Human neuronal firing is modulated by the frequency of local field potential oscillations

Neural oscillations play a critical role in shaping neuronal firing patterns. While phase-locked neuronal firing ("phase tuning") has been extensively studied in animal models and human invasive recordings, much less is known about whether neurons show preferential firing at specific oscillatory frequencies, termed frequency tuning. Here, we employ human intracranial recordings across several brain regions including hippocampus, entorhinal cortex, anterior and posterior cingulate cortex, and orbitofrontal cortex to test the hypothesis that neurons exhibit frequency-specific firing. We analyzed 357 single units recorded simultaneously with local field potentials in 19 neurosurgical patients during awake resting. We estimated the instantaneous frequency of the LFP using adaptive spectral decomposition and assessed frequency tuning of each neuron while controlling for changes in firing rate unrelated to frequency changes. We found 27% neurons exhibited increased or decreased firing within specific frequencies, most commonly within the low-theta range (<10 Hz). Neurons exhibiting frequency tuning were distinct from those displaying phase tuning, and both types of tuning were observed across multiple brain regions with no anatomical preference. Together, our results demonstrate that the instantaneous frequency of neural oscillations modulates neuronal firing which may serve as an additional mechanism for information processing in the human brain, opening new avenues for frequency-targeted neural stimulation.

neuroscience↗