Biology subjects

Gaugain, G.

Publications and source records attributed to Gaugain, G..

5 recordsLinked to original sources

bioRxiv2026

Computational Insights into the tACS Modulation in Healthy and Epileptic Brain Networks

Transcranial Electric stimulation (tES) is a safe and noninvasive technique increasingly used in treating brain disorders. Despite many studies on tES, there is still a lack of understanding of its mechanisms at the microscale network level. This is crucial for optimized parameter selection in therapy approaches such as the treatment of pharmacoresistant epilepsy. In this study, we made use of a recently published neuroinspired microscale model of the neocortex, known as NeoCoMM, and integrated a "Lambda E"-based model of tES. This updated version was used to investigate the acute effects of tES (tDCS and tACS), on the neural activity of various neuron types in both healthy and epileptic brain states. Results showed that in the case of healthy alpha and gamma rhythms, tACS induced electric field entrainment at the peak power frequency of the network oscillations as measured by the Local field Potentials (LFPs). This resonance-like entrainment was independent from the individual firing rate of cell types. For epileptic activity, tACS did not provide consistent results. Cathodal tDCS resulted in a promising decrease in hyperexcitable activity throughout simulations. These results advance our understanding of the impact of tES on network dynamics at both the extracellular and intracellular activity levels. Author summary

neuroscience↗

bioRxiv2025

Accurate evaluation of neural sensitivity to weak alternating electric fields requires protocols accounting for input dependence

Background: Weak alternating electric fields ([~]1 V/m) modulate nervous system activity. Yet, the exact mechanism by which such low amplitude electric fields can modulate neural activity is still unknown despite the use of specific protocols aiming at quantifying neural sensitivity. Objective: To characterize how the measurement protocol can impact neural sensitivity to weak electric fields and bias in vivo sensitivity. Methods: We considered a variety of somatic clamp stimulation to drive the activity of biophysical morpho-realistic reconstructed neurons during extracellular alternating stimulation to quantify the sensitivity to the field depending on the nature of cells activity. Results: Cells sensitivity to alternating current stimulation depended on the type of input used to drive their activity, with a different frequency response for each protocol, with a trend for inhibitory neurons to be more sensitive to higher stimulation frequencies. Even with the same clamp protocol, sensitivity depended on the statistics of the input used. Significance: Neuronal sensitivity to alternating current stimulation is highly input-dependent, which has been largely neglected so far, and depends on the current statistic of the received inputs, and is not reliably represented by simple current clamps protocols.

neuroscience↗

bioRxiv2025

1.4 GHz amplitude-modulated radiofrequency electromagnetic waves effects on neural cultures

Non-invasive brain stimulation (NIBS) technologies have the potential to positively impact the treatment of neurological disorders. However, NIBS techniques suffer from a lack of penetration depth and focality, thereby restraining their full potential. Here, we investigate the feasibility of a novel technique based on sinusoidal radiofrequency electromagnetic fields (RF-EMF) that are amplitude-modulated in the extremely low frequency (ELF) range. To assess the neuromodulatory effects of ELF-modulated RF-EMF, we exposed primary neuronal cultures placed on Multi-Electrode Arrays (MEAs) and quantified their spiking activity based on phase entrainment. Our results failed to reveal consistent phase entrainment across cultures, while replicating a decrease of neuronal activity with purely sinusoidal 1.4 GHz stimulation. Finally, we suggest protocol improvements that might result in more reproducible effects, which is indispensable for translational applications.

neuroscience↗

bioRxiv2023

Frequency-dependent phase entrainment of cortical cell types during tACS: Converging modeling evidence

BackgroundTranscranial alternating current stimulation (tACS) enables non-invasive modulation of brain activity, holding promise for clinical and research applications. Yet, it remains unclear how the stimulation frequency affects various neuron types. ObjectiveTo quantify the frequency-dependent behavior of key neocortical cell types. MethodsWe used both detailed (anatomical multicompartments) and simplified (three compartments) single-cell modeling approaches based on the Hodgkin-Huxley formalism to study neocortical excitatory and inhibitory cells under various-amplitude tACS frequencies within the 5-50 Hz range at rest and during basal 10 Hz activity. ResultsL5 pyramidal cells exhibited the highest polarizability at DC, ranging from 0.21 to 0.25mm and decaying exponentially with frequency. Inhibitory neurons displayed membrane resonance in the 5-15 Hz range with lower polarizability, although bipolar cells had higher polarizability. Layer 5 PC demonstrated the highest entrainment close to 10 Hz, which decayed with frequency. In contrast, inhibitory neurons entrainment increased with frequency, reaching level akin to PC. Results from simplified models could replicate the phase preferences, while amplitudes tend to follow opposite trends in PC. ConclusiontACS-induced membrane polarization is frequency-dependent, revealing observable resonance behavior. This finding motivates further experimental studies of cell-specific frequency-dependent membrane responses to weak electric stimuli. Whilst optimal phase entrainment of sustained activity is achieved in PC when tACS frequency matches the activity, inhibitory neurons tend to be entrained at higher frequencies. Consequently, this presents the potential for precise, cell-specific targeting. O_LISingle-cell models of frequency response to tACS for a wide variety of neurons C_LIO_LISimplified and morphologically accurate models were compared C_LIO_LIPyramidal cells (PC) show resonant-like response close to intrinsic firing frequency C_LIO_LIEntrainement of GABAergic neurons increases with the frequency of tACS C_LIO_LIMembrane polarization resonance in GABAergic neurons within the 5-15 Hz range C_LI

neuroscience↗

bioRxiv2021

The neural response to the temporal fine structure of continuous musical pieces is not affected by selective attention

Speech and music are spectro-temporally complex acoustic signals that a highly relevant for humans. Both contain a temporal fine structure that is encoded in the neural responses of subcortical and cortical processing centres. The subcortical response to the temporal fine structure of speech has recently been shown to be modulated by selective attention to one of two competing voices. Music similarly often consists of several simultaneous melodic lines, and a listener can selectively attend to a particular one at a time. However, the neural mechanisms that enable such selective attention remain largely enigmatic, not least since most investigations to date have focussed on short and simplified musical stimuli. Here we study the neural encoding of classical musical pieces in human volunteers, using scalp electroencephalography (EEG) recordings. We presented volunteers with continuous musical pieces composed of one or two instruments. In the latter case, the participants were asked to selectively attend to one of the two competing instruments and to perform a vibrato identification task. We used linear encoding and decoding models to relate the recorded EEG activity to the stimulus waveform. We show that we can measure neural responses to the temporal fine structure of melodic lines played by one single instrument, at the population level as well as for most individual subjects. The neural response peaks at a latency of 7.6 ms and is not measurable past 15 ms. When analysing the neural responses elicited by competing instruments, we find no evidence of attentional modulation. Our results show that, much like speech, the temporal fine structure of music is tracked by neural activity. In contrast to speech, however, this response appears unaffected by selective attention in the context of our experiment.

neuroscience↗