Biology subjects

Liberati, G.

Publications and source records attributed to Liberati, G..

3 recordsLinked to original sources

bioRxiv2026

Posterior insula oscillations are not modulated by changes in perceived intensity: Evidence from human intracerebral EEG

The human insular cortex is involved in a multitude of processes essential for survival, but its precise role in pain perception remains debated. While it has been shown that ongoing oscillatory activity in the posterior insula is preferentially modulated by thermonociceptive input, it is unclear whether these modulations are functionally related to changes in pain perception. To assess this link, neural responses to sustained periodic thermonociceptive and non-nociceptive vibrotactile stimulation delivered at a frequency of 0.2 Hz were measured using intracerebral electrode contacts located in the anterior (n=63) and posterior (n=37) insular cortices of 10 patients undergoing presurgical evaluation for focal epilepsy. An arithmetic task was employed concomitant to the stimulation, aiming to reduce participants perceived intensity while leaving the physical stimulation parameters unchanged. A frequency-tagging analysis approach was used to assess the modulation of the ongoing neural oscillations. As expected, the perception of the stimulation was significantly reduced during the arithmetic task to a similar extent in both modalities. Yet, no congruent reduction in the frequency-tagged oscillatory responses was found in the posterior insula during distraction, for either of the modalities. On the contrary, during distraction, vibrotactile stimulation elicited larger responses in the anterior insula. These findings suggest that top-down modulation via distraction differentially affects anterior insula responses to innocuous vibrotactile input, while thermonociceptive processing appears to involve additional neural systems during distraction that are not equivalently engaged by vibrotactile stimulation.

neuroscience↗

bioRxiv2025

EEG frequency-tagging captures the neural integration of bilateral periodic thermonociceptive stimulation

Sustained periodic stimuli are known to elicit a periodic neural response (i.e. steady-state evoked potential) in the EEG frequency spectrum. These responses can easily be traced at their frequency of stimulation and corresponding harmonics using a frequency-tagging approach. To date, sustained periodic thermonociceptive stimuli have only been used on one extremity (e.g. right volar forearm) at a time. Extending this procedure to sustained stimulation applied concomitantly to distinct limbs would allow us to study the mechanisms of integration or competition between sensory signals from these different body locations. This study demonstrates that slow, sustained, sinusoidal thermonociceptive stimuli, bilaterally applied using two different stimulation frequencies (i.e. f1, f2, one on each forearm), elicit two distinct neural periodic responses at the respective frequency of stimulation and their harmonics. Additionally, we showed preliminary evidence for an interaction between the neural populations involved in the response to these stimuli, marked by neural activity at intermodulation frequencies (n* f1 {+/-} m* f2). So far, this non-linear integration of sensory information has already been observed following visual and auditory stimuli but not yet following thermonociceptive stimuli. New and noteworthyThis study demonstrates that sustained, slow, sinusoidal thermonociceptive stimulation applied simultaneously to both forearms at different frequencies elicits distinct neural responses at each stimulation frequency and its harmonics. Moreover, we provide preliminary evidence for interaction between the neural populations involved in the response to these stimuli during bilateral thermonociceptive stimulation. These findings extend frequency-tagging approaches in pain research and reveal potential non-linear sensory integration of distinct thermo-nociceptive inputs.

neuroscience↗

bioRxiv2025

Individualized Alpha-tACS for Modulating Pain Perception and Neural Oscillations: A Sham-Controlled Study in Healthy Participants

Pain encompasses sensory, affective, and cognitive dimensions, with neural oscillations increasingly recognized as key mechanisms in their integration. However, the underlying processes remain inadequately understood. Transcranial alternating current stimulation (tACS) offers a promising tool for modulating these oscillations, yet the widespread reliance on one-size-fits-all tACS protocols with fixed frequencies has led to limited and contradictory findings on its efficacy in pain treatment. In this study, we employed individualized tACS at individual peak alpha frequency (IAF) over the primary motor cortex (M1) contralateral to the dominant arm of 38 healthy participants, in a within-subject, sham-controlled design, to investigate its effects on pain perception and neural oscillations. Sustained and periodic 0.2 Hz thermonociceptive stimuli were applied to the dominant forearm before and after tACS. We measured participants pain perception and heat pain thresholds (HPT) before and after tACS stimulation. Scalp electroencephalography (EEG) measurements were used to measure neural activity during thermonociceptive stimuli. To calculate IAF, we used a discriminative approach based on independent component analysis (ICA) to separate sensorimotor related IAF (SM-IAF). The results revealed an overall increase in pain perception and a decrease in HPT in both sham and active conditions, with no significant interactions between conditions. However, a trend toward reduced sensitization post-tACS was observed. Exploratory analyses indicated a significant tACS effect on HPT in women. Furthermore, a significant correlation was found between SM-IAF and HPT. These findings provide a novel perspective on advancing individualized neuromodulation approaches for pain and neurobiological disorders.

neuroscience↗