The research, led by Giulia Mattavelli, Francesco Crottini, and Gerardo Salvato of the University of Pavia and Istituti Clinici Scientifici Maugeri, builds on a decade of intriguing but contested observations linking skin temperature to how we perceive our bodies. Earlier studies of the rubber hand illusion, in which synchronous stroking makes people adopt a fake hand as their own, reported cooling of the real limb, but later replications produced inconsistent results, likely because of differences in paradigms, measurement techniques, and how temperature changes were quantified. More robust effects emerged from the mirror box illusion, the paradigm used in the new study, in which participants tap the index fingers of both hands while viewing the reflection of their right hand in a mirror aligned with the body midline, leaving the left hand hidden from view. When the tapping is synchronous, many people come to feel that the reflected right hand is actually their concealed left hand, and their hands measurably cool.

Thirty-six healthy right-handed adults, aged 18 to 47, took part in the experiment. Each participant performed 100 tapping trials in a synchronous condition, where both index fingers moved toward and away from the mirrors simultaneously, and an asynchronous condition, where the fingers moved in opposite directions at the same tempo. Movement frequency and total movement count were matched, so only the visuomotor congruence differed between conditions. The setup created a deliberate conflict between what participants saw, a right hand reflected on the left side of space, and what they felt proprioceptively, a left hand hidden under a cloak. After each condition, participants rated how strongly the hand in the mirror felt like their left hand and verbally estimated the position of their hidden left index finger, while an infrared thermal camera captured the temperature of both hands before and after each block.

The illusion worked as expected. Synchronous stimulation produced significantly stronger agreement with the statement that the hand in the mirror felt like the participant’s left hand, with mean ownership ratings of 1.72 compared with minus 0.36 in the asynchronous condition. The perceived position of the hidden left index finger also drifted substantially toward the mirror after synchronous tapping, averaging nearly 47 millimeters of displacement versus about 11 millimeters after asynchronous tapping. Crucially, thermal imaging revealed a bilateral reduction in skin temperature following the synchronous condition, with an average decrease of 0.363 degrees Celsius compared with 0.155 degrees after asynchronous stimulation, a difference that was statistically significant for both hands. Within individual participants, larger temperature drops covaried with larger proprioceptive drift, directly tying the physiological change to the spatial recalibration of the body image.

The central novelty of the study lay in what happened in the brain during these manipulations. Using 64-channel EEG recordings and independent component analysis, the researchers identified a right-lateralized cluster of sources centered on premotor and supplementary motor areas and parietal cortex whose oscillatory activity differed between conditions in the theta to low-alpha range, roughly 4 to 9 hertz. Asynchronous tapping, which confronts the brain with a visuo-motor mismatch, produced stronger event-related desynchronization in this band around 300 milliseconds after movement onset, suggesting heightened engagement of sensorimotor circuits to process the sensory incongruence. Synchronous tapping, by contrast, was associated with greater inter-trial phase coherence around 400 milliseconds, indicating more consistent timing of neural responses when the multisensory signal was coherent and integrated.

When the researchers correlated the power in this 4-to-9-hertz band with the temperature changes measured by thermal imaging, a striking pattern emerged: within the same participant, increases in theta/low-alpha power during the illusion covaried with larger reductions in skin temperature, a significant repeated-measures correlation. Notably, the oscillatory power did not correlate with the subjective vividness of the illusion or with proprioceptive drift. This dissociation, the authors argue, fits the view that body ownership is not a single unified representation but an emergent construct supported by distributed neural systems that handle partially distinct aspects of bodily self-representation, with thermoregulatory signals coupled to the sensorimotor layer rather than to conscious ratings alone.

To probe whether these local oscillations were embedded in larger-scale communication, the team reconstructed activity at the cortical source level and computed functional connectivity using the debiased weighted phase lag index, a metric that quantifies phase synchronization while minimizing artifacts from volume conduction. Clustering the significant connections revealed six distinct connectivity patterns induced by the illusion. One of them, a distributed frontoparietal-insular network linking bilateral sensorimotor cortices, superior parietal regions, the right supramarginal gyrus, and the left anterior insula and operculum, was directly associated with temperature: stronger connectivity within this module in the theta/low-alpha band predicted greater subsequent drops in hand temperature. The insula’s involvement is particularly telling, since it is a well-established hub for thermosensory processing, receiving spinothalamic input about cutaneous temperature and integrating it with interoceptive and emotional states.

The network identified in healthy brains bears a remarkable resemblance to the circuitry disrupted in clinical conditions. In an earlier study by the same group, stroke patients with disturbed sensation of limb ownership showed reduced limb temperature alongside lesions involving the right insula and disconnection between bilateral parietal hubs, including the primary and secondary somatosensory cortices and the inferior parietal gyrus. Abnormal temperature patterns have also been documented in complex regional pain syndrome, body integrity dysphoria, and anorexia nervosa, all conditions in which bodily self-awareness is disturbed. The convergence between network-level dynamics in healthy participants and patterns of disconnection in patients suggests, the authors contend, that thermosensory signals constitute a fundamental component of the neural architecture supporting bodily self-awareness rather than an epiphenomenal consequence of ownership changes.

The findings also resonate with classic animal work. Lesion studies in non-human primates reported that damage to premotor and posterior parietal cortices produced persistent cooling of the contralateral limb even without direct autonomic injury, hinting that cortical regions classically associated with sensorimotor integration also help regulate peripheral vasomotor responses. The new human data extend this idea by showing that activity in frontoparietal regions covaries with temperature changes during an ownership manipulation in real time. From a predictive-processing perspective, ownership illusions may engage sensory reweighting in which visual information is prioritized over competing somatosensory signals, and thermosensory input, like touch, may be downweighted during multisensory conflict, with the present oscillatory and connectivity patterns providing complementary windows onto that process.

The study has limitations the authors acknowledge: the sample comprised only healthy young adults, EEG source localization cannot definitively pinpoint anatomical generators, temperature was sampled before and after each condition rather than continuously, and the correlational design precludes causal claims about whether thermosensory signals drive ownership updates. Even so, the practical implications are tantalizing. Warming a limb has been shown to strengthen body ownership in healthy people and to correlate with recovery of ownership disturbances in a patient with somatoparaphrenia, and thermal feedback is now being built into advanced prosthetic limbs that restore natural temperature sensation to amputees. Understanding the rhythmic dialogue between frontoparietal circuits, the insula, and the skin could therefore open new rehabilitation strategies for disorders of bodily self-awareness, from stroke to eating disorders, and may even guide the design of prostheses that feel genuinely like part of the body. For now, the message is vividly simple: the warmth of your hands and the feeling that they are yours are entangled in the same slow brainwaves.

Subject of Research: The neural oscillatory mechanisms by which thermosensory signals are integrated into body ownership

Article Title: Oscillatory dynamics within fronto-insular-parietal networks integrate thermosensory signals into body ownership

Article References: Mattavelli, G., Crottini, F., Gorrino, I., Arrigoni, E., Maiocchi, C., Pisoni, A., Bottini, G., & Salvato, G. (2026). Oscillatory dynamics within fronto-insular-parietal networks integrate thermosensory signals into body ownership. iScience, 29(10), Article 117679. https://doi.org/10.1016/j.isci.2026.117679

Image Credits: AI Generated

DOI: 10.1016/j.isci.2026.117679

Keywords: body ownership, thermosensory signals, skin temperature, EEG, theta oscillations, mirror box illusion, insula, frontoparietal network, functional connectivity, bodily self-awareness, thermal imaging, neuroscience

The research, led by Matthew Leedom and Arun Singh of the University of South Dakota together with colleagues at Oregon Health & Science University and other institutions, analyzed resting-state electroencephalography recordings from 237 participants across three study sites. The cohort included 88 healthy controls and 149 people with Parkinson’s disease, all assessed in their clinically defined ON-medication state while taking their usual dopaminergic medication. Among the patients, 73 experienced freezing of gait and 76 did not, allowing the team to ask a deceptively simple question: do the brains of people with Parkinson’s, and specifically those with freezing, generate neural rhythms differently?

To answer it, the researchers abandoned the traditional approach of measuring average spectral power. Conventional EEG analysis averages oscillatory activity over time, which can obscure the fact that brain rhythms do not behave like continuous signals. Beta activity, the frequency range most closely tied to Parkinson’s motor symptoms, actually arrives in short, intermittent packets known as bursts. By detecting these bursts directly, the team could quantify how often they occurred, how long they lasted, how strong they were, and how much of the recording time the brain spent in a burst state, metrics that capture the temporal architecture of neural synchrony rather than its blunt average.

The technical execution was carefully harmonized. Because the three sites used different EEG systems with different sampling rates, the analysis was restricted to a common set of 11 electrodes spanning frontal, central, parietal, and occipital regions. The primary focus fell on the midline fronto-central Cz electrode, a location relevant to lower limb control and gait. Signals were filtered into four frequency bands, theta from 4 to 8 hertz, alpha from 8 to 13 hertz, low beta from 13 to 20 hertz, and high beta from 20 to 30 hertz, and a burst was defined as any moment when the amplitude envelope of the filtered signal exceeded the 75th percentile threshold for that participant, channel, and band. Rigorous artifact removal, independent component analysis, and false discovery rate correction for multiple comparisons guarded against spurious findings.

The headline result was strikingly frequency-specific. People with Parkinson’s disease showed significantly altered low-beta burst dynamics at the mid-frontal region: their low-beta bursts were more frequent, but shorter in duration, compared with healthy controls. Both effects survived statistical correction, with corrected p-values of 0.004 for burst rate and duration. Crucially, burst amplitude and the total proportion of time spent in a burst did not differ between groups, indicating that the disease changes the temporal organization of beta activity, its rhythm of firing and resting, rather than simply cranking up oscillatory power. Exploratory topographic maps showed that these low-beta abnormalities extended beyond the mid-frontal electrode across several central and posterior channels, consistent with the idea that beta bursts are network-level events involving distributed cortical regions rather than isolated local oscillations.

That pattern contrasts intriguingly with earlier invasive findings. Recordings from the subthalamic nucleus, a deep brain target for stimulation therapy, have typically linked prolonged beta bursts to greater motor impairment, particularly when patients are off medication. The current cortical findings, gathered at rest while patients were medicated, instead suggest a fragmentation of beta activity, more bursts that terminate quickly, possibly reflecting dopaminergic modulation, residual disease-related dysfunction, or compensatory cortical reorganization. The authors are careful to note that without simultaneous cortical-subthalamic recordings or direct ON-OFF medication comparisons, the precise mechanism remains an open question.

When the team turned to freezing of gait, the picture changed. In three-group comparisons across healthy controls, patients without freezing, and patients with freezing, low-beta burst rate and duration differed across groups, but when the analysis was restricted to Parkinson’s patients alone and adjusted for disease duration and motor severity on the MDS-UPDRS scale, no significant differences emerged between those with and without freezing. In other words, the low-beta burst abnormalities appear to mark Parkinson’s disease and general motor-network dysfunction rather than freezing specifically. Some apparent freezing-related differences in the unadjusted data likely reflected the fact that patients with freezing tend to have longer disease duration and more severe motor symptoms.

Instead, the strongest signal tied to freezing came from an entirely different frequency band. Theta burst amplitude at the mid-frontal electrode correlated positively with freezing severity, measured with site-standardized questionnaire scores. Both the median theta burst amplitude and the 90th percentile amplitude, capturing the strongest theta events, showed significant correlations with severity, with Spearman’s rho of 0.22 and corrected p-values of 0.032 and 0.028 respectively. No beta-band metric survived correction in these severity analyses. This dissociation is physiologically compelling: theta activity in mid-frontal cortex has long been linked to cognitive control and conflict monitoring, and freezing episodes are most likely to occur in situations demanding heightened executive control, such as turning, navigating doorways, or dual-tasking. Elevated theta burst amplitude could reflect greater recruitment of cognitive control networks as a compensatory response to failing automatic motor control, or alternatively a maladaptive state of network instability and excessive conflict monitoring. Because the data were cross-sectional and collected at rest, the study cannot definitively distinguish between these interpretations.

The findings carry practical implications. Burst-based EEG metrics may serve as complementary biomarkers that capture aspects of Parkinson’s pathophysiology invisible to conventional spectral analysis. A low-beta burst timing signature could help characterize motor-network dysfunction, while theta burst amplitude might offer a continuous, quantitative index of the cognitive-motor burden underlying freezing severity, potentially useful for tracking disease progression or evaluating therapies. Notably, the continuous severity measure proved more sensitive than the categorical freezing-versus-non-freezing classification, hinting that neural dysfunction accumulates along a spectrum rather than switching on at a diagnostic threshold.

The study also has honest limitations. Harmonizing to 11 channels limited spatial resolution and ruled out source localization, resting-state recordings may miss the dynamic processes that unfold during actual walking and freezing episodes, and the timing of patients’ last medication dose was not uniformly standardized across sites, leaving open whether medication itself shaped the burst patterns. FOG severity was measured with different questionnaires at different sites, requiring within-site normalization, and the operational definition of bursts via an amplitude threshold, while consistent with prior work, should not be taken to represent discrete biological events in every instance. Still, the scale of the cohort, the multi-site harmonization, and the clean frequency-specific dissociation make this one of the most systematic examinations of cortical burst dynamics in Parkinson’s disease to date. The next step, the authors suggest, is to combine standardized medication manipulations, higher-density recordings, and tasks that provoke freezing in the laboratory, bringing science closer to the moment when the brain’s rhythm of rhythm itself explains why feet freeze.

Subject of Research: Frequency-specific EEG burst dynamics in Parkinson's disease and freezing of gait

Article Title: Frequency-Specific EEG burst dynamics in Parkinson’s Disease and freezing of gait

Article References: Frequency-Specific EEG burst dynamics in Parkinson’s Disease and freezing of gait. (n.d.). https://doi.org/10.1007/s00415-026-14149-6

Image Credits: AI Generated

DOI: 10.1007/s00415-026-14149-6

Keywords: Parkinson's disease, freezing of gait, EEG, beta bursts, theta oscillations, neural oscillations, basal ganglia, motor networks, cognitive control, biomarkers, neurophysiology, Journal of Neurology