Biology subjects

Kerskens, C.

Publications and source records attributed to Kerskens, C..

8 recordsLinked to original sources

bioRxiv2026

Why the Sleeping Brain Clears

The mechanical origin of cerebrospinal fluid (CSF) and interstitial fluid (ISF) transport remains unresolved. High-frequency arterial pulsations ([~] 1 Hz) have long been proposed as a driver of CSF flow, yet multiple biomechanical analyses suggest that their ability to support deep bulk interstitial transport is severely limited by the poroelastic resistance of neural tissue. At the same time, slow-wave sleep is associated with large, synchronous CSF oscillations and enhanced clearance-related dynamics near [~] 0.05 Hz. What selects this low-frequency regime remains unclear. Here we propose a theoretical framework in which this frequency selection is not incidental, but mechanically necessary. When neural populations update their state, local thermodynamic demand induces microvascular dilation. Under intracranial volume constraints, this blood-volume expansion must, to leading order, be compensated by displacement of other intracranial volume components, including CSF. We model the poroelastic response of the interstitial matrix and obtain an effective low-pass filter for this displacement, with a nominal cut-off frequency in the slow-wave range (rc {approx} 0.05 Hz). This mechanical filter implies two distinct forcing regimes. During wakefulness, rapid commitment and sensorimotor resetting are hypothesized to generate spectrally sharp, high-frequency transients in vascular volume. Because this spectral content lies largely above the poroelastic passband, waking dynamics are predicted to be inefficient at driving deep bulk transport. Slow-wave sleep, by contrast, reduces rapid commitment-like transitions and permits smoother, more globally synchronized vascular-volume oscillations that fall within the passband and support larger-scale CSF motion. The framework yields several falsifiable predictions, including load-dependent modulation of sleep-associated CSF pulsation amplitudes, a BOLD-first / CSF-second temporal ordering during slow-wave events, and a mechanical discrepancy between deep interstitial transport and the rapid dispersion of superficial exogenous tracers. More generally, the theory advances a strong claim: the sleeping brain is mechanically privileged for large-scale CSF dynamics not because sleep introduces a new driver, but because sleep permits forcing in a frequency range that brain tissue can actually transmit.

neuroscience↗

bioRxiv2025

Quantum Holographic Dynamics in the Brain's Proton Spin Ensemble

Non-compact symmetries such as SU(1,1) govern amplification and squeezing, yet have not been directly identified in macroscopic spin ensembles. Here we apply a symmetry-based analytical framework to previously published magnetic-resonance data acquired from proton spin ensembles in the living human brain. By reanalyzing the detected signal within this framework, we identify a non-compact SU(1,1) pair sector of the full SU(4) spin algebra whose generators carry double-quantum coherence order, and exclude compact SU(2) exchange pathways as an explanation of the observed dynamics. Although the SU(1,1) pair coherence resides in the double-quantum sector, the 45{degrees}-gradient-45{degrees} readout block converts it into a detectable signal through a specific coherence-transfer pathway. We argue that the primary significance of the detected signal is as a witness of entry into a deep metric regime in which purely singlemode compression is no longer sufficient and cross-mode squeezing-like structure becomes necessary. In this sense, the signal functions first as a metric-regime witness and, more specifically, as a witness of non-compact pair-sector multiple-quantum coherence and squeezing. We then show that any strictly bipartite evaluation is obstructed in the high-temperature bulk-NMR setting, and that the appropriate entanglement framework is instead a macroscopic multiple-quantum-coherence witness. The observed signal features are consistent with metric-driven SU(1,1) pair dynamics, while definitive certification of many-body entanglement remains conditional on pathway-corrected calibration of the transfer coefficient and on evaluation of the corresponding separable MQC bound.

neuroscience↗

bioRxiv2025

Exploring Holography in Neuro-Vascular Dynamics

The holonomic brain theory--originally formulated to account for the need of non-local memory encoding in cognitive systems--could gain new theoretical traction when integrated with holographic principles from physics, most notably the AdS/CFT correspondence. Recent findings in neuroscience suggest that conformal field theories (CFTs), emerging at critical points across spatiotem-poral scales in neural dynamics, are essential for brain function. Concurrently, black-brane geometries, long studied in gravitational physics, can find unexpected analogues in the interplay of active matter dynamics and the brains neuroanatomical organization. Motivated by these parallels, we posit a generalized holographic framework and interrogate its validity through the fluid/gravity duality--a correspondence linking hydrodynamic equations to gravitational spacetime metrics. In this work, we explore the holographic principles at the Navier-Stokes regime, demonstrating that holography can model key neurophysiological mechanisms: cerebral autoregulation (the brains hemodynamic self-stabilization) and neurovascular coupling (the dynamic neuron-bloodflow interplay). This work bridges holography, active matter physics, and neuroscience, proposing a unified framework to decode the brains multiscale organization, its resilience to perturbations, and its computational capabilities. By grounding neurovascular physiology in gravitational duals, we open pathways to reinterpret brain function through the lens of emergent spacetime geometry.

biophysics↗

bioRxiv2022

Microstructural and mechanical insight into atherosclerotic plaques - an ex vivo DTI study to better assess plaque vulnerability

Non-invasive microstructural characterisation has the potential to determine the stability, or lack thereof, of atherosclerotic plaques and ultimately aid in better assessing plaques risk to rupture. If linked with mechanical characterisation using a clinically relevant imaging technique, mechanically sensitive rupture risk indicators could be possible. This study aims to provide this link - between a clinically relevant imaging technique and mechanical characterisation within human atherosclerotic plaques. Ex vivo diffusion tensor imaging, mechanical testing, and histological analysis were carried out on human carotid atherosclerotic plaques. DTI-derived tractography was found to yield significant mechanical insight into the mechanical properties of more stable and more vulnerable microstructures. Coupled with insights from digital image correlation and histology, specific failure characteristics of different microstructural arrangements furthered this finding. More circumferentially uniform microstructures failed at higher stresses and strains when compared to samples which had multiple microstructures, like those seen in a plaque cap. The novel findings in this study motivate diagnostic measures which use non-invasive characterisation of the underlying microstructure of plaques to determine their vulnerability to rupture. Statements and DeclarationsThe authors have no competing interests or declarations to declare. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=133 SRC="FIGDIR/small/508689v1_ufig1.gif" ALT="Figure 1"> View larger version (61K): org.highwire.dtl.DTLVardef@15174d8org.highwire.dtl.DTLVardef@ce3db1org.highwire.dtl.DTLVardef@344257org.highwire.dtl.DTLVardef@ef8f19_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioengineering↗

bioRxiv2022

Exploring DTI-derived metrics to non-invasively track recellularisation in vascular tissue engineering

Despite significant growth in the field of tissue engineering over the past decades, non-invasive, non-destructive methods to characterise recellularisation of grafts are lacking. Here, we investigate a non-invasive magnetic resonance imaging technique, diffusion tensor imaging (DTI), within acellular and recellularised vascular grafts. Using two decellularised porcine carotid grafts, smooth muscle cells were cultured dynamically for two weeks with terminal time points at day 3, 7, and 14. Grafts were fixed at each time point and investigated by DTI in an ex vivo set up. Semi-quantitative histology was carried out to investigate collagen, elastin, and cell density changes over time. DTI-derived metrics, namely the fractional anisotropy, mean diffusivity and tractography, not only were significantly different between day 3 and day 7 grafts, but also distinguished between acellular and recellularised grafts. Specifically, within the wet decellularised grafts, increasing fractional anisotropy was strongly correlated to increasing cell density. The results from this study show, for the first time, DTIs place in the field of tissue engineering, offering non-invasive, non-destructive insight into graft recellularisation.

bioengineering↗

bioRxiv2020

Cardiac related Complexity Changes of Zero-Quantum Coherence (ZQC) signals in Brain MR Imaging: Comparison between Young and Older Healthy Volunteers

Getting older affects both the structure of the brain and some cognitive capabilities. Until now, magnetic resonance imaging (MRI) approaches have been unable to give a coherent reflection of the cognitive declines. It shows the limitation of the contrast mechanisms used in most MRI investigations, which are indirect measures of brain activities depending on multiple physiological and cognitive variables. However, MRI signals may contain information of brain activity beyond these commonly used signals caused by the neurovascular response. Here, we apply a zero-spin echo (ZSE) weighted MRI sequence, which can detect heartbeat evoked signals (HES). Remarkably, these MRI signals have properties only known from electrophysiology. We investigated the complexity of the HES arising from this sequence in two age groups; young (18-29 years) and old (over 65 years). While comparing young and old participants, we show that the complexity of the HES decreases with age, where the stability and chaoticity of these HES are particularly sensitive to age. However, we also found individual differences which were independent of age. Complexity measures were related to scores from different cognitive batteries and showed that higher complexity may be related to better cognitive performance. These findings underpin the affinity of the HES to electrophysiological signals. The profound sensitivity of these changes in complexity shows the potential of HES for understanding brain dynamics that need to be tested in more extensive and diverse populations with clinical relevance for all neurovascular diseases.

neuroscience↗

bioRxiv2020

Diffusion tensor imaging and arterial tissue: establishing the influence of arterial tissue microstructure on fractional anisotropy, mean diffusivity and tractography

In this study we investigated the potential of diffusion tensor imaging (DTI) for providing insight into microstructural changes in arterial tissue by exploring the influence that cell, collagen and elastin content have on fractional anisotropy (FA), mean diffusivity (MD) and tractography. Five ex vivo porcine carotid artery models (n = 6 vessels each) - native, fixed native, collagen degraded, elastin degraded and decellularised - were developed to selectively remove components of arterial microstructure. Intact vessels were imaged at 7 T using a DTI protocol with b = 0 and 800 s/mm2 and 10 isotopically distributed directions. FA and MD values were evaluated in the medial layer of vessels and compared across tissue models. FA values measured in native and fixed native vessels were significantly higher (p<0.0001) than those in the elastin degraded and decellularised arteries. Collagen degraded vessels had a significantly higher (p<0.01) FA than elastin degraded and decellularised vessels. Native and fixed vessels had significantly lower (p<0.0001) MD values than elastin degraded, while the MD in decellularised arteries was significantly higher than that in both native (p<0.01) and fixed (p<0.005) tissue. Significantly lower (p<0.005) MD was measured in collagen degraded compared with the elastin degraded model. Tractography results yielded similar helically arranged tracts for native and collagen degraded vessels, whilst elastin degraded and decellularised vessels showed no consistent tracts. FA, MD and tractography were found to be highly sensitive to changes in the microstructural composition of arterial tissue, with cell content being a dominant source of the measured anisotropy in the vessel wall.

bioengineering↗

bioRxiv2017

Multiple spin echos in cerebral dynamics: Evidence for spontaneous symmetry breaking during pulsation

Recent proposals in quantum gravity have suggested that unknown systems can mediate entanglement between two known quantum systems, if and only if the mediator itself is non-classical. This approach may be applicable to the brain, where speculations about quantum operations in consciousness and cognition have a long history. Proton spins of bulk water, which most likely interfere with any brain function, can act as the known quantum systems. If an unknown mediator exists, then NMR methods based on multiple quantum coherence (MQC) can act as entanglement witness. However, there are doubts that todays NMR signals can contain quantum correlations in general, and specifically in the brain environment. Here, we used a witness protocol based on zero quantum coherence (ZQC) whereby we minimised the classical signals to circumvent the NMR detection limits for quantum correlation. For short repetitive periods, we found evoked signals in most parts of the brain, whereby the temporal appearance resembled heartbeat-evoked potentials (HEPs). We found that those signals had no correlates with any classical NMR contrast. Similar to HEPs, the evoked signal depended on conscious awareness. Consciousness-related or electrophysiological signals are unknown in NMR. Remarkably, these signals only appeared if the local properties of the magnetisation were reduced. Our findings suggest that we may have witnessed entanglement mediated by consciousness-related brain functions. Those brain functions must then operate non-classically, which would mean that consciousness is non-classical.

physiology↗