Biology subjects

Wenz, D.

Publications and source records attributed to Wenz, D..

3 recordsLinked to original sources

bioRxiv2026

A Conserved Locus Coeruleus fMRI Signature of Brain-State Transitions across Sleep, Anesthesia, and Wakefulness

Neuromodulatory systems dynamically reconfigure large-scale brain networks to support adaptation across behavioral and cognitive states. The locus coeruleus (LC), which broadcasts noradrenaline throughout the forebrain, is a central regulator of arousal and state-dependent dynamics. However, how LC activity manifests in brain-wide organization across physiological contexts, and how it biases fMRI connectivity, remains poorly understood. Using an optogenetically informed cross-species framework, we identify a transient LC-derived spatiotemporal pattern of brain activity accompanying brain-state transitions under progressively naturalistic conditions: controlled LC stimulation and endogenous LC fluctuations in anesthetized mice, sleep-wake transitions in rodents and humans, and resting-state activity in awake humans. This LC-derived signature is conserved across species and contexts, leaving a robust and detectable imprint on the BOLD signal. Critically, the prevalence of LC events systematically biases functional connectivity metrics in human fMRI. These findings establish LC activity as a mechanistically interpretable source of variability in resting-state measurements, with direct implications for the interpretation of fMRI biomarkers in arousal-related disorders.

neuroscience↗

bioRxiv2025

Ultra-High Field 31P functional Magnetic Resonance Spectroscopy Reveals NAD+ Dynamics in Brain Energy Metabolism during Visual Stimulation.

We investigated dynamic changes in nicotinamide adenine dinucleotide (NAD{square}) metabolism in the human occipital lobe using ultra-high field 31P functional magnetic resonance spectroscopy (fMRS) at 7 Tesla. Twenty-five healthy volunteers (mean age 24 {+/-} 4 years, 10 female) performed a visual task alternating between fixation and flashing checkerboard stimuli. 31P MRS spectra were acquired from a visual cortex voxel functionally localized by prior fMRI. Linear mixed-effects modelling revealed a significant reduction in NAD{square} concentrations during the first stimulation block, while no significant change was observed during the second block. No significant changes were observed for other high-energy phosphate metabolites (ATP, phosphocreatine, and inorganic phosphate), indicating specificity in the NAD{square} response. Exploratory analyses, dividing the blocks in two halves, suggested further reductions in NAD{square} and tNAD in the second halves of both stimulation blocks, though these trends were not statistically significant. Our findings demonstrate the feasibility of using fMRS at 7T to detect stimulus-induced dynamics in cerebral NAD{square} metabolism in vivo, providing insights into the interplay between glycolysis and oxidative phosphorylation during neural activation.

neuroscience↗

bioRxiv2022

Time-efficient relaxation measurements by 31P MR fingerprinting in human brain at 7T

PurposeThe goal of the study is to develop 31P spectroscopic MRF at 7T to measure T1 and T2 relaxation times simultaneously and to compare time efficiency and test-retest reproducibility of MRF with conventional inversion recovery and multi-TE methods. MethodsA 31P MRF scheme was designed based on a balanced steady-state free precession type sequence. Dictionary was generated using the Bloch equations. B0 map was acquired experimentally and incorporated into the dictionary. 7 phantoms with different T1 and T2 relaxation times were prepared for MRF validation. Simulations were performed to evaluate estimation bias. 7 volunteers were scanned twice using both MRF and the conventional methods to evaluate the reproducibility. ResultsIn phantom measurements, T1 and T2 values between MRF and conventional methods demonstrated a good agreement with Pearsons correlation coefficients of 0.99 and 0.97, respectively. In in vivo experiments, estimated T1 by MRF were in good agreement with those measured by the inversion recovery and in the literature. On the other hand, estimated T2 values by MRF were shorter than those measured by the multi-TE method. 31P MRF method can reduce the acquisition time by 15 min providing less than 10% of mean CV for T1 estimations and less than 20% of mean CV for T2 estimations of metabolites. ConclusionOur results shows the feasibility of simultaneous T1 and T2 measurement of 31P metabolites in human brain using MRF at 7T. High reproducibility can be achieved especially for T1 measurement with 40% time reduction over conventional methods.

bioengineering↗