1. Neurovascular phase coherence is altered in Alzheimer’s diseaseJuliane Bjerkan, Bernard Meglič, Gemma Lancaster, Jan Kobal, Peter V. E. McClintock, Trevor J. Crawford, Aneta Stefanovska, 2025, izvirni znanstveni članek Povzetek: Alzheimer’s disease is the commonest form of dementia, but its cause still remains elusive. It is characterized by neurodegeneration, with amyloid-beta and tau aggregation. Recently, however, the roles of the vasculature and the neurovascular unit are being highlighted as important for disease progression. In particular, there is reduced microvascular density, and altered gene expression in vascular and glial cells. Structural changes naturally impact the functioning of the neurovascular unit, and the goal of the study was to quantify the corresponding changes in vivo, non-invasively. Our assessment is based on recordings of brain oxygenation, neuronal and cardiorespiratory activities, captured by functional near-infrared spectroscopy, electroencephalogram, electrocardiogram and respiration effort, respectively. Two groups were compared: an Alzheimer’s disease group (N = 19) and a control group (N = 20) of similar age. The time-series were analysed using methods that can capture multi-scale and time-varying oscillations such as the wavelet transform power and wavelet phase coherence. The Alzheimer’s disease group shows a significant decrease in the power of brain oxygenation oscillations compared to the control group. There is also a significant global reduction in the phase coherence between brain oxygenation time-series. The neurovascular phase coherence around 0.1 Hz is also significantly reduced in the Alzheimer’s disease group. In addition, the average respiration rate is increased in the Alzheimer’s disease group compared to the control group. We show that the phase coherence between vascular and neuronal activities is reduced in Alzheimer’s disease compared to the control group, indicating altered functioning of the neurovascular unit. The brain oxygenation dynamics reveals reduced power and coordination of oscillations, especially in frequency ranges that are associated with vasomotion. This could lead to reduced oxygen delivery to the brain, which could affect ATP production, and potentially reduce amyloid-beta clearance. These changes in neurovascular dynamics have potential for early diagnosis, as a marker of disease progression, and for evaluating the effect of interventions.
Ključne besede: neurovascular unit, time-frequency analysis, multi-scale oscillatory analysis, phase coherence, brain oxygenation
Objavljeno v DiRROS: 05.05.2026; Ogledov: 139; Prenosov: 92
 Celotno besedilo (6,30 MB)
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2. The phase coherence of the neurovascular unit is reduced in Huntington’s diseaseJuliane Bjerkan, Jan Kobal, Gemma Lancaster, Sanja Šešok, Bernard Meglič, Peter V. E. McClintock, Karol P. Budohoski, Peter Kirkpatrick, Aneta Stefanovska, 2024, izvirni znanstveni članek Povzetek: Huntington’s disease is a neurodegenerative disorder in which neuronal death leads to chorea and cognitive decline. Individuals with ≥40 cytosine–adenine–guanine repeats on the interesting transcript 15 gene develop Huntington’s disease due to a mutated huntingtin protein. While the associated structural and molecular changes are well characterized, the alterations in neurovascular function that lead to the symptoms are not yet fully understood. Recently, the neurovascular unit has gained attention as a key player in neurodegenerative diseases. The mutant huntingtin protein is known to be present in the major parts of the neurovascular unit in individuals with Huntington’s disease. However, a non-invasive assessment of neurovascular unit function in Huntington’s disease has not yet been performed. Here, we investigate neurovascular interactions in presymptomatic (N = 13) and symptomatic (N = 15) Huntington’s disease participants compared to healthy controls (N = 36). To assess the dynamics of oxygen transport to the brain, functional near-infrared spectroscopy, ECG and respiration effort were recorded. Simultaneously, neuronal activity was assessed using EEG. The resultant time series were analysed using methods for discerning time-resolved multiscale dynamics, such as wavelet transform power and wavelet phase coherence. Neurovascular phase coherence in the interval around 0.1 Hz is significantly reduced in both Huntington’s disease groups. The presymptomatic Huntington’s disease group has a lower power of oxygenation oscillations compared to controls. The spatial coherence of the oxygenation oscillations is lower in the symptomatic Huntington’s disease group compared to the controls. The EEG phase coherence, especially in the α band, is reduced in both Huntington’s disease groups and, to a significantly greater extent, in the symptomatic group. Our results show a reduced efficiency of the neurovascular unit in Huntington’s disease both in the presymptomatic and symptomatic stages of the disease. The vasculature is already significantly impaired in the presymptomatic stage of the disease, resulting in reduced cerebral blood flow control. The results indicate vascular remodelling, which is most likely a compensatory mechanism. In contrast, the declines in α and γ coherence indicate a gradual deterioration of neuronal activity. The results raise the question of whether functional changes in the vasculature precede the functional changes in neuronal activity, which requires further investigation. The observation of altered dynamics paves the way for a simple method to monitor the progression of Huntington’s disease non-invasively and evaluate the efficacy of treatments.
Ključne besede: neurovascular unit, time–frequency analysis multiscale, oscillatory analysis, phase coherence, brain oxygenation
Objavljeno v DiRROS: 05.05.2026; Ogledov: 109; Prenosov: 71
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3. Cortico-muscular phase connectivity during an isometric knee extension task in people with early Parkinson’s diseaseNina Omejc, Tomislav Stankovski, Manca Peskar, Miloš Kalc, Paolo Manganotti, Klaus Gramann, Sašo Džeroski, Uroš Marušič, 2025, izvirni znanstveni članek Povzetek: — Introduction: Parkinson’s disease (PD) is characterized by enhanced beta-band activity (13–30 Hz) in the motor control regions. Simultaneously, corticomuscular (CM) connectivity in the beta-band during isometric contractions tends to decline with age, in various diseases, and under dual-task conditions. Objective: This study aimed to characterize electroencephalograph (EEG) and electromyograph (EMG) power spectra during a motor task, assess CM phase connectivity, and explore how these measures are modulated by an additional cognitive task. Specifically, we focused on the beta-band to explore the relationship between heightened beta amplitude and reduced beta CM connectivity. Methodology: Early-stage people with PD and age-matched controls performed an isometric knee extension task, a cognitive task, and a combined dual task, while EEG (128ch) and EMG (2x32ch) were recorded. CM phase connectivity was assessed through phase coherence and a phase dynamics model. Results: The EEG power spectrum revealed no cohort differences in the beta-band. EMG also showed no differences up to 80 Hz. However, the combined EEG-EMG analysis uncovered reduced beta phase coherence in people with early PD during the motor task. CM phase coherence exhibited distinct scalp topography and frequency ranges compared to the EEG power spectrum, suggesting different mechanisms for pathological beta increase and CM connectivity. Additionally, phase dynamics modelling indicated stronger directional coupling from the cortex to the active muscle and less prominent phase coupling across people with PD. Despite high inter-individual variability, these metrics may prove useful for personalized assessments, particularly in people with heightened CM connectivity.
Ključne besede: electroencephalography, brain modeling, electromiography, coherence, motors, diseases, couplings, electrodes, oscillators, protocols
Objavljeno v DiRROS: 13.01.2025; Ogledov: 1088; Prenosov: 705
Celotno besedilo (3,42 MB)
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4. Imaging microvascular changes in nonocular oncological clinical applications by optical coherence tomography angiography : a literature reviewRok Hren, Gregor Serša, Urban Simončič, Matija Milanič, 2023, pregledni znanstveni članek Ključne besede: optical coherence tomography, angiography, endoscopy, oncology, skin carcinoma
Objavljeno v DiRROS: 26.07.2024; Ogledov: 1468; Prenosov: 708
Celotno besedilo (4,95 MB)
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5. Coherence and avoidance of sure loss for standardized functions and semicopulasErich Peter Klement, Damjana Kokol-Bukovšek, Blaž Mojškerc, Matjaž Omladič, Susanne Saminger, Nik Stopar, 2024, izvirni znanstveni članek Povzetek: We discuss avoidance of sure loss and coherence results for semicopulas and standardized functions, i.e., for grounded, $1$-increasing functions with value $1$ at $(1, 1, \ldots , 1)$. We characterize the existence of a $k$-increasing $n$-variate function $C$ fulfilling $A \le C \le B$ for standardized $n$-variate functions $A$, $B$ and discuss methods for constructing such functions. Our proofs also include procedures for extending functions on some countably infinite mesh to functions on the unit box. We provide a characterization when $A$ respectively $B$ coincides with the pointwise infimum respectively supremum of the set of all $k$-increasing $n$-variate functions $C$ fulfilling $A \le C \le B$.
Ključne besede: copulas, quasi-copulas, semicopulas, standardized function, coherence, avoidance of sure loss, k-increasing function
Objavljeno v DiRROS: 13.03.2024; Ogledov: 1286; Prenosov: 741
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