Browsing by Subject "Neural activity"

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    Change in arteriole diameter of retina with visual simulation
    (Office of the Vice Chancellor for Research, 2016-04-08) Tellapragada, Neelima; Burns, Steven; De Castro Arribas, Alberto; Sawides, Lucie; Othman, Hind
    Neural activity and blood flow in the brain are tightly coupled. This coupling allows the brain to respond to periods of increased neural activity with increased blood flow. This coupling is known as neurovascular coupling. Many vascular based imaging techniques such as Functional MRI scans provide maps of signals of brain activity but they are limited by the resolution of fMRI to a few mm. The fMRI signal is indirect because the scanner is not tracking the neural activity directly but are measuring the changes in the blood oxygen levels. Since the retina and optic tract are part of the central nerves system and they can be measured optically it should be possible to make precise measurements of the retinal vasculature of the human retina and its response to changing stimulation levels. In this study we used an adaptive optics scanning laser ophthalmoscope (AOSLO) with multiply scattered light to measure the change in arteriolar diameter when the retina was stimulated with flickering light. We hypothesized that we could use this technique to measure both arterial dilation and time course. We used information from the reflectance of the vessel to Change in arteriole diameter of retina with visual simulation measure total vessel diameter. Images were acquired at approximately 30 Hz and averaged over 3.3 second periods. Retinal arteries were measured in five observers before, during, and after presentation of a large flickering stimulus. There was a 6-10% dilation of the blood vessels during the flicker. The Vascular dilation occurred within seconds of flickering onset and constricted again following the end of flicker stimulation. This work shows that with modern retinal imaging methods it is possible to make precise measures of vascular constriction and its time course in response to changing tissue demand.
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    Neurofluid coupling during sleep and wake states
    (Elsevier, 2023) Vijayakrishnan Nair, Vidhya; Kish, Brianna R.; Chong, Pearlynne L. H.; Yang, Ho-Ching (Shawn); Wu, Yu-Chien; Tong, Yunjie; Schwichtenberg, A. J.; Radiology and Imaging Sciences, School of Medicine
    Background: In clinical populations, the movement of cerebrospinal fluid (CSF) during sleep is a growing area of research with potential mechanistic connections in both neurodegenerative (e.g., Alzheimer's Disease) and neurodevelopmental disorders. However, we know relatively little about the processes that influence CSF movement. To inform clinical intervention targets this study assesses the coupling between (a) real-time CSF movement, (b) neuronal-driven movement, and (c) non-neuronal systemic physiology driven movement. Methods: This study included eight young, healthy volunteers, with concurrently acquired neurofluid dynamics using functional Magnetic Resonance Imaging (MRI), neural activity using Electroencephalography (EEG), and non-neuronal systemic physiology with peripheral functional Near-Infrared Spectroscopy (fNIRS). Neuronal and non-neuronal drivers were assessed temporally; wherein, EEG measured slow wave activity that preceded CSF movement was considered neuronally driven. Similarly, slow wave oscillations (assessed via fNIRS) that coupled with CSF movement were considered non-neuronal systemic physiology driven. Results and conclusions: Our results document neural contributions to CSF movement were only present during light NREM sleep but low-frequency non-neuronal oscillations were strongly coupled with CSF movement in all assessed states - awake, NREM-1, NREM-2. The clinical/research implications of these findings are two-fold. First, neuronal-driven oscillations contribute to CSF movement outside of deep sleep (NREM-3); therefore, interventions aimed at increasing CSF movement may yield meaningful increases with the promotion of NREM sleep more generally - a focus on NREM S3 may not be needed. Second, non-neuronal systemic oscillations contribute across wake and sleep stages; therefore, interventions may increase CSF movement by manipulating systemic physiology.