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Title: Investigation of vasomotion oscillations in spontaneous cortical haemodynamics
Author: Patel, Priya
ISNI:       0000 0004 6062 5141
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2016
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Vasomotion, defined as the slow rhythmic oscillations observed in spontaneous cortical haemodynamic is a signal that not completely understood. The presence of vasomotion in the haemodynamics observed in this study prompts questions as to the possible function of these oscillations. Studies conducted using urethane typically report the presence of vasomotion oscillations following urethane anaesthesia induction present in the spontaneous haemodynamics (Mayhew et al., 1996). As urethane anaesthesia is known to lower blood pressure (Maggi and Meli., 1986), this was used as a construct to measure the magnitude of vasomotion oscillations during periods of lowered and normal blood pressure. The imaging technique 2D-OIS provided measurements of changes in the haemodynamics from the whisker 'barrel' somatosensory cortex of anaesthetised rats and concurrent electrophysiological recordings of neural activity measurements was also recorded. In chapter 3, the magnitude of the vasomotion oscillations was assessed during periods of lowered and normal systemic blood pressure. Indeed, it was found that larger magnitudes of vasomotion were observed during periods of lowered blood pressure, indicating a possible concomitant relationship between the two. Chapter 4 extended the findings from chapter 3 and also observed blood oxygen saturation levels and changes in neural activity (known as cortical state). An interesting temporal relation between the two was observed whereby during periods of lowered blood pressure; the neural activity was seen to change from a state of quiescence to arousal in addition to this temporal increases in the blood oxygen saturation levels were also observed. Chapter 5 replicated the experimental paradigms of chapters 3 & 4 with the addition of an oxygen probe which was able to measure oxygenation levels in the tissue (from the same cortical region). The tissue oxygenation measurements provided additional information about the relation between cerebral tissue oxygen levels and magnitudes of vasomotion oscillations, in particular during periods of hyperoxia, as tissue oxygenation levels increases, the magnitudes of vasomotion oscillations were seen to decrease; indication of a concomitant relationship. This study showed how the magnitudes of vasomotion oscillations can be altered following changes in systemic blood pressure and tissue oxygenation levels; indication of a linked relationship. This thesis found during lower levels of systemic blood pressure, larger magnitudes of vasomotion oscillations were observed, suggestive that vasomotion could be acting as a protective mechanism under conditions of low perfusion, acting to increase oxygen delivery to tissue when blood pressure is reduced. An interesting temporal observation was found between changes in neural state and increases in blood oxygen saturation levels. This study has provided a novel investigation in investigating vasomotion and also why it is important to understand for resting state research investigating functional networks in both healthy and pathological condition such as Alzheimer's disease (AD) to consider vasomotion in the data.
Supervisor: Jones, Myles ; Berwick, Jason ; Boorman, Luke Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available