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1. Blöchinger, Julian. Effects of normobaric hypoxia on the activation of motor and visual cortex areas in functional magnetic resonance imaging (fMRI).

Degree: PhD, Medizinische Fakultät, 2018, Ludwig-Maximilians-Universität

Aims: Hypoxia due to high altitude or otherwise altered fraction of inspired O2 affects cerebral mechanisms. Human brain function can be assessed indirectly via examination of local changes in haemodynamics in fMRI. The aim of this study was to examine if adaptation to normobaric hypoxia determines divergent activation in the brain regions supplied by the main cerebral arterial vessels. Methods: Visual and motor paradigms were used to shed light on the activation of different brain regions in fMRI under normobaric hypoxic conditions in 16 healthy male subjects. Hypoxia was produced by reducing the percentage of O2 in an inhaled gas mixture resulting in normobaric hypoxia with an FiO2 of 13 %. Participants had to complete a total of 3 MRI sessions to study different oxygen conditions: normoxia (FiO2 = 0.21, normal pressure), short-time (7 ± 1 min, FiO2 = 0.13, normal pressure), longtime hypoxia (8 h and 29 ± 24 min, FiO2 = 0.13, normal pressure). Each session lasted approximately 30 min, consisting of two fMRI runs (1 visual task, 1 motor task) which were pseudo-randomized between participants, followed by the structural sequence. Cerebral symptoms of AMS were assessed by means of the LLS and it was examined if symptomatic AMS has consequences on brain activation patterns measured as ∆S values. Results: Mean ∆S during normoxia was 2.43 ± 0.80 % due to motor stimulation, and 3.49 ± 1.41 % due to visual stimulation. During motor stimulation, the mean signal change due to short-time hypoxia was 0.55 ± 0.30 % and 0.82 ± 0,62 % due to longtime hypoxia. During visual stimulation, the mean signal change due to short-time hypoxia was 1.79 ± 0.69 %. Long-time hypoxia led to a mean signal change of 2.02 ± 1.18 %. Repeated ANOVA measures with factors task (motor, visual) and the hypoxic conditions (short-time hypoxia, long-time hypoxia) showed a main effect of task (F (1,15) = 52.10, p < 0.001), but no main effect of the hypoxic condition (F (1, 15) = 1.79, p = ns). Conclusions: Hypoxia led to diminished cerebral activation during motor and visual stimulation in spite of a preserved cerebral function. The oxygenation changes associated with brain activation seem more influential on the motor area, rather than the visual cortex. Therefore, the capability of the human brain to acclimatise to chronic hypoxic conditions may vary in the motor and the visual system.

Ziele: Hypoxie aufgrund großer Höhe oder eines anderweitig veränderten Anteils von eingeatmetem O2-Gehalts beeinflusst zerebrale Mechanismen. Die menschliche Gehirnfunktion kann indirekt über den Nachweis lokaler hämodynamischer Veränderungen im fMRT bestimmt werden. Das Ziel dieser Studie war es, zu untersuchen, ob die Anpassung an normobare Hypoxie eine unterschiedliche Aktivierung in von den drei Hauptgefäßen versorgten Gehirnregionen erzeugt. Methoden: Bei 16 gesunden, männlichen Probanden wurden visuelle und motorische Testparadigmen angewendet, um die Aktivierung verschiedener Hirnregionen im fMRT unter normobaren, hypoxischen Bedingungen aufzuklären. Hypoxie…

Advisors/Committee Members: Feddersen, Berend (advisor).

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APA (6th Edition):

Blöchinger, J. (2018). Effects of normobaric hypoxia on the activation of motor and visual cortex areas in functional magnetic resonance imaging (fMRI). (Doctoral Dissertation). Ludwig-Maximilians-Universität. Retrieved from https://edoc.ub.uni-muenchen.de/22681/

Chicago Manual of Style (16th Edition):

Blöchinger, Julian. “Effects of normobaric hypoxia on the activation of motor and visual cortex areas in functional magnetic resonance imaging (fMRI).” 2018. Doctoral Dissertation, Ludwig-Maximilians-Universität. Accessed September 23, 2018. https://edoc.ub.uni-muenchen.de/22681/.

MLA Handbook (7th Edition):

Blöchinger, Julian. “Effects of normobaric hypoxia on the activation of motor and visual cortex areas in functional magnetic resonance imaging (fMRI).” 2018. Web. 23 Sep 2018.

Vancouver:

Blöchinger J. Effects of normobaric hypoxia on the activation of motor and visual cortex areas in functional magnetic resonance imaging (fMRI). [Internet] [Doctoral dissertation]. Ludwig-Maximilians-Universität; 2018. [cited 2018 Sep 23]. Available from: https://edoc.ub.uni-muenchen.de/22681/.

Council of Science Editors:

Blöchinger J. Effects of normobaric hypoxia on the activation of motor and visual cortex areas in functional magnetic resonance imaging (fMRI). [Doctoral Dissertation]. Ludwig-Maximilians-Universität; 2018. Available from: https://edoc.ub.uni-muenchen.de/22681/

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