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

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 wurde mit Hilfe eines sauerstoffreduzierten Gasgemischs (O2-Anteil 13%) erzeugt. Die Probanden mussten insgesamt 3 MRT-Sitzungen absolvieren, um verschiedene Sauerstoffzustände zu untersuchen: Normoxie (FiO2 = 0,21), Kurzzeithypoxie (7 ± 1 min Hypoxie, FiO2 = 0,13), Langzeithypoxie (8 h und 29 ± 24 min Hypoxie, FiO2 = 0,13). Jede Sitzung dauerte ca. 30 min und bestand aus je zwei fMRI-Durchgängen (1 visuelle Aufgabe, 1 motorische Aufgabe). Die zerebralen Symptome einer Höhenkrankheit wurden mittels des LLS bewertet und der Einfluss einer Höhenkrankheit auf die Gehirnaktivierungsmuster im fMRT untersucht. Resultate: Die mittlere BOLD-Signalveränderung während Normoxie betrug bei motorischer Stimulation 2,43 ± 0,80% und bei visueller Stimulation 3,49 ± 1,41%. Bei motorischer Stimulation betrug sie nach Kurzzeithypoxie 0,55 ± 0,30% und 0,82 ± 0,62% nach Langzeithypoxie. Bei visueller Stimulation betrug die mittlere Signaländerung aufgrund von Kurzzeithypoxie 1,79 ± 0,69 und aufgrund Langzeithypoxie 2,02 ± 1,18%. ANOVA-Messungen mit den Faktoren Aufgabe (motorisch, visuell) und hypoxische Bedingungen (Kurzzeithypoxie, Langzeithypoxie) zeigten einen Effekt der Aufgabe (F (1, 15) = 52.10, p <0.001), aber keinen Effekt der hypoxischen Bedingung (F (1, 15) = 1,79, p = ns) auf die BOLD Signalwertänderungen. Schlussfolgerungen: Hypoxie führte zu einer verminderten Hirnaktivität im fMRT bei motorischer und visueller Stimulation trotz erhaltener Hirnfunktion. Die mit der Gehirnaktivierung verbundenen Veränderungen der Oxygenierung scheinen eher Einfluss auf den motorischen Bereich als den visuellen Kortex zu haben. Die Adaptationsfähigkeit an chronische hypoxische Zustände scheint sich demzufolge zwischen dem motorischen und dem visuellen System zu unterscheiden

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

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 wurde mit Hilfe eines sauerstoffreduzierten Gasgemischs (O2-Anteil 13%) erzeugt. Die Probanden mussten insgesamt 3 MRT-Sitzungen absolvieren, um verschiedene Sauerstoffzustände zu untersuchen: Normoxie (FiO2 = 0,21), Kurzzeithypoxie (7 ± 1 min Hypoxie, FiO2 = 0,13), Langzeithypoxie (8 h und 29 ± 24 min Hypoxie, FiO2 = 0,13). Jede Sitzung dauerte ca. 30 min und bestand aus je zwei fMRI-Durchgängen (1 visuelle Aufgabe, 1 motorische Aufgabe). Die zerebralen Symptome einer Höhenkrankheit wurden mittels des LLS bewertet und der Einfluss einer Höhenkrankheit auf die Gehirnaktivierungsmuster im fMRT untersucht. Resultate: Die mittlere BOLD-Signalveränderung während Normoxie betrug bei motorischer Stimulation 2,43 ± 0,80% und bei visueller Stimulation 3,49 ± 1,41%. Bei motorischer Stimulation betrug sie nach Kurzzeithypoxie 0,55 ± 0,30% und 0,82 ± 0,62% nach Langzeithypoxie. Bei visueller Stimulation betrug die mittlere Signaländerung aufgrund von Kurzzeithypoxie 1,79 ± 0,69 und aufgrund Langzeithypoxie 2,02 ± 1,18%. ANOVA-Messungen mit den Faktoren Aufgabe (motorisch, visuell) und hypoxische Bedingungen (Kurzzeithypoxie, Langzeithypoxie) zeigten einen Effekt der Aufgabe (F (1, 15) = 52.10, p <0.001), aber keinen Effekt der hypoxischen Bedingung (F (1, 15) = 1,79, p = ns) auf die BOLD Signalwertänderungen. Schlussfolgerungen: Hypoxie führte zu einer verminderten Hirnaktivität im fMRT bei motorischer und visueller Stimulation trotz erhaltener Hirnfunktion. Die mit der Gehirnaktivierung verbundenen Veränderungen der Oxygenierung scheinen eher Einfluss auf den motorischen Bereich als den visuellen Kortex zu haben. Die Adaptationsfähigkeit an chronische hypoxische Zustände scheint sich demzufolge zwischen dem motorischen und dem visuellen System zu unterscheiden

Physics Opportunities at mu+mu- Higgs Factories

We update theoretical studies of the physics opportunities presented by mu+mu- Higgs factories. Interesting measurements of the Standard Model Higgs decays into {\bar b}b, tau+tau- and WW* may be possible if the Higgs mass is less than about 160 GeV, as preferred by the precision electroweak data, the mass range being extended by varying appropriately the beam energy resolution. A suitable value of the beam energy resolution would also enable the uncertainty in the b-quark mass to be minimized, facilitating measurements of parameters in the MSSM at such a first mu+mu- Higgs factory. These measurements would be sensitive to radiative corrections to the Higgs-fermion-antifermion decay vertices, which may violate CP. Radiative corrections in the MSSM may also induce CP violation in Higgs-mass mixing, which can be probed via various asymmetries measurable using polarized mu+mu- beams. In addition, Higgs-chargino couplings may be probed at a second mu+mu- Higgs factory.Comment: Report of the Higgs factory working group of the ECFA-CERN study on Neutrino Factory & Muon Storage Rings at CERN. 28 p

Sfermion Precision Measurements at a Linear Collider

At future e+- e- linear colliders, the event rates and clean signals of scalar fermion production - in particular for the scalar leptons - allow very precise measurements of their masses and couplings and the determination of their quantum numbers. Various methods are proposed for extracting these parameters from the data at the sfermion thresholds and in the continuum. At the same time, NLO radiative corrections and non-zero width effects have been calculated in order to match the experimental accuracy. The substantial mixing expected for the third generation sfermions opens up additional opportunities. Techniques are presented for determining potential CP-violating phases and for extracting tan(beta) from the stau sector, in particular at high values. The consequences of possible large mass differences in the stop and sbottom system are explored in dedicated analyses.Comment: Expanded version of contributions to the proceedings of ICHEP'02 (Amsterdam) and LCWS 2002 (Jeju Island

Selectron production at an e-e- linear collider with transversely polarized beams

We study selectron production at an e-e- linear collider. With the help of transverse beam polarizations, we define CP sensitive observables in the production process e- e- --> selectron_L selectron_R. This process proceeds via t-channel and u-channel exchange of neutralinos, and is sensitive to CP violation in the neutralino sector. We present numerical results and estimate the significances to which the CP sensitive observables can be measured.Comment: 14 page

SPheno, a program for calculating supersymmetric spectra, SUSY particle decays and SUSY particle production at e+ e- colliders

SPheno is a program that accurately calculates the supersymmetric particle spectrum within a high scale theory, such as minimal supergravity, gauge mediated supersymmetry breaking, anomaly mediated supersymmetry breaking, or string effective field theories. An interface exists for an easy implementation of other models. The program solves the renormalization group equations numerically to two--loop order with user-specified boundary conditions. The complete one--loop formulas for the masses are used which are supplemented by two--loop contributions in case of the neutral Higgs bosons and the mu parameter. The obtained masses and mixing matrices are used to calculate decay widths and branching ratios of supersymmetric particles as well as of Higgs bosons, b -> s gamma, Delta(rho) and (g-2)_muon. Moreover, the production cross sections of all supersymmetric particle as well as Higgs bosons at e+ e- colliders can be calculated including initial state radiation and longitudinal polarization of the incoming electrons/positrons. The program is structured such that it can easily be extend to include non-minimal models and/or complex parameters.Comment: 55 pages, latex, 1 figure, v2: eq.(86) corrected, extended discussion on the implementation of b->s gamma, version to be published in Comput. Phys. Commun.; v3: typos in Eqs. 34, 38-41 corrected; v4: SUSY Les Houches accord implemented, extended discussion of low energy inpu