Normal Brain Physiology by MRS & Other Modalities

Tuesday 13 May 2014

Milan Scheidegger^1,2, Alexander Fuchs¹, Simon Ametamey^3,4, Felix Kuhn⁵, Anass Johayem⁵, Alfred Buck^4,5, Erich Seifritz^2,4, and Anke Henning^1,6
1Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland, ²Department of Psychiatry, Psychotherapy, and Psychosomatics, University Hospital of Psychiatry Zurich, Zurich, Switzerland, ³Institute of Pharmaceutical Sciences, University and ETH Zurich, Zurich, Switzerland,⁴Neuroscience Center Zurich, University and ETH Zurich, Zurich, Switzerland, ⁵Division of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland, ⁶Max Planck Institute for Biological Cybernetics, Tübingen, Germany

In this multimodal, double-blind, randomized, placebo-controlled PET-MRS study in 20 healthy subjects, we report a pharmacological modulation of glutamate-dependent neuroreceptor plasticity in the pregenual anterior cingulate cortex following the administration of the NMDA-receptor antagonist ketamine. In order to investigate the functional interplay between the major excitatory neurotransmitter glutamate (Glu) and the density of the metabotropic glutamate receptor subtype 5 (mGluR5) we combined proton magnetic resonance spectroscopy (1H-MRS) with positron emission tomography (11C-ABP688-PET). Our findings complement previous reports of increased glutamate release during ketamine challenge by providing additional in vivo molecular imaging evidence for ketamine-induced neurotransmitter-receptor coupling.

Masoumeh Dehghani M.¹, Bernard Lanz¹, Nicolas Kunz², Corina Mihaela Berset², and Rolf Gruetter^1,3
1Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland, ²Center for Biomedical Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland, ³Departments of Radiology, Universities of Lausanne and Geneva, Lausanne and Geneva, Switzerland

The aim of this study is to address the diffusion characteristic of Acetate(Ace) in the rat brain in vivo using localized diffusion weighed STEAM-based spectroscopic pulse sequence. The study design is based on the assumption that intracellular and extracellular metabolites experiences different diffusion behavior. Minimizing GABA peak contribution at 1.89 ppm in 1H MR spectra improved the accuracy of the measurement of Ace time course and the Ace diffusion in brain in vivo. The significantly larger ADC of Ace compared to intracellular metabolites suggests a substantial Ace concentration in the extracellular space of rat brain during Ace infusion.

Sina Aslan^1,2, Sandra Chapman², Jeffrey Spence², Laura DeFina³, Nyaz Didehbani², and Hanzhang Lu^4
1Advance MRI, LLC, Frisco, Texas, United States, ²Center for BrainHealth, University of Texas at Dallas, Dallas, Texas, United States, ³The Cooper Institute, Dallas, Texas, United States, ⁴Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, United States

This study adds new insights into the mounting evidence of benefits from aerobic training revealing benefits across cardiovascular fitness, cognition, and regional CBF in adults. Most studies show the gains were achieved after six months of physical training. However, the present study shows gains across three domains earlier than previously documented in sedentary middle-aged to old adults. Using pCASL MRI, we measured significant CBF gains in the anterior cingulate region which has been linked to superior cognitive-agers in late life. The findings suggest that healthy life style changes in exercise habits can help to mitigate unnecessary losses.

Andrew Melbourne¹, Zach Eaton-Rosen¹, Giles Kendall², David Price³, Alan Bainbridge³, Ernest Cady³, Nicola J Robertson², Neil Marlow², and Sebastien Ourselin^1
1CMIC, University College London, London, London, United Kingdom, ²Academic Neonatology, UCL Institute for Women's Health, London, United Kingdom, ³Medical Physics, University College Hospital, London, United Kingdom

This work describes longitudinal correlations in MR spectroscopy and multi-component T2 relaxometry in a group of very-preterm infants scanned at 30 and 40 weeks equivalent gestational age.

Dace Apšvalka¹, Andrew Gadie¹, and Paul Gerald Mullins^1
1Psychology, Bangor University, Bangor, Gwynedd, United Kingdom

Improvements in scanner technologies and data acquisition and analysis methods allow magnetic resonance spectroscopy (MRS) techniques to detect neurochemical concentration changes associated with neural activity. This functional MRS (fMRS) technique is gaining increasing interest in neuroscience, however a debate exists as to whether stimulus related changes of metabolites might be reliably detected using fMRS, and if it is possible to do so at 3T. This study presents event related dynamics of glutamate (Glu) and blood-oxygen-level-dependent (BOLD) signal at 3T in a repetition suppression paradigm.

Chen Chen¹, Penny Gowland¹, Susan Francis¹, Mary Stephenson¹, Peter Morris¹, and Andrew Peters^1
1Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, Nottinghamshire, United Kingdom

31P magnetic spectroscopy with magnetisation transfer was used to investigate changes in creatine kinase (CK) kinetics induced in human visual cortex during visual stimulation by measuring the unidirectional PCr->ATP rate constant (k1). Results revealed that 1) intrinsic and apparent spin-lattice relaxation time T1 of PCr at 3T are 4.67±0.91s and 1.51±0.18s, respectively; 2) k1 increased by 17± 12 % during visual stimulation, indicating that CK turnover is elevated during increased neuronal activity.

Anouk Marsman¹, Rene C.W. Mandl¹, Dennis W.J. Klomp², Vincent O. Boer², Anna Andreychenko³, Wiepke Cahn¹, Rene S. Kahn¹, Peter R. Luijten², and Hilleke E. Hulshoff Pol^1
1Psychiatry, University Medical Center Utrecht, Utrecht, Netherlands, ²Radiology, University Medical Center Utrecht, Utrecht, Netherlands,³Radiotherapy, University Medical Center Utrecht, Utrecht, Netherlands

Minimizing energy resources may be beneficial to intelligence and a combination of higher GABA and lower glutamate (Glu) levels suggest a more efficient energy use. Performing 1H-MRS at an ultra-high field strength of 7T results in increased sensitivity and spectral resolution, which are particularly important when measuring Glu and GABA. Using 7T 1H-MRS, we found that a higher Working Memory Index (an aspect of intelligence) was associated with a significantly higher GABA/Glu ratio in the occipital cortex in healthy individuals. This suggests that individuals with a higher intelligent working memory performance make more efficient use of their brains’ energy resources.

NICOLAAS A PUTS^1,2, Ashley D Harris^1,2, Peter B Barker^1,2, and Richard A Edden^1,2
1Russell J. Morgan department of Radiology and Radiological Sciences, The Johns Hopkins University, Baltimore, Maryland, United States, ²FM Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, United States

MM-suppressed GABA concentration correlates more strongly with behavioral performance than GABA+

Michael Kelly^1,2, Hannah Hare¹, Michael Germuska¹, Nicola Filippini¹, and Daniel Bulte^1
1FMRIB Centre, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, Oxfordshire, United Kingdom, ²Centre for Core Biotechnology Services, University of Leicester, Leicester, Leicestershire, United Kingdom

Recently, respiratory-calibrated MRI methods capable of providing a quantitative assessment of cerebral physiology have been developed. In this study, respiratory-calibrated MRI was applied to healthy aged subjects to investigate the effect of potentially altered baseline physiology on the parameters quantified by respiratory-calibrated MRI. The parameters were not found to correlate with physiological parameters such as age, blood pressure, BMI and pulse rate. Oxygen extraction fraction and cerebral blood flow (CBF) were found be inversely correlated and cerebrovascular reactivity and CBF were positively correlated. These findings are in agreement with recent PET studies and provide validation of respiratory-calibrated MRI methods.

Prasanna Karunanayaka¹, Megha Vasavada¹, Michael Tobia¹, Jianli Wang¹, Paul Eslinger², and Qing X Yang^1
1Radiology, Penn State University, Hershey, Pennsylvania, United States, ²Neurology, Penn State University, Hershey, Pennsylvania, United States

Default mode Network modulations during olfactory processing can provide valuable information since both networks are implicated in higher-order cognitive processing. Network deactivation refers to a relatively higher level of neural activity during rest conditions (or low demand tasks) compared to active (or high-demand) conditions. Using olfactory fMRI, we provide direct evidence to 1) support DMN deactivation during odor stimulation and 2) establish a functional connection between olfactory and DMN networks to suggest a role for higher-order cognitive processing for olfaction.