OPENING SESSION - ismrm

Monday AM
DfMRI and BOLD responses were also observed, such as negative BOLD signals accompanying positive DfMRI responses
supporting the assumption that the DfMRI and BOLD responses have different origins.
17:18 123. Exploring the Reproducibility and Consistency of Diffusion-Weighted Functional
Magnetic Resonance Imaging During Visual Stimulation Using Population-Based Activation
Map
Ruiwang Huang 1 , Bida Zhang 2
1 State Key Lab of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing , 100875, China;
2 Siemens Mindit Magnetic Resonance, Siemens Healthcare MR Collaboration NE Asia,
Human brain functional studies have been generally performed with BOLD-fMRI, but the spatial location and distribution of the
activation map is not accurate. Recently, it has been suggested that the diffusion-weighted functional magnetic resonance imaging
(dFMRI) may be sensitive to the true neuronal activation. However, the influence of b-value on the activation region is not fully
understood. Here we performed a visual stimulation study on twelve subjects with dFMRI (b-value=50/400/800/1200/1600s/mm2)
and BOLD-fMRI, and constructed the population-based activation maps. The locations and distributions of dFMRI and BOLD-fMRI
measurements were compared, and the consistency of dFMRI study was evaluated.
17:30 124. fMRI Using a Hyperpolarized Tracer Molecule
Ute Goerke 1 , Malgorzata Marjanska 1 , Manda Vollmers 1 , Isabelle Iltis 1 , Pierre-Gilles
Henry 1 , Kamil Ugurbil 1
1 Radiology, Center for Magnetic Resonance Research, Minneapolis, MN, United States
For the first time, fMRI utilizing a hyperpolarized tracer 13 C-labeled urea was performed. Since urea does not cross the blood-brain
barrier, it is an ideal marker for perfusion changes caused by neuronal activity. The presented results were obtained in rats with
forepaw stimulation. Despite the extremely low tracer concentration in the blood in gray matter, focal activated regions were robustly
detected in all 13 C fMRI experiments.
17:42 125. Neurovascular Coupling Relationship Between Spontaneous EEG and CBF
Responses Is Sensitive to Anesthesia Depth
Xiao Liu 1,2 , Xiao-Hong Zhu 1 , Yi Zhang 1 , Wei Chen 1,2
1 CMRR, radiology, University of Minnesota, Minneapolis, MN, United States; 2 Biomedical Engineering,
University of Minnesota, Minneapolis, MN, United States
In this study, hemodynamic response function (HRF) was estimated by “deconvolution” to describe the neurovascular coupling
between spontaneous CBF and EEG signals in the rat brain acquired simultaneously under two anesthesia depths (1.8 and 2.0%
isoflurane). We found that a small change in anesthesia depth by increasing 0.2% isoflurane could significantly alter HRF in two
aspects: lengthening latency-to-peak and broadening dispersion. This result indicates that the neurovascular coupling quantified by
HRF is sensitive to anesthesia depth and this phenomenon should have implication in quantifying the resting brain connectivity and
stimulus-evoked BOLD in the anesthetized brains and understanding their underlying neurophysiology basis.
17:54 126. Behavioural Correlate of GABA Concentration in Visual Cortex
Richard A. E. Edden 1,2 , Suresh D. Muthukumaraswamy 3 , Tom Freeman, Krish D. Singh 3
1 Russell H Morgan Department of Radiology and Radiological Sciences, The Johns Hopkins University,
Baltimore, MD, United States; 2 FM Kirby Center for Functional fMRI, Kennedy Krieger Institute, Baltimore,
MD, United States; 3 CUBRIC, School of Psychology, Cardiff University, United Kingdom
Edited MRS measurements of GABA concentration in visual cortex have recently been shown to correlate with functional metrics: the
frequency of gamma ocillations, as measured by MEG; and BOLD signal change in fMRI. This study investigates whether these
individual differences have behavioural consequences, using a psychophysical paradigm to measure orientation discrimination
thresholds. Orientation discrimination has long been associated with GABAergic neurotransmission at a cellular level; we are able to
draw a similar link at the level of individual performance differences.
18:06 127. Cortical Hemodynamics and GABAergic Inhibition. Resting GABA Levels in
Human Visual Cortex Correlate with BOLD, ASL-Measured CBF and VASO-Measured
CBV Reactivity
Manus Joseph Donahue 1,2 , Jamie Near 1,2 , Peter Jezzard 1,2
1 Clinical Neurology, Oxford University, Oxford, United Kingdom; 2 Physics Division, FMRIB Centre, Oxford,
United Kingdom
Neurovascular coupling between neuronal activity, energy metabolism and cerebral blood flow (CBF) is supported by synaptic
excitation and inhibition. We show inverse correlations between synaptic inhibition (GABA concentration) and BOLD (R=0.68) and
cerebral blood volume (CBV)-weighted VASO reactivity (R=0.75) in human visual cortex. A negative correlation between baseline
GABA and baseline CBV (R=0.75) is found; however, a positive relationship between GABA and ASL reactivity (R=0.38) and
baseline CBF (R=0.67) is found, which we attribute to blood velocity discrepancies. Results provide information on the relationship
between cortical activity, GABAergic inhibition, and multimodal fMRI contrast. First two authors are equal contributors.