TRADITIONAL POSTER - ismrm

Poster Sessions
fMRI Modeling & Signal Characteristics
Hall B Tuesday 13:30-15:30
1113. An EEG Homologue of the Negative BOLD Response as Measured at 7 Tesla
Wietske van der Zwaag 1,2 , Marzia De Lucia 3 , Nadine Graedel 2 , Micah M. Murray 3 , Rolf Gruetter 1,2
1 Radiologie, Université de Lausanne, Lausanne, Vaud, Switzerland; 2 CIBM, EPFL, Lausanne, Vaud, Switzerland;
3 Electroencephalography Brain Mapping core, CHUV, Lausanne, Vaud, Switzerland
The basis of fMRI experiments is a tight coupling of neural activity with the BOLD response in both space and time. However, cross-modal negative BOLD
signal may also be caused by blood-steal effects. Here, we measure the negative BOLD signal using ultra-high field fMRI and the neuroelectrical activity as
measured by EEG in the same subjects. Neural deactivation is found in the EEG-based electrical neuroimaging maps in regions partially overlapping with
those where the negative BOLD signal is found, implying a possible neural basis for the negative BOLD response.
1114. Substantial Flow-Related Contribution in FMRI Signal Observed in Human Visual Cortex at 4T
Xiao Wang 1 , Wei Chen 1
1 Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN, United States
It is a common practice to apply a short repetition time (TR) for acquiring more fMRI volumes within a given total imaging time, thus gaining contrast-tonoise
ratio (CNR). However, both the task-evoked BOLD (T2/T2*) effect and flow-related component (R1) increases could contribute to the total percentage
change of fMRI signal. This study aims to quantitatively evaluate the BOLD and flow contributions in the fMRI signal detected by gradient echo EPI in the
human visual cortex during visual stimulation at 4T. The results show a substantially large flow-related contribution in the measured fMRI signal when TR
is short. The observed flow-related enhancement in fMRI signal is likely attributed by perfusion change, and it benefits fMRI mapping in two aspects:
improved CNR and specificity. The finding also suggests that the flow-related component needs to be considered in BOLD quantification (e.g., calibration
of CMRO2).
1115. Compromised Temporal Responsivity in Fusiform Areas by Aging
Makoto Miyakoshi 1 , Annabel Shen-Hsing Chen 2 , Kayako Matsuo 3 , Toshiharu Nakai
1 National Center for Geriatrics and Gerontology, Ohbu, Aichi, Japan; 2 Nangyang Technorogical University; 3 National Taiwan
Univsersity
To study the aging effect on neural mechanism of visual repetition, we performed an fMRI study. Participants saw inside and outside scenes repeatedly for
five blocks, and the first two blocks (eight repetitions for each scene) were compared with the last two blocks for Young and Elderly groups. The results
showed that the Elderly group has longer time-constant for the visual repetition effect to take place within fusiform areas and the occipital cortex. The results
supported the conclusion that the aging effect on visual repetition is represented by the compromised ‘slew rate’ i.e., temporal responsivity in the fusiform
gyri.
1116. Hemodynamic Response Function (HRF) Modulation by Inhaled CO2 Concentration Using Event-
Related FMRI
Chao-Chun Lin 1,2 , Yi-Jui Liu 3,4 , Chien-Kuo Chen 3 , Hsiao-Wei Peng 3 , Kuo-Fang Shao 4 , Wu-Chung Shen 1,5 ,
Chang Hing-Chiu 6
1 Department of Radiology, China Medical University Hospital, Taichung, Taiwan, Taiwan; 2 Graduate Institute of Biomedical
Electronics and Bioinformatics, National Taiwan University, Taipei, Taiwan, Taiwan; 3 Department of Automatic Control Engineering,
Feng Chia University, Taichung, Taiwan; 4 Master's Program in Biomedical Informatics and Biomedical Engineering, Feng Chia
University, Taichun, Taiwan; 5 School of Medicine, China Medical University, Taichung, Taiwan; 6 Applied Science Laboratory, GE
Healthcare Taiwan, Taipei, Taiwan
The purpose of this study was to evaluate the hemodynamic response function (HRF) change after inhalation of different carbon dioxide concentrations.
Using event-related method investigate the transient hemodynamic response function by short-time visual stimulus with different CO2 concentrations. Our
results show that the peak of HRF curve is decreased and delayed with increased inhaled CO2 concentrations, and the width of HRF curve is wider with
higher inhaled CO2 concentration.
1117. Increased Metabolic Activity, Not Preemptive Blood Flow Increase, Underlies Attentional Modulation
in Primary Visual Cortex
Farshad Moradi 1 , Richard Buxton 1
1 Radiology, University of California, San Diego, San Diego, CA, United States
Previous studies found that attention produces robust BOLD modulation with only modest increase in firing activity in primary visual cortex. This could be
due to a pure preemptive CBF increase with no relation to local neuronal firing. We tested the presence of such a mechanism using combined CBF/BOLD
measurements to estimate relative CMRO2. Results show that attentional enhancement of V1 activity involves an increase of both metabolic activity and
blood flow, rather than a preemptive increase in blood flow alone. The ratio of CBF to CMRO2 change appears to be higher when the stimulus is unattended
than when attended.
1118. Uncoupled Couplings: Combined FMRI and 1H-MRS for the Study of the Neurovascular and
Neurometabolic Coupling
Mauro DiNuzzo 1 , Federico Giove 1,2 , Bruno Maraviglia 1,2
1 Physics, Sapienza University of Rome, Rome, RM, Italy; 2 MARBILab, "Enrico Fermi" Center, Rome, Italy
Functional magnetic resonance imaging (fMRI) is widely used to map brain function. Nevertheless, it does measure neural activity only indirectly via
hemodynamic changes. Here we performed fMRI in combination with 1H-MRS in order to study the relationships between the vascular and metabolic