Room 355 BC

13:30 - 15:30

Moderators:

Josef Pfeuffer, Essa S. Yacoub

Xin Yu¹, Chunqi Qian¹, Der-Yow Chen¹, Stephen Dodd², and Alan P. Koretsky^1
1NIH, Bethesda, MD, United States, ²National Institutes of Health, Bethesda, MD, United States

How to extract specific neural information from fMRI signal remains challenging. Here, we demonstrate that fMRI onset laminar positions coincide with input neural projections in the cortex. Ascending thalamocortical input leads to fMRI onset at layer 4 and activation in motor cortex through somatomotor corticocortical connections shifts fMRI onset to layer 2/3 and 5. Following unilateral infraorbital denervation, ipsilateral fMRI activation in the deafferented barrel cortex to spared whisker input has an onset at layer 2/3 and 5, consistent with corticocortical callosal projections. This indicates that fMRI onset times may enable distinguishing thalamocortical (bottom-up) from corticocortical (top-down) inputs into cortex.

Federico De Martino^1,2, Michelle Moerel¹, Rainer Goebel¹, Kamil Ugurbil², Elia Formisano¹, and Essa S. Yacoub^2
1University of Maastricht, Maastricht, Netherlands, ²Center for Magnetic Resonance Research, Minneapolis, Minnesota, United States

We image the columnar organization and layer dependent modulation of human primary auditory cortex using high resolution T2 weighted functional imaging based on 3D-GRASE. We show a columnar arrangement of preferred frequency. Further we highlight layer dependent modulations of functional activation dependent on task. Our results show that the difference of responses to different frequencies increases in superficial layers when subjects are engaged in an auditory discrimination task, suggesting that superficial layers of A1 are modulated by the increase in feedback information during this task.

Alexander John Poplawsky¹ and Seong-Gi Kim^1
1Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, United States

The olfactory bulb is an excellent model to study laminar-specific activation because each layer has different neurophysiological roles in odorant encoding. Here, we measured signal changes across different layers of the olfactory bulb in response to an evoked odor stimulus using CBV and BOLD fMRI. We found that CBV had increased sensitivity and spatial-specificity compared to BOLD. In addition, CBV images had large activation foci surrounded by diffuse, global activation and laminar profiles that were similar to 2-deoxy-D-glucose autoradiographic studies. We conclude that CBV fMRI measures changes at sites specific to neural activity at all laminar depths.

Rosa M. Sanchez Panchuelo¹, Julien Besle², Olivier E. Mougin¹, Penelope A. Gowland¹, Richard W. Bowtell¹, Denis Schluppeck², and Susan T. Francis^1
1Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, United Kingdom, ²School of Psychology, University of Nottingham, Nottingham, United Kingdom

We exploit the improved BOLD CNR and high spatial resolution achievable at 7T to study the correlation of structure and function within the primary somatosensory cortex (S1). Using a travelling wave fMRI paradigm to map the within-digit representation of the index, middle, and ring fingers in S1, we identify multiple map reversals at the tip and base, corresponding to the boundaries between Brodmann areas 3a/3b/1/2. Based on high resolution structural MRI data, we inspect these functionally-parcellated Brodmann areas for differences in cortical thickness and MR measures (MTR and signal intensity in PSIR images) that are sensitive to myelination.

Patrick P. Gao^1,2, Jevin W. Zhang^1,2, Joe S. Cheng^1,2, Russell W. Chan^1,2, Leon C. Ho^1,2, Iris Y. Zhou^1,2, and Ed X. Wu^1,2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, Hong Kong SAR, China, ²Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, Hong Kong SAR, China

Rapid detection of sudden changes of external sensory stimulation is important for interaction with environment. In auditory neuroscience, the oddball paradigm has been frequently used to investigate how sounds are processed in different cortical and subcortical structures. Most human studies were focused on the cortical regions while recent electrophysiological studies in animals revealed that neurons in subcortical regions also respond to novel stimulus. In this study, we aim to reveal the role of rodent inferior colliculus in processing novel sounds non-invasively using BOLD fMRI.

Peter Herman¹, Basavaraju G. Sanganahalli¹, Douglas L. Rothman^1,2, Hal Blumenfeld^3,4, and Fahmeed Hyder^1,2
1Department of Diagnostic Radiology, Yale University, New Haven, CT, United States, ²Biomedical Engineering, Yale University, New Haven, CT, United States,³Neurology, Yale University, New Haven, CT, United States, ⁴Neurobiology, Yale University, New Haven, CT, United States

CMR_O2 changes were calculated with calibrated fMRI at 11.7T measurements of CBF, CBV, and BOLD responses across layers of the rat cortex. LFP and MUA measurements were compared to BOLD, CBV, CBF, and CMR_O2 responses. Surprisingly BOLD and CBV responses varied considerably across layers and were uncoupled with layer-specific neural measures - LFP was strong in all cortical layers, whereas MUA was weakest in the superficial layers. CBF was strongly correlated with LFP, whereas CMR_O2 was correlated with MUA. While these results lend experimental support for neurometabolic and neurovascular couplings across the cortex, CBF/LFP and CMR_O2 /MUA have different spatial distributions.

Dávid Z. Balla¹, Rosa M. Sanchez Panchuelo², Samuel J. Wharton², Gisela E. Hagberg^1,3, Klaus Scheffler^1,3, Susan T. Francis², and Richard W. Bowtell^2
1High-field MR Centre, Max Planck Institute for Biological Cybernetics, Tübingen, Germany, ²Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, United Kingdom, ³Department for Biomedical Magnetic Resonance Imaging, University of Tübingen, Tübingen, Germany

Gradient echo BOLD fMRI contrast was compared to the underlying local susceptibility changes, calculated from the same time-series using functional quantitative susceptibility mapping (fQSM). Comparing voxels coincidentally activated in both fQSM and GE-fMRI, differences were found between motor, visual and somatosensory paradigms in the respective brain areas. In most of these common voxels the signs of susceptibility and magnitude change were opposite confirming expectations. Yet, in a significant number of voxels the signs matched, suggesting strong non-local contributions. Experiments with the motor paradigm showed positive susceptibility shifts and magnitude signal changes in deep cortical layers.

Ian D. Driver¹, Susan T. Francis¹, and Penelope A. Gowland^1
1Sir Peter Mansfield Magnetic Resonance Centre, University of Nottingham, Nottingham, United Kingdom

This work assesses the origin of a shift to earlier BOLD onset times with increasing field strength, observed in response to a visual stimulus. Potential causes due to inflowing blood and different relative contributions of arteries and veins as a result of T2* changes across field strength are ruled out. Rather, a delayed venous blood oxygenation response with respect to blood flow increases, accompanied by a reduced capillary extravascular signal contribution at 1.5 T, consistent with previous Monte Carlo simulations, can be shown to cause the later onset time at 1.5 T compared to 7T.

Jevin W. Zhang^1,2, Condon Lau¹, Patrick P. Gao^1,2, Joe S. Cheng^1,2, Gehua Tong¹, Iris Y. Zhou^1,2, and Ed X. Wu^1,2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Hong Kong, Hong Kong SAR, China, ²Department of Electrical and Electronic Engineering, The University of Hong Kong, Hong Kong, Hong Kong SAR, China

Amplitude modulation (AM) is an essential feature of most natural acoustic signals and it is important in variety of sound perceptual tasks. The periodotopic map in inferior colliculus is based on the temporal analysis of periodic envelop or AM information. In this study we demonstrated the detection of spatial encoding of AM sound frequency using continuous bSSFP fMRI. Furthermore, the AM frequency encoding gradient was observed to be orthogonal to the sound spectrum frequency encoding or tonotopy gradient. Our findings can help us understand more about the auditory processing and hearing disorders.

Liyong Chen^1,2 and David Feinberg^2,3
1Advanced MRI Technologies, LLC, Sebastopol, CA, United States, ²Helen Wills Neuroscience Institute, University of California, Berkeley, CA, United States,³Advanced MRI Technologies, Sebastopol, CA, United States

Simultaneous multi-slab EVI is proposed and compare to multi-slab EVI and multiplexed EPI in 200 ms TR whole brain coverage and shows promise of a new fMRI acquisition strategy.