During the first 4 years of this grant, we have challenged the limits of BOLD fMRI to the level of sub-millimeter structures (i.e. cortical columns) in humans and laminar specificity in the animal model. In this work we established the SE BOLD technique at high fields, to be more suitable for mapping columnar structures in humans, where, in the general case, large vessels cannot be easily avoided in the imaging region of interest and can sometimes contaminate GE BOLD images. Furthermore, our strategy of employing high-field SE BOLD contrast has allowed us to explore, in addition to ODCs, orientation columns in the human brain, which were previously unmapped. Although several fMRI studies have succeeded in mapping ocular dominance columns (ODCs) in humans, since the initial ODC fMRI work in humans over 6 years ago, there has been very little advancement in this pursuit until our recent work. Furthermore, there have been no studies to date that have mapped columns using fMRI in the monkey. This prolonged silence is not only a reflection of the difficulty and limitations of lower field and/or GE BOLD techniques, but also technical issues incurred at high fields which ultimately limit high field fMRI applications to limited volumes, especially in humans. To date, there remains a lack of a general imaging strategy that works for all high resolution human studies, as depending on the neuroscience question being asked different approaches might be more suitable. In the next cycle of this grant we would like to build on our findings and extend the methods and tools for high resolution human fMRI to pave the way for further investigations of unexplored and/or unknown functional systems or architectures at the millimeter and sub-millimeter levels. These endeavors will be facilitated via larger volume high resolution fMRI acquisitions in humans as well as continued application and development of a high resolution animal fMRI model. With the proliferation of 7 Tesla magnets there is a fundamental need to establish methods and strategies for human fMRI (on these clinical scanners) which will generally be predicated on the principle that higher fields provide higher spatial resolutions and spatial specificity and thus the ability to map and/or better characterize higher resolution functional architectures, such as columns or laminar connections, or commonly studied applications such as resting state networks or visual object recognition (despite facing numerous confounds and technical limitations).
The non-invasiveness of magnetic resonance imaging (MRI) permits the study of intrinsic functional architectures in the human brain, which is not possible via other methodologies. Such investigations into the human brain have been demonstrated as relevant for diagnoses and characterizations of disease states, which can sometimes disrupt functional organizations. Magnets operating at the high magnetic field of 7 Tesla are currently being installed with clinical interfaces and the development and optimization of imaging techniques to investigate the working human brain with high spatial resolution and specificity, facilitated by high magnetic fields, will be essential for use in a clinical setting.
| Chaimow, Denis; Yacoub, Essa; Ugurbil, Kamil et al. (2011) Modeling and analysis of mechanisms underlying fMRI-based decoding of information conveyed in cortical columns. Neuroimage 56:627-42 |
| Moeller, Steen; Yacoub, Essa; Olman, Cheryl A et al. (2010) Multiband multislice GE-EPI at 7 tesla, with 16-fold acceleration using partial parallel imaging with application to high spatial and temporal whole-brain fMRI. Magn Reson Med 63:1144-53 |
| Zhang, Nanyin; Zhu, Xiao-Hong; Yacoub, Essa et al. (2010) Functional MRI mapping neuronal inhibition and excitation at columnar level in human visual cortex. Exp Brain Res 204:515-24 |
| Zhang, Nanyin; Yacoub, Essa; Zhu, Xiao-Hong et al. (2009) Linearity of blood-oxygenation-level dependent signal at microvasculature. Neuroimage 48:313-8 |
