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Recent Advances in High-Resolution MR Application and Its Implications for Neurovascular Coupling Research.

Harel N, Bolan PJ, Turner R, Ugurbil K, Yacoub E - Front Neuroenergetics (2010)

Bottom Line: However, a significant lack of knowledge exists regarding the cluster of intermediate-sized vessels, mainly the intracortical, connecting these two groups of vessels and where, arguably, key blood flow regulation takes place.Here, we summarize recent cutting-edge MR applications for studying neurovascular and functional imaging, both in humans as well as in animal models.If indeed such a correlation between functional (neuronal) and structural (vascular) units exist as a fundamental intrinsic cortical feature, one could conceivably delineate functional domains in cortical areas that are not known or have not been identified.

View Article: PubMed Central - PubMed

Affiliation: Center for Magnetic Resonance Research, Department of Radiology, School of Medicine, University of Minnesota Minneapolis, MN, USA.

ABSTRACT
The current understanding of fMRI, regarding its vascular origins, is based on numerous assumptions and theoretical modeling, but little experimental validation exists to support or challenge these models. The known functional properties of cerebral vasculature are limited mainly to the large pial surface and the small capillary level vessels. However, a significant lack of knowledge exists regarding the cluster of intermediate-sized vessels, mainly the intracortical, connecting these two groups of vessels and where, arguably, key blood flow regulation takes place. In recent years, advances in MR technology and methodology have enabled the probing of the brain, both structurally and functionally, at resolutions and coverage not previously attainable. Functional MRI has been utilized to map functional units down to the levels of cortical columns and lamina. These capabilities open new possibilities for investigating neurovascular coupling and testing hypotheses regarding fundamental cerebral organization. Here, we summarize recent cutting-edge MR applications for studying neurovascular and functional imaging, both in humans as well as in animal models. In light of the described imaging capabilities, we put forward a theory in which a cortical column, an ensemble of neurons involved in a particular neuronal computation is spatially correlated with a specific vascular unit, i.e., a cluster of an emerging principle vein surrounded by a set of diving arteries. If indeed such a correlation between functional (neuronal) and structural (vascular) units exist as a fundamental intrinsic cortical feature, one could conceivably delineate functional domains in cortical areas that are not known or have not been identified.

No MeSH data available.


Functional MRI reveals cortical columns in human. An example of ocular dominance (A) and orientation (B) columns fMRI maps obtain in human at 7 T magnet. The red and blue colors in (A) indicate preferences to right or left eye stimulation, whereas the color distribution in (B) represents a given voxel's preferred stimulus orientation. (Scale bar: 1.0 mm) Figure modified from Yacoub et al. (2008).
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Figure 4: Functional MRI reveals cortical columns in human. An example of ocular dominance (A) and orientation (B) columns fMRI maps obtain in human at 7 T magnet. The red and blue colors in (A) indicate preferences to right or left eye stimulation, whereas the color distribution in (B) represents a given voxel's preferred stimulus orientation. (Scale bar: 1.0 mm) Figure modified from Yacoub et al. (2008).

Mentions: From years of invasive animal studies, orientation columns in visual cortex are perhaps the best-known example of such a functional organization in the brain. Building on the accomplishments of a long series of theoretical and experimental studies on the underlying mechanisms of fMRI contrast, combined with extensive validation studies using animal models (Fukuda et al., 2006; Harel et al., 2006), our group has recently demonstrated the feasible to map columnar structures in the human brain (Yacoub et al., 2007, 2008) (Figure 4). Studies were conducted at 7T using slab selective FOV reduction for spin-echo fMRI (Duong et al., 2003), which was found to have better spatial specificity (Harel et al., 2006). The spatial resolution was: 0.5 mm × 0.5 mm× 3 mm with minimal resolution loss due to EPI blurring along the phase encode direction. TR/TE = 6000/50 ms. To minimize motion effects, subjects used a bite bar. Subjects initially participated in ODC studies (Yacoub et al., 2007) and were brought back to map orientation specific regions using the same anatomical slice.


Recent Advances in High-Resolution MR Application and Its Implications for Neurovascular Coupling Research.

Harel N, Bolan PJ, Turner R, Ugurbil K, Yacoub E - Front Neuroenergetics (2010)

Functional MRI reveals cortical columns in human. An example of ocular dominance (A) and orientation (B) columns fMRI maps obtain in human at 7 T magnet. The red and blue colors in (A) indicate preferences to right or left eye stimulation, whereas the color distribution in (B) represents a given voxel's preferred stimulus orientation. (Scale bar: 1.0 mm) Figure modified from Yacoub et al. (2008).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2967427&req=5

Figure 4: Functional MRI reveals cortical columns in human. An example of ocular dominance (A) and orientation (B) columns fMRI maps obtain in human at 7 T magnet. The red and blue colors in (A) indicate preferences to right or left eye stimulation, whereas the color distribution in (B) represents a given voxel's preferred stimulus orientation. (Scale bar: 1.0 mm) Figure modified from Yacoub et al. (2008).
Mentions: From years of invasive animal studies, orientation columns in visual cortex are perhaps the best-known example of such a functional organization in the brain. Building on the accomplishments of a long series of theoretical and experimental studies on the underlying mechanisms of fMRI contrast, combined with extensive validation studies using animal models (Fukuda et al., 2006; Harel et al., 2006), our group has recently demonstrated the feasible to map columnar structures in the human brain (Yacoub et al., 2007, 2008) (Figure 4). Studies were conducted at 7T using slab selective FOV reduction for spin-echo fMRI (Duong et al., 2003), which was found to have better spatial specificity (Harel et al., 2006). The spatial resolution was: 0.5 mm × 0.5 mm× 3 mm with minimal resolution loss due to EPI blurring along the phase encode direction. TR/TE = 6000/50 ms. To minimize motion effects, subjects used a bite bar. Subjects initially participated in ODC studies (Yacoub et al., 2007) and were brought back to map orientation specific regions using the same anatomical slice.

Bottom Line: However, a significant lack of knowledge exists regarding the cluster of intermediate-sized vessels, mainly the intracortical, connecting these two groups of vessels and where, arguably, key blood flow regulation takes place.Here, we summarize recent cutting-edge MR applications for studying neurovascular and functional imaging, both in humans as well as in animal models.If indeed such a correlation between functional (neuronal) and structural (vascular) units exist as a fundamental intrinsic cortical feature, one could conceivably delineate functional domains in cortical areas that are not known or have not been identified.

View Article: PubMed Central - PubMed

Affiliation: Center for Magnetic Resonance Research, Department of Radiology, School of Medicine, University of Minnesota Minneapolis, MN, USA.

ABSTRACT
The current understanding of fMRI, regarding its vascular origins, is based on numerous assumptions and theoretical modeling, but little experimental validation exists to support or challenge these models. The known functional properties of cerebral vasculature are limited mainly to the large pial surface and the small capillary level vessels. However, a significant lack of knowledge exists regarding the cluster of intermediate-sized vessels, mainly the intracortical, connecting these two groups of vessels and where, arguably, key blood flow regulation takes place. In recent years, advances in MR technology and methodology have enabled the probing of the brain, both structurally and functionally, at resolutions and coverage not previously attainable. Functional MRI has been utilized to map functional units down to the levels of cortical columns and lamina. These capabilities open new possibilities for investigating neurovascular coupling and testing hypotheses regarding fundamental cerebral organization. Here, we summarize recent cutting-edge MR applications for studying neurovascular and functional imaging, both in humans as well as in animal models. In light of the described imaging capabilities, we put forward a theory in which a cortical column, an ensemble of neurons involved in a particular neuronal computation is spatially correlated with a specific vascular unit, i.e., a cluster of an emerging principle vein surrounded by a set of diving arteries. If indeed such a correlation between functional (neuronal) and structural (vascular) units exist as a fundamental intrinsic cortical feature, one could conceivably delineate functional domains in cortical areas that are not known or have not been identified.

No MeSH data available.