Bok’s equi-volume principle: Translation, historical context, and a modern perspective

Consolini, Jack; Demirci, Nagehan; Fulwider, Andrew; Hutsler, Jeffrey J.; Holland, Maria A.

doi:10.1016/j.brain.2022.100057

Cited by 11 publications

(4 citation statements)

References 51 publications

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“…To construct the central GM surfaces, we used CAT12 r2560 [11][12][13][14] to segment the head-masked, co-registered R1-maps and followed the iso-volume approach 15,16 . By sampling each R1-map on their corresponding central GM surface and projecting out the local curvature 1 , we obtained curvature-corrected central GM R1-surfaces for each of the three excitation pulse amplitude scalings within each protocol.…”

Section: Methodsmentioning

confidence: 99%

A 3T investigation ofB₁⁺-inhomogeneity tolerance in MP2RAGE-basedR₁-mapping by calculating second contrast that permits previously problematic sequence parameters

Ruijters,

Lund,

Vinding

2024

Preprint

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PurposeRegarding robustR1-mapping, the goal of the present paper is twofold. First, to verify that non-bijective mapping in MP2RAGE imaging can be resolved through a 2D look-up table approach. Second, that the expanded parameter space from this can be used to improveB1+-inhomogeneity tolerance without other prerequisites.Theory and Methods: By deriving a second contrast from the magnitude images of the MP2RAGE acquisition, ambiguities in the original unified MP2RAGE image can be resolved. Such ambiguities may occur when sequences are optimised, e.g., for higherB1+-inhomogeneity tolerance. A 2D look up procedure can then be used to derive accurateR1-maps.ResultsWe acquired two sets of images, one according to a standard MP2RAGE protocol, and one optimised forB1+-inhomogeneity contrast, the latter resulting in non-bijective mapping. For each protocol, we acquired three images, using different excitation pulse amplitude scalings to magnify theB1+-inhomogeneities between images. TheR1-maps resulting from the B1+-optimised sequence showed greatly reducedB1+-effects across images, while these maps could only successfully be derived by 2D look-up approach.ConclusionWe show that it is indeed possible to improveB1+-inhomogeneity tolerance in MP2RAGE through sequence parameter settings, while still successfully estimating theR1-map with a 2D look-up table approach. The increased parameter space enabled by the 2D look-up approach may further be used to adjust MP2RAGE acquisitions for improved scan times or improved contrasts.

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Section: Methodsmentioning

confidence: 99%

A 3T investigation ofB₁⁺-inhomogeneity tolerance in MP2RAGE-basedR₁-mapping by calculating second contrast that permits previously problematic sequence parameters

Ruijters,

Lund,

Vinding

2024

Preprint

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“…The grey matter was divided into three equivolume layers using the level set method (described in detail in [66] and [67]) following the principle that the layers of the cortex maintain their volume ratio throughout the curves of the gyri and sulci [68,69]. The equivolume model transforms a desired volume fraction into a distance fraction, taking the local curvature of the pial and WM surfaces at each voxel into account [70].…”

Section: Methodsmentioning

confidence: 99%

Communication of perceptual predictions from the hippocampus to the deep layers of the parahippocampal cortex

Warrington,

Graedel,

Callaghan

et al. 2024

Preprint

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Current evidence points to the hippocampus as an essential region coordinating learning and exploiting predictive relationships in the service of perception. However, it remains unclear whether the hippocampus drives the communication of predictions to the sensory cortex or acts as a recipient of predictions from elsewhere. Here, we collected sub-millimetre 7T fMRI data to investigate neural signals in the medial temporal lobe (MTL). We used layer-specific fMRI to infer the direction of communication between the hippocampus and cortex. Specifically, superficial layers of the MTL cortex project to the hippocampus, while deep MTL layers receive feedback projections. Participants performed a task in which auditory cues predicted abstract shapes. Crucially, we omitted the expected shape on 25% of trials, thus isolating the prediction signal from bottom-up input and allowing us to ask: In which direction are predictions communicated between the hippocampus and neocortex? Neural patterns in CA23, pre/parasubiculum and the parahippocampal cortex (PHC) reflected shape-specific predictions. Layer-specific informational connectivity analyses revealed that communication between CA23 and PHC was specific to the deep layers of PHC. These findings are in line with the hippocampus generating predictions through pattern completion in CA23 and feeding these predictions back to the neocortex.

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“…It has been hypothesized that cortical layer morphology varies due to equivolumetric deformation within cortical columns [ 21 , 22 ]. In gyral columns, a constant volume ratio is maintained because outer regions are wider due to layers being thinner while inner regions are narrower due to layers being thicker.…”

Section: Methods Detailsmentioning

confidence: 99%

Multidimensional Alternating Kernel Method for cortical layer segmentation in 3D reconstructed histology

Kutten,

Trieu,

Dawson

et al. 2024

MethodsX

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Bok’s equi-volume principle: Translation, historical context, and a modern perspective

Cited by 11 publications

References 51 publications

A 3T investigation ofB₁⁺-inhomogeneity tolerance in MP2RAGE-basedR₁-mapping by calculating second contrast that permits previously problematic sequence parameters

A 3T investigation ofB₁⁺-inhomogeneity tolerance in MP2RAGE-basedR₁-mapping by calculating second contrast that permits previously problematic sequence parameters

Communication of perceptual predictions from the hippocampus to the deep layers of the parahippocampal cortex

Multidimensional Alternating Kernel Method for cortical layer segmentation in 3D reconstructed histology

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Bok’s equi-volume principle: Translation, historical context, and a modern perspective

Cited by 11 publications

References 51 publications

A 3T investigation ofB1+-inhomogeneity tolerance in MP2RAGE-basedR1-mapping by calculating second contrast that permits previously problematic sequence parameters

A 3T investigation ofB1+-inhomogeneity tolerance in MP2RAGE-basedR1-mapping by calculating second contrast that permits previously problematic sequence parameters

Communication of perceptual predictions from the hippocampus to the deep layers of the parahippocampal cortex

Multidimensional Alternating Kernel Method for cortical layer segmentation in 3D reconstructed histology

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Product

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A 3T investigation ofB₁⁺-inhomogeneity tolerance in MP2RAGE-basedR₁-mapping by calculating second contrast that permits previously problematic sequence parameters

A 3T investigation ofB₁⁺-inhomogeneity tolerance in MP2RAGE-basedR₁-mapping by calculating second contrast that permits previously problematic sequence parameters