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8 results on '"Nkrumah, Richard O."'

2. A Prospective Study of the Impact of Severe Childhood Deprivation on Brain White Matter in Adult Adoptees:Widespread Localized Reductions in Volume But Unaffected Microstructural Organization

Author

Mackes, Nuria K., Mehta, Mitul A., Beyh, Ahmad, Nkrumah, Richard O., Golm, Dennis, Sarkar, Sagari, Fairchild, Graeme, Dell’acqua, Flavio, and Sonuga-Barke, Edmund J.S.

Subjects
early adversity, institutional deprivation, plasticity, tractography, brain imaging, white matter structure
Abstract

Early childhood neglect can impact brain development across the lifespan. Using voxel-based approaches we recently reported that severe and time-limited institutional deprivation in early childhood was linked to sub-stantial reductions in total brain volume in adulthood, >20 years later. Here, we extend this analysis to explore deprivation-related regional white matter volume and microstructural organization using diffusion-based techni-ques. A combination of tensor-based morphometry (TBM) analysis and tractography was conducted on diffu-sion-weighted imaging (DWI) data from 59 young adults who spent between 3 and 41 months in the severely depriving Romanian institutions of the 1980s before being adopted into United Kingdom families, and 20 non-deprived age-matched United Kingdom controls. Independent of total volume, institutional deprivation was associated with smaller volumes in localized regions across a range of white matter tracts including (1) long-ranging association fibers such as bilateral inferior longitudinal fasciculus (ILF), bilateral inferior fronto-occipital fasciculus (IFOF), left superior longitudinal fasciculi (SLFs), and left arcuate fasciculus; (2) tracts of the lim-bic circuitry including fornix and cingulum; and (3) projection fibers with the corticospinal tract particularly affected. Tractographic analysis found no evidence of altered microstructural organization of any tract in terms of hindrance modulated orientational anisotropy (HMOA), fractional anisotropy (FA), or mean diffu-sivity (MD). We provide further evidence for the effects of early neglect on brain development and their persistence in adulthood despite many years of environmental enrichment associated with successful adoption. Localized white matter effects appear limited to volumetric changes with microstructural organization unaffected.

Published
2022

6. A local multi-transmit coil combined with a high-density receive array for cerebellar fMRI at 7 T

Author

Priovoulos, Nikos, Roos, Thomas, Ipek, Özlem, Meliado, Ettore F, Nkrumah, Richard O, Klomp, Dennis W J, van der Zwaag, Wietske, Priovoulos, Nikos, Roos, Thomas, Ipek, Özlem, Meliado, Ettore F, Nkrumah, Richard O, Klomp, Dennis W J, and van der Zwaag, Wietske

Abstract

The human cerebellum is involved in a wide array of functions, ranging from motor control to cognitive control, and as such is of great neuroscientific interest. However, its function is underexplored in vivo, due to its small size, its dense structure and its placement at the bottom of the brain, where transmit and receive fields are suboptimal. In this study, we combined two dense coil arrays of 16 small surface receive elements each with a transmit array of three antenna elements to improve BOLD sensitivity in the human cerebellum at 7 T. Our results showed improved B1 + and SNR close to the surface as well as g-factor gains compared with a commercial coil designed for whole-head imaging. This resulted in improved signal stability and large gains in the spatial extent of the activation close to the surface (<3.5 cm), while good performance was retained deeper in the cerebellum. Modulating the phase of the transmit elements of the head coil to constructively interfere in the cerebellum improved the B1 + , resulting in a temporal SNR gain. Overall, our results show that a dedicated transmit array along with the SNR gains of surface coil arrays can improve cerebellar imaging, at the cost of a decreased field of view and increased signal inhomogeneity.

Published
2021

7. A local multi-transmit coil combined with a high-density receive array for cerebellar fMRI at 7 T

Author

Cancer, Computational Imaging, Regenerative Medicine and Stem Cells, Circulatory Health, Brain, Highfield Research Group, Priovoulos, Nikos, Roos, Thomas, Ipek, Özlem, Meliado, Ettore F, Nkrumah, Richard O, Klomp, Dennis W J, van der Zwaag, Wietske, Cancer, Computational Imaging, Regenerative Medicine and Stem Cells, Circulatory Health, Brain, Highfield Research Group, Priovoulos, Nikos, Roos, Thomas, Ipek, Özlem, Meliado, Ettore F, Nkrumah, Richard O, Klomp, Dennis W J, and van der Zwaag, Wietske

Published
2021

8. A Prospective Study of the Impact of Severe Childhood Deprivation on Brain White Matter in Adult Adoptees: Widespread Localized Reductions in Volume But Unaffected Microstructural Organization.

Author

Mackes NK, Mehta MA, Beyh A, Nkrumah RO, Golm D, Sarkar S, Fairchild G, Dell'Acqua F, and Sonuga-Barke EJS

Subjects
Humans, Child, Preschool, Young Adult, Adult, Diffusion Tensor Imaging methods, Prospective Studies, Anisotropy, Brain diagnostic imaging, White Matter diagnostic imaging
Abstract

Early childhood neglect can impact brain development across the lifespan. Using voxel-based approaches we recently reported that severe and time-limited institutional deprivation in early childhood was linked to substantial reductions in total brain volume in adulthood, >20 years later. Here, we extend this analysis to explore deprivation-related regional white matter volume and microstructural organization using diffusion-based techniques. A combination of tensor-based morphometry (TBM) analysis and tractography was conducted on diffusion-weighted imaging (DWI) data from 59 young adults who spent between 3 and 41 months in the severely depriving Romanian institutions of the 1980s before being adopted into United Kingdom families, and 20 nondeprived age-matched United Kingdom controls. Independent of total volume, institutional deprivation was associated with smaller volumes in localized regions across a range of white matter tracts including (1) long-ranging association fibers such as bilateral inferior longitudinal fasciculus (ILF), bilateral inferior fronto-occipital fasciculus (IFOF), left superior longitudinal fasciculi (SLFs), and left arcuate fasciculus; (2) tracts of the limbic circuitry including fornix and cingulum; and (3) projection fibers with the corticospinal tract particularly affected. Tractographic analysis found no evidence of altered microstructural organization of any tract in terms of hindrance modulated orientational anisotropy (HMOA), fractional anisotropy (FA), or mean diffusivity (MD). We provide further evidence for the effects of early neglect on brain development and their persistence in adulthood despite many years of environmental enrichment associated with successful adoption. Localized white matter effects appear limited to volumetric changes with microstructural organization unaffected., (Copyright © 2022 Mackes et al.)

Published
2022
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