Elucidation of White Matter Tracts of the Human Amygdala by Detailed Comparison between High-Resolution Postmortem Magnetic Resonance Imaging and Histology

Abstract

The amygdala has attracted considerable research interest because of its potential involvement in various neuropsychiatric disorders. Recently, attempts have been made using magnetic resonance imaging (MRI) to evaluate the integrity of the axonal connections to and from the amygdala under pathological conditions. Although amygdalar pathways have been studied extensively in animal models, anatomical references for the human brain are limited to histology-based resources from a small number of slice locations, orientations and annotations. In the present study, we performed high-resolution (250 μm) MRI of postmortem human brains followed by serial histology sectioning. The histology data were used to identify amygdalar pathways, and the anatomical delineation of the assigned structures was extended into 3D using the MRI data. We were able to define the detailed anatomy of the stria terminalis and amygdalofugal pathway, as well as the anatomy of the nearby basal forebrain areas, including the substantia innominata. The present results will help us understand in detail the white matter structures associated with the amygdala, and will serve as an anatomical reference for the design of in vivo MRI studies and interpretation of their data.

Mapping the trajectory of the amygdalothalamic tract in the human brain

“…The stria terminalis and ventral amygdalofugal tracts project from the amygdala to the preoptic and tuberal nuclei of the hypothalamus and also to the septal nuclei (Kamali et al, ). The results of our two recent studies regarding the first time tractography of the amygdalofugal tract and stria terminalis were just validated by a post mortem DTI study acquired with .25 mm isotropic resolution and data averaging over 24 hr (Mori et al, ).…”

“…Despite these attempts, numerous anatomical details in the brain including the delicate pathways of the limbic system have been indiscernible or poorly detectable in prior DTT studies (Catani & Thiebaut de Schotten, ; Colnat‐Coulbois et al, ; Schmahmann, Smith, Eichler, & Filley, ). To overcome these issues, a few recent DTI tractography studies have used diffusion spectrum imaging (DSI), higher magnetic field strength on postmortem human central nervous system (Cho et al, ; Mori et al, ; Zeineh, Holdsworth, Skare, Atlas, & Bammer, ). Despite these attempts, the trajectory of the ATT has not been elucidated in prior DTT studies.…”

Dysfunctional effort-based decision-making underlies apathy in genetic cerebral small vessel disease

“…The anterior cingulum is closely associated with the overlying anterior cingulate cortex, and reduced fractional anisotropy within this tract has been linked to apathy in sporadic SVD ( Hollocks et al , 2015 ) and Alzheimer’s disease ( Kim et al , 2011 ), as well as reduced motivation in healthy people ( Bonnelle et al , 2016 ). The identified ventral white matter region associated with OFC-ACC lies medial to the uncinate fasciculus and may represent the amygdalofugal pathway, a tract that links amygdala and regions including ventral striatum and medial frontal cortex ( Miller et al , 2010 ; Mori et al , 2017 ). The anterior limb of the internal capsule contains fibres projecting between anterior and mediodorsal thalamus and prefrontal and anterior cingulate cortex and has recently been associated with apathy in frontotemporal lobar degeneration ( Lansdall et al , 2018 ).…”

XTRACT - Standardised protocols for automated tractography in the human and macaque brain

“…We should point out that due to the relatively small size of the stria terminalis and its close proximity to the fornix, the fornix tracking may leak into the stria terminalis. This is a common issue in diffusion tractography and is yet to be overcome using approaches in line with those used in the current study (Kamali et al, 2015;Mori et al, 2017;Mori and Aggarwal, 2014;Pascalau et al, 2018).…”