<i>In Vivo</i>Diffusion Tensor Imaging and Histopathology of the Fimbria-Fornix in Temporal Lobe Epilepsy

Concha, Luis; Livy, DanielJ .; Beaulieu, Christian; Wheatley, B. Matt; Gross, Donald

doi:10.1523/jneurosci.1619-09.2010

Cited by 198 publications

(189 citation statements)

References 36 publications

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“…It should be noted that despite the controversy over the interpretation of AD and RD measures (14), diffusion-imaging measures are sensitive to many tissue properties (33), including variation in myelin (34), axon diameter and packing density (35), axon permeability (33), and fiber geometry (36). Diffusion imaging can be adapted to generate axon diameter distributions (37) or estimates of myelin microstructure (38).…”

Section: Discussionmentioning

confidence: 99%

Mechanisms of white matter changes induced by meditation

Tang

Fan³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

297

233

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Using diffusion tensor imaging, several recent studies have shown that training results in changes in white matter efficiency as measured by fractional anisotropy (FA). In our work, we found that a form of mindfulness meditation, integrative body-mind training (IBMT), improved FA in areas surrounding the anterior cingulate cortex after 4-wk training more than controls given relaxation training. Reductions in radial diffusivity (RD) have been interpreted as improved myelin but reductions in axial diffusivity (AD) involve other mechanisms, such as axonal density. We now report that after 4-wk training with IBMT, both RD and AD decrease accompanied by increased FA, indicating improved efficiency of white matter involves increased myelin as well as other axonal changes. However, 2-wk IBMT reduced AD, but not RD or FA, and improved moods. Our results demonstrate the time-course of white matter neuroplasticity in short-term meditation. This dynamic pattern of white matter change involving the anterior cingulate cortex, a part of the brain network related to self-regulation, could provide a means for intervention to improve or prevent mental disorders.attention network test | anterior corona radiata | profile of mood states D iffusion tensor imaging (DTI) is a noninvasive MRI-based technique that can delineate white matter fibers in vivo. DTI is capable of measuring white matter's structural plasticity. Studies indicate that training or learning alters brain white matter (1-5). Fractional anisotropy (FA) is an important index for measuring the integrity of white matter fibers. In general, a higher FA value has been related to improved performance, and reduced FA has been found in normal aging and in neurological or psychiatric disorders (1,(6)(7)(8).FA alterations originate from several factors, such as changes in myelination, axon density, axonal membrane integrity, axon diameter, and intravoxel coherence of fiber orientation and others changes (1, 9). To understand the mechanisms of FA change, several DTI studies have examined axial diffusivity (AD) and radial diffusivity (RD), the most important indices associated with FA (6-8). Usually, alterations in AD are associated with axon morphological changes, such as changes in axonal density or caliber (10, 11). In contrast to AD, which signifies axonal morphology, RD implicates the character of the myelin. Decrease in RD implies increased myelination, and increase represents demyelination (2,3,8). This evidence in human neuroimaging studies is consistent with animal studies examining axons and myelination histologically and comparing them directly with DTI results (12, 13).To examine RD and AD it is best to have a significant change in FA (14). Thus, in our study we investigated AD and RD alteration patterns only where integrity of white matter fibers are enhanced (identified by FA increase). Numerous studies have used AD and RD changes in the location where FA changes are found to determine whether the FA changes are a result of axonic morphology or myelin (1-3, 6, 8, 1...

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Section: Discussionmentioning

confidence: 99%

Mechanisms of white matter changes induced by meditation

Tang

Fan³

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

297

233

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“…The use of such high-resolution MRI sequences noticeably facilitates the accurate identification of white matter bundles within the hypothalamus, which are subject to structural alteration in some disorders, and which are also key landmarks used in the planning of surgical approaches and electrode placement in patients. The fornix, which is composed of arch-shaped white matter fibers connecting the hippocampus to the mammillary body (Carpenter, 1985;Mark et al, 1993), has been suggested to play an important role in memory function (Tsivilis et al, 2008;Laxton et al, 2010) and has been shown to be morphologically altered in patients with temporal epilepsy (Supprian and Hofmann, 1997;Freeman et al, 2004;Concha et al, 2010). Its detailed examination is required for the surgical planning of transcallosal or transventricular tumor resection (Winkler et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

MRI atlas of the human hypothalamus

et al. 2012

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Gaining new insights into the anatomy of the human hypothalamus is crucial for the development of new treatment strategies involving functional stereotactic neurosurgery. Here, using anatomical comparisons between histology and magnetic resonance images of the human hypothalamus in the coronal plane, we show that discrete gray and white hypothalamic structures are consistently identifiable by MRI. Macroscopic and microscopic images were used to precisely annotate the MRI sequences realized in the coronal plane in twenty healthy volunteers. MRI was performed on a 1.5T scanner, using a protocol including T1-weighted 3D fast field echo, T1-weighted inversionrecovery, turbo spin echo and T2-weighted 2D fast field echo imaging. For each gray matter structure as well as for white matter bundles, the different MRI sequences were analyzed in comparison to each other. The anterior commissure and the fornix were often identifiable, while the mammillothalamic tract was more difficult to spot. Qualitative analyses showed that MRI could also highlight finer structures such as the paraventricular nucleus, the ventromedial nucleus of the hypothalamus and the infundibular (arcuate) nucleus, brain nuclei that play key roles in the regulation of food intake and energy homeostasis. The posterior hypothalamic area, a target for deep brain stimulation in the treatment of cluster headaches, was readily identified, as was the lateral hypothalamic area, which similar to the aforementioned hypothalamic nuclei, could be a putative target for deep brain stimulation in the treatment of obesity. Finally, each of the identified structures was mapped to Montreal Neurological Institute (MNI) space. Please find enclosed the revised version of our manuscript "MRI atlas of the human hypothalamus" which we have modified according to the minor comment made by the reviewer#3.We appreciated the careful and incisive evaluation of our data made by the reviewers throughout the reviewing process. We hope that the manuscript is now in suitable form for publication in Neuroimage.  New insights into the anatomy of the human hypothalamus  Specific 1.5T MRI sequences approach histological resolution within the hypothalamus  White matter bundles within the hypothalamus can be identified using 1.5T MRI  Hypothalamic gray structures can be identified using 1.5T MRI *4. HighlightsWe have revised our manuscript to address the minor point raised by reviewer 3.In the "Data analysis" paragraph of the materials and methods section it now reads: "Structures were identified visually based on our knowledge of specific landmarks obtained from anatomical-histological cross sections and with reference to previously published atlases (Swaab et al., 1993;Koutcherov et al., 2000Koutcherov et al., , 2004Koutcherov et al., 2007;Mai et al., 2008); the landmarks used, such as the optic tract, the floor of the diencephalon, the third ventricle, and the fornix, were readily and reliably identifiable in MR scans." AbstractGaining new insights into the anatomy of the hu...

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“…for axonal packing (Concha et al, 2010). Animal studies show that neurobiological events affect the diffusion parameters differently.…”

Section: Effects Of Cognitive Demandmentioning

confidence: 99%

Reduced White Matter Integrity Is Related to Cognitive Instability

Fjell

Westlye²,

Amlien³

et al. 2011

J. Neurosci.

121

106

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Increased performance variability has been demonstrated in several groups and conditions, including aging and cognitive decline. Structural brain characteristics underlying this phenomenon have so far been elusive. However, there is reason to expect that disconnectivity in associative pathways, whether caused by immature or degraded white matter (WM) tracts, will increase performance variability by neural noise. The aim of this study was to test whether the quality of WM, measured by diffusion tensor imaging, is related to performance variability in healthy adults. Intraindividual standard deviation of the reaction time (sdRT) across trials and median reaction time (mRT) from 270 participants were obtained from a speeded continuous performance task (Eriksen flanker task) with two conditions (congruent, incongruent). Tract-based spatial statistics was used to test the relationship with diffusion characteristics [fractional anisotropy (FA), mean diffusion (MD), radial diffusion (RD), axial diffusion (AD)]. Robust relationships between sdRT and all diffusion measures were found in most WM areas, independently of mRT, age, and sex. The effects were anatomically more widespread in the congruent than the incongruent condition, covering almost 50% of the voxels for RD and MD, and Ͼ25% of the voxels for FA and AD. Partial betas were in the range 0.45-0.55, and the strength of the relationships increased significantly with age. For mRT, the effects were smaller and unstable across condition. We concluded that performance variability is a likely consequence of individual differences in WM integrity, and that it is a promising behavioral correlate of individual differences in WM microstructure.

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In VivoDiffusion Tensor Imaging and Histopathology of the Fimbria-Fornix in Temporal Lobe Epilepsy

Cited by 198 publications

References 36 publications

Mechanisms of white matter changes induced by meditation

Mechanisms of white matter changes induced by meditation

MRI atlas of the human hypothalamus

Reduced White Matter Integrity Is Related to Cognitive Instability

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