We examine neural correlates of discrete expressions of negative emotionality in infants to determine whether the microstructure of white matter tracts at 1 month of age foreshadows the expression of ...specific negative emotions later in infancy. Infants (n = 103) underwent neuroimaging at 1‐month, and mothers reported on infant fear, sadness, and anger at 6, 12, and 18 months using the Infant Behavior Questionnaire‐Revised. Levels and developmental change in fear, sadness, and anger were estimated from mother reports. Relations between MRI and infant emotion indicated that 1‐month white matter microstructure was differentially associated with level and change in infant fear, but not anger or sadness, in the left stria terminalis (p < 0.05, corrected), a tract that connects frontal and tempo‐parietal regions and has been implicated in emerging psychopathology in adults. More relaxed constraints on significance (p < 0.10, corrected) revealed that fear was associated with lower white matter microstructure bilaterally in the inferior portion of the stria terminalis and regions within the sagittal stratum. Results suggest the neurobehavioral uniqueness of fear as early as 1 month of age in regions that are associated with potential longer‐term outcomes. This work highlights the early neural precursors of fearfulness, adding to literature explaining the psychobiological accounts of affective development.
Highlights
Expressions of infant fear and anger, but not sadness, increase from 6 to 18 months of age.
Early neural architecture in the stria terminalis is related to higher initial levels and increasing fear in infancy.
After accounting for fear, anger and sadness do not appear to be associated with differences in early white matter microstructure.
This work identifies early neural precursors of fearfulness as early as 1‐month of age.
We examine neural correlates of discrete expressions of negative emotionality in infants to determine whether the microstructure of white matter tracts at 1 month of age foreshadows the expression of specific negative emotions later in infancy. Results indicate that 1‐month white matter microstructure was differentially associated with level and change in infant fear, but not anger or sadness, in the left stria terminalis (p < .05, corrected), a tract that connects frontal and tempo‐parietal regions and has been implicated in emerging psychopathology in adults. This work highlights the early neural precursors of fearfulness, adding to literature explaining the psychobiological accounts of affective development.
It is still a topic of research if specific clinical presentations of motoneuron disease (MND) patients should be classified as amyotrophic lateral sclerosis (ALS) variants, i.e. primary lateral ...sclerosis (PLS) with predominant upper motor neuron on the one hand and pure lower motor neuron disease (LMND) on the other hand. Objective markers for ALS are to be investigated in these patients.
The aim of the study was to investigate white matter damage by a hypothesis-guided tract-of-interest-based approach in patients with classical ALS, LMND, and PLS in contrast to healthy controls in order to challenge the hypothesis that brain structural changes according to the neuropathologically defined ALS affectation pattern (Kassubek et al., 2014) can be observed. LMND data were pooled from previous studies at two different study sites (Ulm, Germany and Milano, Italy).
DTI-based white matter integrity mapping was performed by voxelwise statistical comparison and by a tractwise analysis of fractional anisotropy (FA) maps according to the ALS-staging pattern for 65 LMND patients (clinically differentiated in fast and slow progressors), 42 PLS patients, and 101 ALS patients with a ’classical’ phenotype vs 92 matched controls to identify white matter structural alterations.
The analysis of predefined tracts-of-interest according to the neuropathological spreading pattern demonstrated regional characteristic alteration patterns (FA reductions) fast LMND progressors and in ALS compared to controls. (Müller et al., 2018) The degree of involvement correlated with the clinical phenotype. PLS also presented substantial tract involvement in the tract-of-interest-based approach.
In the tract-specific analysis according to the ALS-staging pattern, upper (PLS) as well as lower motor neuron disease (LMND) pathology showed alterations of ALS-related corticoefferent fibers. The neuroimaging results confirm the clinical approach to these phenotypes as ALS variants, in accordance with the latest revision of the El Escorial criteria for ALS, in favour of the consequence to treat these patients like ALS and also to include them into clinical trials of ALS.
Imaging-based quantitative measures from diffusion-weighted MRI (dMRI) offer the ability to non-invasively extract microscopic information from human brain tissues. Group-level comparisons of such ...measures represent an important approach to investigate abnormal brain conditions. These types of analyses are especially useful when the regions of abnormality spatially coincide across subjects. When this is not true, approaches for individualized analyses are necessary. Here we present a framework for single-subject multidimensional analysis based on the Mahalanobis distance. This is conducted along specific white matter pathways represented by tractography-derived streamline bundles. A definition for abnormality was constructed from Wilk's criterion, which accounts for normative sample size, number of features used in the Mahalanobis distance, and multiple comparisons. One example of a condition exhibiting high heterogeneity across subjects is traumatic brain injury (TBI). Using the Mahalanobis distance computed from the three eigenvalues of the diffusion tensor along the cingulum, uncinate, and parcellated corpus callosum tractograms, 8 severe TBI patients were individually compared to a normative sample of 49 healthy controls. For all TBI patients, the analyses showed statistically significant deviations from the normative data at one or multiple locations along the analyzed bundles. The detected anomalies were widespread across the analyzed tracts, consistent with the expected heterogeneity that is hallmark of TBI. Each of the controls subjects was also compared to the remaining 48 subjects in the control group in a leave-one-out fashion. Only two segments were identified as abnormal out of the entire analysis in the control group, thus the method also demonstrated good specificity.
A key set of connections necessary for the most complex brain functions are the long association cortico‐cortical fiber tracts. These pathways have been described by the Dejerines and others using ...post mortem histological or brain dissection techniques. Given methodological limitations, these fiber connections have not been delineated completely in humans. Although the stem portions of fiber tracts have been identified in humans, their precise origins and terminations remain to be determined. By contrast, the origins and terminations as well as the stems of long cortico‐cortical association fiber pathways in monkeys have been detailed in the macaque monkey brain using experimental tract tracing methods. Deepak Pandya made major contributions to the delineation of fiber tracts in the monkey brain. In the early 1990s, he compared his observations in monkeys with the original descriptions in humans by the Dejerines. With the advent of diffusion‐weighted imaging, Dr. Pandya extended this line of investigation to the human brain with Dr. Nikos Makris. In this translational analysis of long association cortico‐cortical fiber tracts, they applied a principle of extrapolation from monkey to human. In the present study, we addressed the reasoning and the complex methodology in translating brain structural connectivity from monkey to human in one cortico‐cortical fiber tract, namely the superior fronto‐occipital fascicle, which was delineated in both species by Dr. Pandya and colleagues. Furthermore, we represented this information in the form of connectional matrices in the context of the HOA2.0‐ComPaRe framework, a homological monkey‐to‐human translational system used in neuroimaging.
Direct information about origins and terminations of cortico‐cortical long association fiber pathways in humans is extremely limited. The topographic location and trajectory of cortico‐cortical association pathway stems in humans and nonhuman primates is similar (1), but only in nonhuman primates is there complete information on origins and terminations as well as stems. Thus, an extrapolation approach, from nonhuman primate to human (2), is applied in the present report to infer connectivity patterns for the superior fronto‐occipital fascicle in the human brain.
Very high gradient amplitudes played out over extended time intervals as required for second-order motion-compensated cardiac DTI may violate the assumption of a linear time-invariant gradient system ...model. The aim of this work was to characterize diffusion gradient-related system nonlinearity and propose a correction approach for echo-planar and spiral spin-echo motion-compensated cardiac DTI.
Diffusion gradient-induced eddy currents of 9 diffusion directions were characterized at b values of 150 s/mm
and 450 s/mm
for a 1.5 Tesla system and used to correct phantom, ex vivo, and in vivo motion-compensated cardiac DTI data acquired with echo-planar and spiral trajectories. Predicted trajectories were calculated using gradient impulse response function and diffusion gradient strength- and direction-dependent zeroth- and first-order eddy current responses. A reconstruction method was implemented using the predicted
-space trajectories to additionally include off-resonances and concomitant fields. Resulting images were compared to a reference reconstruction omitting diffusion gradient-induced eddy current correction.
Diffusion gradient-induced eddy currents exhibited nonlinear effects when scaling up the gradient amplitude and could not be described by a 3D basis alone. This indicates that a gradient impulse response function does not suffice to describe diffusion gradient-induced eddy currents. Zeroth- and first-order diffusion gradient-induced eddy current effects of up to -1.7 rad and -16 to +12 rad/m, respectively, were identified. Zeroth- and first-order diffusion gradient-induced eddy current correction yielded improved image quality upon image reconstruction.
The proposed approach offers correction of diffusion gradient-induced zeroth- and first-order eddy currents, reducing image distortions to promote improvements of second-order motion-compensated spin-echo cardiac DTI.
Millions of women worldwide use oral contraceptives (i.e., birth control pill; OCs), often starting during puberty/adolescence; however, it is unknown how OC use during this critical period of ...development affects the brain, especially with regard to emotional working memory. Here, we examined stress reactivity, and brain structure and function in OC users using the Trier Social Stress Test and structural and functional magnetic resonance imaging (MRI). Our results show that OC use during puberty/adolescence gives rise to a blunted stress response and alters brain activation during working memory processing. OC use, in general, is also linked to increased prefrontal brain activation during working memory processing for negatively arousing stimuli. OC use is also related to significant structural changes in brain regions implicated in memory and emotional processing. Together, these findings highlight that OC use induces changes to brain structure and function and alters stress reactivity. These findings may provide a mechanistic insight for the increased vulnerability to mood-related mental illness in women after OC use.
•OC use during puberty reduces stress reactivity.•OC use during puberty increases brain activity when working memory is engaged.•General OC use is related to structural and functional differences.•OC use alters the mediating role of progesterone on emotional stimuli sensitivity.
Purpose
Subject head motion is a major challenge in DWI, leading to image blurring, signal losses, and biases in the estimated diffusion parameters. Here, we investigate a combined application of ...prospective motion correction and spatial‐angular locally low‐rank constrained reconstruction to obtain robust, multi‐shot, high‐resolution diffusion‐weighted MRI under substantial motion.
Methods
Single‐shot EPI with retrospective motion correction can mitigate motion artifacts and resolve any mismatching of gradient encoding orientations; however, it is limited by low spatial resolution and image distortions. Multi‐shot acquisition strategies could achieve higher resolution and image fidelity but increase the vulnerability to motion artifacts and phase variations related to cardiac pulsations from shot to shot. We use prospective motion correction with optical markerless motion tracking to remove artifacts and reduce image blurring due to bulk motion, combined with locally low‐rank regularization to correct for remaining artifacts due to shot‐to‐shot phase variations.
Results
The approach was evaluated on healthy adult volunteers at 3 Tesla under different motion patterns. In multi‐shot DWI, image blurring due to motion with 20 mm translations and 30° rotations was successfully removed by prospective motion correction, and aliasing artifacts caused by shot‐to‐shot phase variations were addressed by locally low‐rank regularization. The ability of prospective motion correction to preserve the orientational information in DTI without requiring a reorientation of the b‐matrix is highlighted.
Conclusion
The described technique is proved to hold valuable potential for mapping brain diffusivity and connectivity at high resolution for studies in subjects/cohorts where motion is common, including neonates, pediatrics, and patients with neurological disorders.
This review seeks to summarize diffusion tensor imaging (DTI) studies that have evaluated structural changes attributed to the mechanisms of mild traumatic brain injury (mTBI) in adult civilian, ...military, and athlete populations. Articles from 2002 to 2016 were retrieved from PubMed/MEDLINE, EBSCOhost, and Google Scholar, using a Boolean search string containing the following terms: “diffusion tensor imaging”, “diffusion imaging”, “DTI”, “white matter”, “concussion”, “mild traumatic brain injury”, “mTBI”, “traumatic brain injury”, and “TBI”. We added studies not identified by this method that were found via manually-searched reference lists. We identified 86 eligible studies from English-language journals using, adult, human samples. Studies were evaluated based on duration between injury and DTI assessment, categorized as acute, subacute/chronic, remote mTBI, and repetitive brain trauma considerations. Since changes in brain structure after mTBI can also be affected by other co-occurring medical and demographic factors, we also briefly review DTI studies that have addressed socioeconomic status factors (SES), major depressive disorder (MDD), and attention-deficit hyperactivity disorder (ADHD). The review describes population-specific risks and the complications of clinical versus pathophysiological outcomes of mTBI. We had anticipated that the distinct population groups (civilian, military, and athlete) would require separate consideration, and various aspects of the study characteristics supported this. In general, study results suggested widespread but inconsistent differences in white matter diffusion metrics (primarily fractional anisotropy FA, mean diffusivity MD, radial diffusivity RD, and axial diffusivity AD) following mTBI/concussion. Inspection of study designs and results revealed potential explanations for discrepant DTI findings, such as control group variability, analytic techniques, the manner in which regional differences were reported, and the presence or absence of persistent functional disturbances. DTI research in adult mTBI would benefit from more standardized imaging and analytic approaches. We also found significant overlap in white matter abnormalities reported in mTBI with those commonly affected by SES or the presence of MDD and ADHD. We conclude that DTI is sensitive to a wide range of group differences in diffusion metrics, but that it currently lacks the specificity necessary for meaningful clinical application. Properly controlled longitudinal studies with consistent and standardized functional outcomes are needed before establishing the utility of DTI in the clinical management of mTBI and concussion.
Morphological processing, the ability to extract information about word structure, is an essential component of reading. Functional MRI studies have identified several cortical regions involved in ...morphological processing, but the white matter pathways that support this skill remain unknown. Here, we examine the relationship between behavioral measures of morphological processing and microstructural properties of white matter pathways. Using diffusion MRI (dMRI), we identified the major ventral and dorsal reading pathways in a group of 45 adult English readers. The same participants completed a behavioral battery that included a morphological task and measures of phonological and orthographic processing. We found significant correlations between morphological processing skill and microstructural properties of the ventral, but not dorsal, pathways. These correlations were detected primarily in the left hemisphere, and remained significant after controlling for phonological or orthographic measures, suggesting some level of cognitive specificity. Morphological processing of written words thus appears to rely on ventral pathways, primarily in the left hemisphere. This finding supports the contribution of morphological processing to lexical access and comprehension of complex English words.
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