Correlation of white matter diffusivity and anisotropy with age during childhood and adolescence: a cross-sectional diffusion-tensor MR imaging study

Cognitive modules utilized for narrative comprehension in children: a functional magnetic resonance imaging study

The ability to comprehend narratives constitutes an important component of human development and experience. The neural correlates of auditory narrative comprehension in children were investigated in a large-scale functional magnetic resonance imaging (fMRI) study involving 313 subjects ages 5-18. Using group independent component analysis (ICA), bilateral task-related components were found comprising the primary auditory cortex, the mid-superior temporal gyrus, the hippocampus, the angular gyrus, and medial aspect of the parietal lobule (precuneus/posterior cingulate). In addition, a right-lateralized component was found involving the most posterior aspect of the superior temporal gyrus, and a left-lateralized component was found comprising the inferior frontal gyrus (including Broca's area), the inferior parietal lobule, and the medial temporal gyrus. Using a novel data-driven analysis technique, increased task-related activity related to age was found in the components comprising the mid-superior temporal gyrus (Wernicke's area) and the posterior aspect of the superior temporal gyrus, while decreased activity related to age was found in the component comprising the angular gyrus. The results are discussed in light of recent hypotheses involving the functional segregation of Wernicke's area and the specific role of the mid-superior temporal gyrus in speech comprehension.

Quantitative diffusion tensor imaging in cerebral palsy due to periventricular white matter injury

Periventricular white matter injury (PWI) is a major form of brain injury observed in congenital hemiparesis. The aim of this study is to determine the usefulness of diffusion tensor imaging (DTI) and fibre tracking in delineating the primary and secondary degenerative changes in cerebral white matter and deep grey matter in patients with spastic cerebral palsy due to PWI and to look for any possible reorganization of the axonal architecture. Five hemiparetic cerebral palsy patients (median age 14 years) with known PWI were prospectively studied with DTI of the brain at 1.5T and quantitatively compared with five age and sex matched controls. Fibre tracts for various corticofugal, thalamocortical and association tracts were generated and analysed for the DTI fibre count and for diffusion parameters. A region of interest based analysis was performed for the directionally averaged mean diffusivity (D(av)) and fractional anisotropy (FA) values in various white matter locations in the brain and the brainstem and in the deep grey matter nuclei. Group statistics were performed for these parameters using Mann-Whitney U-test comparing the affected sides in patients with either side in controls and the unaffected side in hemiparetics. There was significant reduction in DTI fibre count on the lesional side involving corticospinal tract (CST), corticobulbar tract (CBT) and superior thalamic radiation in the patient group compared with controls. Also there was an increase in DTI fibre count in the unaffected side of the hemiparetic patients in CST and CBT, which reached statistical significance only in CBT. The corpus callosum, cingulum, superior longitudinal fasciculus and middle cerebellar peduncle failed to show any significant change. ROI measurements on the primary site of white matter lesion and the thalamus revealed a significant increase in D(av) and decrease in FA, suggesting primary degeneration. The CST in the brainstem, the body of corpus callosum and the head of caudate and lentiform nuclei showed features of secondary degeneration on the affected side. The CST on the unaffected side of hemiparetics was found to have a significant decrease in D(av) and an increase in FA. Thus the degeneration of various motor and sensory pathways, as well as deep grey matter structures, appears to be important in determining the pathophysiological mechanisms in patients with congenital PWI. Also evidence suggesting the reorganization of sensorimotor tracts in the unaffected side of spastic hemiparetic patients was noted.

Diffusion tensor imaging in lissencephaly

Lissencephaly is a rare brain malformation characterized histologically by arrested neuronal migration such that the brain resembles that of a fetus before 23-24 weeks gestation. We studied a neonate with lissencephaly by using diffusion tensor imaging and suggest the dysplastic densely cellular layer IV is visible as a band of anisotropic diffusion. Fiber tracking showed lack of connectivity between the cortex and deep white matter and an abnormal limbic system.

Children's reading performance is correlated with white matter structure measured by diffusion tensor imaging

We investigated the white matter structure in children (n = 14) with a wide range of reading performance levels using diffusion tensor imaging (DTI), a form of magnetic resonance imaging. White matter structure in a left temporo-parietal region that had been previously described as covarying with reading skill in adult readers also differs between children who are normal and poor readers. Specifically, the white matter structure measured using fractional anisotropy (FA) and coherence index (CI) significantly correlated with behavioral measurements of reading, spelling, and rapid naming performance. In general, lower anisotropy and lower coherence were associated with lower performance scores. Although the magnitude of the differences in children are smaller than those in adults, the results support the hypothesis that the structure of left temporoparietal neural pathways is a significant component of the neural system needed to develop fluent reading.

Cortical reorganization in children with unilateral sensorineural hearing loss

Previous studies have shown evidence of cortical reorganization following unilateral sensorineural hearing loss (USNHL). In addition, study participants with right USNHL have shown greater deficits in academic and language performance compared with those with left USNHL. A preliminary functional magnetic resonance imaging investigation was performed on a small cohort of participants, four with left USNHL and four with right USNHL, using the paradigm of listening to random tones. While the participants with left USNHL displayed greater activation in the right superior temporal gyrus, those with right USNHL displayed greater activation in the left inferior frontal area immediately anterior to the superior temporal gyrus. The results provide preliminary evidence of disparate neural circuitry supporting auditory processing in participants with left and right USNHL.

White matter development during childhood and adolescence: a cross-sectional diffusion tensor imaging study

Maturation of brain white matter pathways is an important factor in cognitive, behavioral, emotional and motor development during childhood and adolescence. In this study, we investigate white matter maturation as reflected by changes in anisotropy and white matter density with age. Thirty-four children and adolescents aged 6-19 years received diffusion-weighted magnetic resonance imaging scans. Among these, 30 children and adolescents also received high-resolution T1-weighed anatomical scans. A linear regression model was used to correlate fractional anisotropy (FA) values with age on a voxel-by-voxel basis. Within the regions that showed significant FA changes with age, a post hoc analysis was performed to investigate white matter density changes. With increasing age, FA values increased in prefrontal regions, in the internal capsule as well as in basal ganglia and thalamic pathways, the ventral visual pathways, and the corpus callosum. The posterior limb of the internal capsule, intrathalamic connections, and the corpus callosum showed the most significant overlaps between white matter density and FA changes with age. This study demonstrates that during childhood and adolescence, white matter anisotropy changes in brain regions that are important for attention, motor skills, cognitive ability, and memory. This typical developmental trajectory may be altered in individuals with disorders of development, cognition and behavior.

MR quantitation of volume and diffusion changes in the developing brain

BACKGROUND AND PURPOSE

Brain volume and diffusion change during maturation. Quantitation of these changes may be helpful in understanding normal brain development. We used diffusion-weighted imaging to characterize the volumetric and diffusion changes in vivo.

METHODS

We recruited 30 pediatric volunteers (aged 1 month-17 years; 14 male, 16 female). Diffusion was measured in three orthogonal directions with a b value of 1000 s/mm2. The diffusion parameters from the entire brain were calculated and fitted to a triple gaussian model. In addition, region-of-interest measurements were made in caudate, thalamus, genu and splenium of the corpus callosum, and periventricular white matter (PVWM). The brain volume was measured by counting pixels and by using the model.

RESULTS

Water diffusion of the whole brain, caudate, thalamus, genu and splenium of the corpus callosum, and PVWM decreased during maturation, with the most significant change within the first 2 years. Robust negative correlations were found between age and the measured average diffusion constant (Dav) values in each of the measured locations (P <.005). Volumes of different cerebral compartments and the total intracranial volume (ICV) increased rapidly during the first 2 years of life and then had a slower growth process through adolescence. Age was correlated with the ICV and the volume of each brain compartment (P <.005).

CONCLUSION

Brain diffusion decreases and brain volume increases during maturation, with the most significant changes occurring within the first 2 years of life. The brain model used in this study provides a good estimate of the increasing brain volume.

The emergence of consequential thought: evidence from neuroscience

The ability to think counterfactually about the consequence of one's actions represents one of the hallmarks of the development of complex reasoning skills. The legal system places a great emphasis on this type of reasoning ability as it directly relates to the degree to which individuals may be judged liable for their actions. In the present paper, we review both behavioural and neuroscientific data exploring the role that counterfactual thinking plays in reasoning about the consequences of one's actions, especially as it pertains to the developing mind of the adolescent. On the basis of assimilation of both behavioural and neuroscientific data, we propose a brain-based model that provides a theoretical framework for understanding the emergence of counterfactual reasoning ability in the developing mind.

Maturation of white matter is associated with the development of cognitive functions during childhood

In the human brain, myelination of axons continues until early adulthood and is thought to be important for the development of cognitive functions during childhood. We used diffusion tensor MR imaging and calculated fractional anisotropy, an indicator of myelination and axonal thickness, in children aged between 8 and 18 years. Development of working memory capacity was positively correlated with fractional anisotropy in two regions in the left frontal lobe, including a region between the superior frontal and parietal cortices. Reading ability, on the other hand, was only correlated with fractional anisotropy in the left temporal lobe, in the same white matter region where adults with reading disability are known to have lower fractional anisotropy. Both the temporal and the frontal regions were also correlated with age. These results show that maturation of white matter is an important part of brain maturation during childhood, and that maturation of relatively restricted regions of white matter is correlated with development of specific cognitive functions.

Segmentation of subcomponents within the superior longitudinal fascicle in humans: a quantitative, in vivo, DT-MRI study

Previous research in non-human primates has shown that the superior longitudinal fascicle (SLF), a major intrahemispheric fiber tract, is actually composed of four separate components. In humans, only post-mortem investigations have been available to examine the trajectory of this tract. This study evaluates the hypothesis that the four subcomponents observed in non-human primates can also be found in the human brain using in vivo diffusion tensor magnetic resonance imaging (DT-MRI). The results of our study demonstrated that the four subdivisions could indeed be identified and segmented in humans. SLF I is located in the white matter of the superior parietal and superior frontal lobes and extends to the dorsal premotor and dorsolateral prefrontal regions. SLF II occupies the central core of the white matter above the insula. It extends from the angular gyrus to the caudal-lateral prefrontal regions. SLF III is situated in the white matter of the parietal and frontal opercula and extends from the supramarginal gyrus to the ventral premotor and prefrontal regions. The fourth subdivision of the SLF, the arcuate fascicle, stems from the caudal part of the superior temporal gyrus arches around the caudal end of the Sylvian fissure and extends to the lateral prefrontal cortex along with the SLF II fibers. Since DT-MRI allows the precise definition of only the stem portion of each fiber pathway, the origin and termination of the subdivisions of SLF are extrapolated from the available data in experimental material from non-human primates.

BOLD fMRI signal increases with age in selected brain regions in children

To determine whether the BOLD signal used in fMRI is age dependent in childhood, 332 healthy children (age 4.9-18.9 years) performed tasks in a periodic block design during 3 T fMRI: (1) a verb generation task interleaved with a finger tapping task; (2) a word-picture matching task interleaved with an image discrimination task. Significant correlations between percent signal change in BOLD effect and age occurred in left Broca's, middle frontal, Wernicke's, and inferior parietal regions, and anterior cingulate during the verb generation task; in precentral, postcentral, middle frontal, supplementary motor, and precuneus regions during the finger tapping task; and in bilateral lingula gyri during the word-picture matching task. Thus, BOLD effect increases with age in children during sensorimotor and language tasks.

3 Tesla magnetic resonance imaging of the brain in newborns

While it has been hypothesized that brain development is abnormal in schizophrenia and other neurodevelopmental disorders, there have been few attempts to study very early brain development in children. Twenty unsedated healthy newborns underwent 3 Tesla magnetic resonance imaging (MRI), including diffusion tensor imaging (DTI). The left ventricle was significantly larger than the right; females had significantly larger ventricles than males. Fractional anisotropy (FA) increased significantly with gestational age in the genu and splenium of the corpus callosum. It is feasible to study brain development in unsedated newborns using 3 T MRI.

White Matter Asymmetry in the Human Brain: A Diffusion Tensor MRI Study

Language ability and handedness are likely to be associated with asymmetry of the cerebral cortex (grey matter) and connectivity (white matter). Grey matter asymmetry, most likely linked to language has been identified with voxel-based morphometry (VBM) using T(1)-weighted images. Differences in white matter obtained with this technique are less consistent, probably due to the relative insensitivity of the T(1) contrast to the ultrastructure of white matter. Furthermore, previous VBM studies failed to find differences related to handedness in either grey or white matter. We revisited these issues and investigated two independent groups of subjects with diffusion-tensor imaging (DTI) for asymmetries in white matter composition. Using voxel-based statistical analyses an asymmetry of the arcuate fascicle was observed, with higher fractional anisotropy in the left hemisphere. In addition, we show differences related to handedness in the white matter underneath the precentral gyrus contralateral to the dominant hand. Remarkably, these findings were very robust, even when investigating small groups of subjects. This highlights the sensitivity of DTI for white matter tissue differences, making it an ideal tool to study small patient populations.

Reduced frontal white matter integrity in early-onset schizophrenia: a preliminary study

BACKGROUND

Research suggests that brain frontal white matter (WM) might be qualitatively altered in adolescents with early onset schizophrenia (EOS). Diffusion tensor imaging provides a relatively new approach for quantifying possible connectivity of WM in vivo.

METHODS

Diffusion tensor imaging was used to examine the WM integrity of frontal regions at seven levels from 25 mm above to 5 mm below the anterior commissure-posterior commissure (AC-PC) plane. Three other regions were examined: the occipital region at the AC-PC plane and the genu and splenium of the corpus callosum. Fractional anisotropy was compared between 12 adolescents (nine male, 3 female) with EOS (onset of psychotic symptoms by age 18 years) and nine age-similar healthy comparison subjects (six male, 3 female).

RESULTS

Adolescents with EOS had significantly reduced fractional anisotropy in the frontal WM at the AC-PC plane in both hemispheres and in the occipital WM at the AC-PC plane in the right hemisphere.

CONCLUSIONS

These preliminary data support a hypothesis that alterations in brain WM integrity occur in adolescents with EOS. Abnormalities found in this study were similar to those reported in adults with chronic schizophrenia. Additional studies are needed to assess whether there is progression of WM abnormalities in schizophrenia.

Comparisons of Regional White Matter Diffusion in Healthy Neonates and Adults Performed with a 3.0-T Head-only MR Imaging Unit

PURPOSE

To evaluate the normal brains of adults and neonates for regional and age-related differences in apparent diffusion coefficient (ADC) and fractional anisotropy (FA).

MATERIALS AND METHODS

Eight healthy adults and 20 healthy neonates were examined with a 3.0-T head-only magnetic resonance (MR) imaging unit by using a single-shot diffusion-tensor sequence. Trace ADC maps, FA maps, directional maps of the putative directions of white matter (WM) tracts, and fiber-tracking maps were obtained. Regions of interest-eight in WM and one in gray matter (GM)-were predefined for the ADC and FA measurements. The Student t test was used to compare FA and ADC between adults and neonates, whereas the Tukey multiple-comparison test was used to compare FA and ADC in different brain regions in the adult and neonate groups.

RESULTS

A global elevation in ADC (P <.001) in both GM and WM and a reduction in FA (P <.001) in WM were observed in neonates as compared with these values in adults. In addition, significant regional variations in FA and ADC were observed in both groups. Regional variations in FA and ADC were less remarkable in adults, whereas neonates had consistently higher FA values and lower ADC values in the central WM as compared with these values in the peripheral WM. Fiber tracking revealed only major WM tracts in the neonates but fibers extending to the peripheral WM in the adults.

CONCLUSION

There were regional differences in FA and ADC values in the neonates; such variations were less remarkable in the adults.

Practical consideration for 3T imaging

In the past 10 to 15 years, 1.5T has been one of the most commonly used field strengths for day-to-day clinical operations. However, recent advances in high field technology and the increased availability of high field (> 1.5T) human scanners have opened the doors for a variety of exciting improvements in clinical and research applications of MR imaging. In particular, 3T has continued to gain wide acceptance as one of the main field strengths for clinical and research studies. Therefore, in this article the authors focus on the pros and cons of 3T imaging and comparisons between results obtained at 3T and 1.5T.

Variability of gray and white matter during normal development: a voxel-based MRI analysis

This study was aimed at investigating regional and local variability of brain tissue during normal human brain development. We investigated high-resolution MR-imaging data using SPM99 (Wellcome Department, University College London, UK). A pixel-wise variation coefficient of gray and white matter was calculated to visualize local variability. Data from 200 normal children (5-18 years) were analyzed. We found a profound interaction between variability of brain structures and normal development in both gray and white matter. Variability in gray and white matter shows regionally specific, age-related variations, possibly offering a new tool for the assessment of subtle brain abnormalities. Our results emphasize the necessity to take this variability into account when planning pediatric neuroimaging studies.

Assessing brain development using neurophysiologic and behavioral measures

One critical aspect of pediatric research is the assessment of outcome measures after treatment or intervention. Behavioral measures of physical growth, school achievement, and general intelligence have proven to be important scales for assessing gross developmental outcome and differences between pediatric treatment groups. However, more subtle and sophisticated measures may be required to assess finer grained differences in brain development at the structural and functional levels. Advances in noninvasive brain imaging techniques over the past decade have improved our ability to link specific cognitive functions to changes in brain structure and function in healthy infants and children. This paper highlights some of the ways that electrophysiologic and functional magnetic resonance imaging methods have been combined with behavioral measures of cognitive and emotional function to advance our understanding of brain-behavior relations. Such combined neurophysiologic and behavioral methods may help to identify the role specific interventions have on long-term developmental outcomes in childhood.

Diffusion tensor brain imaging findings at term-equivalent age may predict neurologic abnormalities in low birth weight preterm infants

BACKGROUND AND PURPOSE

Low birth weight preterm infants are at high risk of brain injury, particularly injury to the white matter. Diffusion tensor imaging is thought to be more sensitive than conventional MR imaging for detecting subtle white matter abnormalities. The objective of this study was to examine whether diffusion tensor imaging could detect abnormalities that may be associated with later neurologic abnormalities in infants with otherwise normal or minimally abnormal conventional MR imaging findings.

METHODS

We prospectively studied 137 low birth weight (<1800 g) preterm infants. Neonatal conventional MR imaging and diffusion tensor imaging were performed near term-equivalent age before discharge, and neurologic development of the infants was later followed up at 18 to 24 months of age.

RESULTS

Among the preterm infants who were fully studied, 63 underwent normal conventional MR imaging. Three of these infants developed cerebral palsy, and 10 others showed abnormal neurologic outcome. Diffusion tensor imaging results for these infants showed a significant reduction of fractional anisotropy in the posterior limb of the internal capsule in neurologically abnormal infants (including those with cerebral palsy) compared with control preterm infants with normal neurologic outcomes.

CONCLUSION

These results suggest that neonatal diffusion tensor imaging may allow earlier detection of specific anatomic findings of microstructural abnormalities in infants at risk for neurologic abnormalities and disability. The combination of conventional MR imaging and diffusion tensor imaging may increase the predictive value of neonatal MR imaging for later neurologic outcome abnormalities and may become the basis for future interventional clinical studies to improve outcomes.

Isotropic apparent diffusion coefficient mapping of postnatal cerebral development

Diffusion-weighted imaging (DWI) allows us to image the motion of tissue water. This has been used to demonstrate acute ischaemia. Diffusion imaging is also sensitive to water movement along neuronal tracts. Our objective was to map brain maturation in vivo using maps of apparent diffusion coefficient (ADC). We studied 22 children without neurological disease aged between 2 and 720 days. MRI was performed at 1.5 tesla. Multislice single-shot echoplanar DWI was performed at b 0 and 1000 s/mm(2). ADC maps were generated automatically and measurements were performed in the basal ganglia, frontal and temporal white matter and the pons. There was a decrease over time in water diffusion in the areas examined, most marked in the frontal (0.887-1.898 x 10(-3) mm(2)/s) and temporal (1.077-1.748 x 10(-3) mm(2)/s)lobes. There was little change, after an initial decrease, in the basal ganglia (0.690-1.336 x 10(-3) mm(2)/s). There was a difference in water diffusion between the anterior (0.687-1.581 x 10(-3) mm(2)/s) and posterior (0.533-1.393 x 10(-3) mm(2)/s) pons. These changes correlate well with those observed in progressive myelination: the increased water content probably reflects incomplete myelination and the decrease with time in water motion reflects the increase in myelinated brain.

Diffusion tensor imaging in cases of adrenoleukodystrophy: preliminary experience as a marker for early demyelination?

BACKGROUND AND PURPOSE

Diffusion tensor imaging measures the proton diffusivity and preferential orientation of the diffusion tensor. X-linked adrenoleukodystrophy is a demyelinating disease for which therapy depends on the onset and extension of demyelination. We investigated the ability of diffusion tensor imaging to detect changes in the demyelinated lesions and in the normal appearing white matter.

METHODS

Diffusion tensor imaging of three related boys with X-linked adrenoleukodystrophy and seven age-matched control participants was performed. Isotropic diffusion (D') and fractional anisotropy (FA) values were determined in 18 regions of interest in the white matter of both hemispheres.

RESULTS

In all the demyelinated white matter areas, a pattern with increased D' and loss of FA was found. For example, mean D' was 1.772 x 10(-3)mm(2)/s in patient 2 with blindness and extensive demyelination of the occipital white matter and was 0.693 x 10(-3)mm(2)/s in control participants (P =.01). In the same region, mean FA was 0.103 (0.464 in control participants, P <.0001). Significant alterations of D' and FA were also observed in normal appearing white matter. For example, mean D' was 0.802 x 10(-3)mm(2)/s in the parietal white matter of patient 1 with no visible alterations on T2-weighted images (0.715 x 10(-3) mm(2)/s in control patients, P =.03), whereas mean FA was 0.320 (0.400 in control participants, P =.003).

CONCLUSION

Elevated D' and loss of FA revealed by diffusion tensor imaging are consistent with severe demyelination in patients with X-linked adrenoleukodystrophy. Significant alterations of D' and FA in normal appearing white matter may indicate early demyelination in areas that are not yet visibly altered on conventional MR images. Further evaluation in a larger series of patients and long-term study are needed.

Diffusion-weighted magnetic resonance imaging of cerebral white matter development

Diffusion-weighted magnetic resonance imaging (DWI) has become a sensitive tool to monitor white matter development. Different applications of diffusion-weighted techniques provide information about premyelinating, myelinating, and postmyelinating states of white matter maturation. Mirroring maturational processes on the cellular level, DWI has to be regarded as a morphological method as well as a functional instrument, giving insight into molecular processes during the formation of axons and myelin sheets and into the steric arrangement of white matter tracts the formation of which is strongly influenced by their function.

Disconnection of speech-relevant brain areas in persistent developmental stuttering

BACKGROUND

The neuronal basis of persistent developmental stuttering is unknown. The disorder could be related to a reduced left hemisphere dominance, which functional neuroimaging data suggest might lead to right hemispheric motor and premotor overactivation. Alternatively, the core deficit underlying stuttering might be located in the speech-dominant left hemisphere. Furthermore, magnetoencephalography study results show profound timing disturbances between areas involved in language preparation and execution in the left hemisphere, suggesting that persistent developmental stuttering might be related to impaired neuronal communication, possibly caused by a disruption of white matter fibre tracts. We aimed to establish whether disconnection between speech-related cortical areas was the structural basis of persistent developmental stuttering.

METHODS

We analysed the speech of 15 people with persistent developmental stuttering and 15 closely matched controls for the percentage of syllables stuttered. We used diffusion tensor imaging to assess participants' brain tissue structure, and used and two-sample t test to compare diffusion characteristics between groups.

FINDINGS

Diffusion characteristics of the group with persistent developmental stuttering and controls differed significantly immediately below the laryngeal and tongue representation in the left sensorimotor cortex (mean difference in fractional anisotropy 0.04 [95% CI 0.03-0.05]).

INTERPRETATION

Our findings show that persistent developmental stuttering results from disturbed timing of activation in speech-relevant brain areas, and suggest that right hemisphere overactivation merely reflects a compensatory mechanism, analogous to right hemisphere activation in aphasia.

Differences in white matter architecture between musicians and non-musicians: a diffusion tensor imaging study

Previous studies found structural brain differences between musicians and non-musicians. In order to determine possible differences in white matter architecture, diffusion tensor imaging was performed on five adult subjects with musical training since early childhood, and seven adult controls. The musicians displayed significantly greater fractional anisotropy (FA) in the genu of the corpus callosum, while significantly less FA was found in the corona radiata and the internal capsule bilaterally. Further areas also showed significant differences. We hypothesize that these changes are due to the cognitive and motor effects, respectively, of musical training.