white matter tracts
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Neurology ◽  
2022 ◽  
Vol 98 (2) ◽  
pp. e107-e114
Author(s):  
Sadhvi Saxena ◽  
Zafer Keser ◽  
Chris Rorden ◽  
Leonardo Bonilha ◽  
Julius Fridriksson ◽  
...  

Background and ObjectivesHemispatial neglect is a heterogeneous and complex disorder that can be classified by frame of reference for “left” vs “right,” including viewer-centered neglect (VCN, affecting the contralesional side of the view), stimulus-centered neglect (SCN, affecting the contralesional side of the stimulus, irrespective of its location with respect to the viewer), or both. We investigated the effect of acute stroke lesions on the connectivity of neural networks that underlie VCN or SCN.MethodsA total of 174 patients within 48 hours of acute right hemispheric infarct underwent a detailed hemispatial neglect assessment that included oral reading, scene copy, line cancellation, gap detection, horizontal line bisection tests, and MRI. Each patient's connectivity map was generated. We performed a linear association analysis between network connectivity strength and continuous measures of neglect to identify lesion-induced disconnections associated with the presence or severity of VCN and SCN. Results were corrected for multiple comparisons.ResultsAbout 42% of the participants with right hemisphere stroke had at least one type of neglect. The presence of any type of neglect was associated with lesions to tracts connecting the right inferior parietal cortex, orbitofrontal cortex, and right thalamus to other right-hemispheric structures. VCN only was strongly associated with tracts connecting the right putamen to other brain regions and tracts connecting right frontal regions with other brain regions. The presence of both types of neglect was most strongly associated with tracts connecting the right inferior and superior parietal cortex to other brain regions and those connecting left or right mesial temporal cortex to other brain regions.DiscussionOur study provides new evidence for the specific white matter tracts where disruption can cause hemispatial neglect in a relatively large number of participants and homogeneous time after onset. We obtained MRI and behavioral testing acutely, before the opportunity for rehabilitation or substantial recovery.Classification of EvidenceThis study provides Class II evidence that damage to specific white matter tracts identified on MRI are associated with the presence of neglect following right hemispheric stroke.


2021 ◽  
Author(s):  
Alberto Lazari ◽  
Piergiorgio Salvan ◽  
Lennart Verhagen ◽  
Michiel Cottaar ◽  
Daniel Papp ◽  
...  

Abstract Myelination has been increasingly implicated in the function and dysfunction of the adult human brain. Although it is known that axon myelination shapes axon physiology in animal models, it is unclear whether a similar principle applies in the living human brain, and at the level of whole axon bundles in white matter tracts. Here, we hypothesised that in humans, cortico-cortical interactions between two brain areas may be shaped by the amount of myelin in the white matter tract connecting them. As a test bed for this hypothesis, we use a well-defined interhemispheric premotor-to-motor circuit. We combined TMS-derived physiological measures of cortico-cortical interactions during action reprogramming with multimodal myelin markers (MT, R1, R2* and FA), in a large cohort of healthy subjects. We found that physiological metrics of premotor-to-motor interaction are broadly associated with multiple myelin markers, suggesting interindividual differences in tract myelination may play a role in motor network physiology. Moreover, we also demonstrate that myelination metrics link indirectly to action switching by influencing local primary motor cortex dynamics. These findings suggest that myelination levels in white matter tracts may influence millisecond-level cortico-cortical interactions during tasks. They also unveil a link between the physiology of the motor network and the myelination of tracts connecting its components, and provide a putative mechanism mediating the relationship between brain myelination and human behaviour.


2021 ◽  
Author(s):  
Renata Basso Cupertino ◽  
Bruna Santos da Silva ◽  
Jaqueline Bohrer Schuch ◽  
Cibele Edom Bandeira ◽  
Maria Eduarda Tavares ◽  
...  

Abstract The Synaptotagmin-1 encoding gene (SYT1) is a key regulator of neurotransmitter release and is associated with cognitive and psychiatric phenotypes in GWAS, and with ADHD in single-gene studies, raising the need for dissecting possible cross-trait effects on clinical and brain phenotypes. Inferences about white matter microstructure can be made by diffusion-tensor imaging (DTI), which makes this method a promising tool in the understanding of biological changes that underpin cognitive functions and brain disorders. Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder that affects multiple functioning domains, highly overlapping with other psychiatric disorders, and known to involve white matter abnormalities and neurotransmission dysfunction. Using a set-based analysis, the present study investigates how genetic variants within SYT1 might affect brain white matter at a cellular level using DTI in adults with ADHD (n = 85). The combined effect of all measured variations in the gene (i.e., 468 variants) was evaluated concerning specific white matter tracts. Set-based analysis was performed in PLINK software and followed by in silico analysis of all variants included in the study. SYT1 gene was nominally associated with white matter changes in two important tracts: forceps major and inferior fronto-occipital fasciculus. In addition, two regions within the SYT1 have more consistent associations with different white matter tracts. These findings endorse the involvement of SYT1 on psychiatric phenotypes and suggest that white matter tracts underlie this complex relationship.


2021 ◽  
Vol 13 ◽  
Author(s):  
Ying Wei ◽  
Caihong Wang ◽  
Jingchun Liu ◽  
Peifang Miao ◽  
Sen Wei ◽  
...  

Neurological deficits after stroke are closely related to white matter microstructure damage. However, secondary changes in white matter microstructure after pontine infarction (PI) in the whole brain remain unclear. This study aimed to investigate the correlation of diffusion kurtosis imaging (DKI)-derived diffusion and kurtosis parameters of abnormal white matter tracts with behavioral function in patients with chronic PI. Overall, 60 patients with unilateral chronic PI (33 patients with left PI and 27 patients with right PI) and 30 normal subjects were recruited and underwent DKI scans. Diffusion parameters derived from diffusion tensor imaging (DTI) and DKI and kurtosis parameters derived from DKI were obtained. Between-group differences in multiple parameters were analyzed to assess the changes in abnormal white matter microstructure. Moreover, we also calculated the sensitivities of different diffusion and kurtosis parameters of DTI and DKI for identifying abnormal white matter tracts. Correlations between the DKI-derived parameters in secondary microstructure changes and behavioral scores in the PI were analyzed. Compared with the NC group, both left PI and right PI groups showed more extensive perilesional and remote white matter microstructure changes. The DKI-derived diffusion parameters showed higher sensitivities than did the DTI-derived parameters. Further, DKI-derived diffusion and kurtosis parameters in abnormal white matter regions were correlated with impaired motor and cognitive function in patients with PI. In conclusion, PI could lead to extensive white matter tracts impairment in perilesional and remote regions. Further, the diffusion and kurtosis parameters could be complementary for identifying comprehensive tissue microstructural damage after PI.


2021 ◽  
Vol 17 (S5) ◽  
Author(s):  
Andreana Benitez ◽  
Jens H. Jensen ◽  
Maria F. Falangola ◽  
Maria Vittoria Spampinato ◽  
William J. Rieter ◽  
...  

2021 ◽  
Vol 17 (S1) ◽  
Author(s):  
Derek B Archer ◽  
Elizabeth E. Moore ◽  
Ujwala Pamidimukkala ◽  
Niranjana Shashikumar ◽  
Kimberly R. Pechman ◽  
...  

2021 ◽  
Author(s):  
Kadi Vaher ◽  
Paola Galdi ◽  
Manuel Blesa ◽  
Gemma Sullivan ◽  
David Q Stoye ◽  
...  

Preterm birth is closely associated with diffuse white matter dysmaturation inferred from diffusion MRI and neurocognitive impairment in childhood. Diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) are distinct dMRI modalities, yet metrics derived from these two methods share variance across tracts. This raises the hypothesis that dimensionality reduction approaches may provide efficient whole-brain estimates of white matter microstructure that capture (dys)maturational processes. To investigate the optimal model for accurate classification of generalised white matter dysmaturation in preterm infants we assessed variation in DTI and NODDI metrics across 16 major white matter tracts using principal component analysis and structural equation modelling, in 79 term and 141 preterm infants at term equivalent age. We used logistic regression models to evaluate performances of single-metric and multimodality general factor frameworks for efficient classification of preterm infants based on variation in white matter microstructure. Single-metric general factors from DTI and NODDI capture substantial shared variance (41.8-72.5%) across 16 white matter tracts, and two multimodality factors captured 93.9% of variance shared between DTI and NODDI metrics themselves. General factors associate with preterm birth and a single model that includes all seven DTI and NODDI metrics provides the most accurate prediction of microstructural variations associated with preterm birth. This suggests that despite global covariance of dMRI metrics in neonates, each metric represents information about specific (and additive) aspects of the underlying microstructure that differ in preterm compared to term subjects.


Author(s):  
Kendra L. Furber ◽  
R. J. Scott Lacombe ◽  
Sally Caine ◽  
Merlin P. Thangaraj ◽  
Stuart Read ◽  
...  

Author(s):  
AC Friesen ◽  
SA Detombe ◽  
P Doyle-Pettypiece ◽  
H Haddad ◽  
W Ng ◽  
...  

Background: Degenerative cervical myelopathy is characterized by progressive compression of the spinal cord resulting in debilitating loss of dexterity, independent ambulation, and sphincter control. Diffusion tensor imaging (DTI) has shown that, compared to healthy controls, myelopathy patients have decreased integrity of the corticospinal tracts and corpus callosum (Bernabeu-Sanz et al, 2020). Methods: Twenty-six myelopathy patients consented to cerebral diffusion tensor imaging (3 Tesla, 32 directions, b=1000) preoperatively, as well as 6-weeks, 12-weeks, and 6-months postoperatively. Average mean diffusivity (MD), fractional anisotropy (FA), radial diffusivity (RD), and axial diffusivity (AD) were measured in the corticospinal tracts, forceps major, and forceps minor. Results: Both MD and RD decreased from 6-12 weeks postoperatively in the right corticospinal tract. The forceps major of the corpus callosum showed an initial postoperative increase in MD followed by a subsequent increase in FA and decrease in RD 3-6 months postoperatively. The AD of the forceps major increased both immediately and 3-6 months postoperatively. Conclusions: Changes in microstructural integrity of the corticospinal tract and forceps major over the postoperative recovery period suggest a pattern of recovery in myelopathy patients. This study is the first to report postoperative DTI changes in myelopathy-relevant white matter tracts in the brain.


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