Differential relationships between brain structure and dual task walking in young and older adults

Almost 25% of all older adults experience difficulty walking. Mobility difficulties for older adults are more pronounced when performing a simultaneous cognitive task while walking (i.e., dual task walking). Although it is known that aging results in widespread brain atrophy, few studies have integrated across more than one neuroimaging modality to comprehensively examine the structural neural correlates that may underly dual task walking in older age. We collected spatiotemporal gait data during single and dual task walking for 37 young (18-34 years) and 23 older adults (66-86 years). We also collected T1-weighted and diffusion-weighted MRI scans to determine how brain structure differs in older age and relates to dual task walking. We addressed two aims: 1) to characterize age differences in brain structure across a range of metrics including volumetric, surface, and white matter microstructure; and 2) to test for age group differences in the relationship between brain structure and the dual task cost (DTcost) of gait speed and variability. Key findings included widespread brain atrophy for the older adults, with the most pronounced age differences in brain regions related to sensorimotor processing. We also found multiple associations between regional brain atrophy and greater DTcost of gait speed and variability for the older adults. The older adults showed a relationship of both thinner temporal cortex and shallower sulcal depth in the frontal, sensorimotor, and parietal cortices with greater DTcost of gait. Additionally, the older adults showed a relationship of ventricular volume and superior longitudinal fasciculus free-water corrected axial and radial diffusivity with greater DTcost of gait. These relationships were not present for the young adults. Stepwise multiple regression found sulcal depth in the left precentral gyrus, axial diffusivity in the superior longitudinal fasciculus, and sex to best predict DTcost of gait speed, and cortical thickness in the superior temporal gyrus to best predict DTcost of gait variability for older adults. These results contribute to scientific understanding of how individual variations in brain structure are associated with mobility function in aging. This has implications for uncovering mechanisms of brain aging and for identifying target regions for mobility interventions for aging populations.

Connectivity of the Superior Longitudinal Fasciculus II and Executive Function in Children with ADHD

Attention-deficit hyperactivity disorder (ADHD) is a common childhood neurodevelopmental disorder marked by inattention, hyperactivity, and impulsiveness. The importance of the Superior Longitudinal Fasciculus II (SLFII), a white matter tract connecting the frontal and parietal regions, to developing executive function has not been established in children who typically have executive function deficits. The present study explored the association between diffusion properties of the SLFII and developing executive function in young children diagnosed with ADHD. A dataset with the performance on the NIH Toolbox Card Sort and the NIH Toolbox Flanker, two executive function tasks, in 59 4-7-year-old children was used, and diffusion-weighted magnetic resonance imaging scans were used to quantify the white matter properties of the bilateral SLFII. The results showed that there was an association between age and performance on the Flanker and Card Sort tasks. As age increased, performance also improved. There was no significant association between white matter properties of the SLFII, birth sex, and the Card Sort and Flanker tasks. As the first study to explore this association in children of this age with ADHD, this result was unexpected suggesting that it may be the case that it is too early in development to detect a strong association. The findings inform contemporary and future investigations into the brain-behavior relations between SLFII and executive function in children with ADHD. With further research, neuroimaging could become a potential diagnostic biomarker for predicting executive function impairments and ADHD symptoms in young children, potentially altering treatment outcomes.

White matter integrity in patients with classic trigeminal neuralgia: a multi-node automated fiber tract quantification study

Objective To study the characteristics of point-by-point destruction of white matter tracts in patients using automated fiber tract quantification (AFQ). Methods Thirty-four classic trigeminal neuralgia (CTN) patients and 34 healthy control (HC) subjects underwent 3.0 T diffusion tensor magnetic resonance imaging and T1-weighted imaging. The fractional anisotropy (FA) and mean diffusivity (MD) of 100 nodes of 20 fiber tracts were analyzed by AFQ, and the correlations of the FA and MD with the visual analogue scale (VAS) pain score were assessed. Results The FA values of the left thalamic radiation (middle segment), left corticospinal tract, callosum forceps minor, and right uncinate fasciculus were significantly lower in CTN patients than in the HC group. The MD of the left thalamic tract (middle segment), left corticospinal tract, right superior longitudinal fasciculus, and left superior longitudinal fasciculus (anterior segment) were significantly higher in the CTN group. Additionally, the VAS pain score in CTN patients was positively correlated with FA and negatively correlated with MD. Conclusion Specific fiber tract nodes were damaged in CTN patients, which was related to the VAS pain score. Multi-node quantitative studies of fiber tract damage are valuable for understanding the white matter tract damage pattern in CTN patients.

P03.05 The use of subcortical intraoperative electrical stimulation mapping for assessment of executive functions: A summary of the evidence so far

BACKGROUND Over the past years, the functional subcortical architecture of the brain has been increasingly acknowledged in neurosurgical planning. A method to study anatomo-functional correlations is direct electrical stimulation (DES). DES is widely used by neurosurgeons and considered as a reliable tool to minimize the occurrence of permanent postoperative motor, language and visual deficits. In recent years, DES has also been used for mapping of other cognitive functions, such as executive functions. MATERIAL AND METHODS We systematically summarized the evidence so far from DES studies on subcortical pathways that are involved in the following three executive functions: (1) inhibitory control, (2) working memory and (3) cognitive flexibility. RESULTS We only found twelve articles that reported on intraoperative electrical stimulation of white matter pathways to map executive functions and explicitly clarified which subcortical tract was stimulated. The results indicate that the second branch of the right superior longitudinal fasciculus (SLF-II) is involved in inhibitory control, the first branch of the right superior longitudinal fasciculus (SLF-I) and the third branch of the left superior longitudinal fasciculus (SLF-III) are involved in working memory and the cingulum is involved in cognitive flexibility. CONCLUSION We were unable to draw any specific conclusions, nor unequivocally established the pathways involved in executive functions due to heterogenous study characteristics, methods and tasks, and the limited number of studies that assessed these relationships. Clearly, neurosurgical groups are exploring novel methods to assess cognition during awake neurosurgery, but are far from consensus on indications and protocols, which complicated the comparison and summarization of findings. We will discuss possible approaches for future research to obtain converging and more definite evidence for the involvement of subcortical pathways in specific executive functions.

Right fronto-parietal networks mediate the neurocognitive benefits of enriched environments.

Exposure to enriched environments (EE) throughout a lifetime, providing so called reserve, protects against cognitive decline in later years. It has been hypothesised that high levels of alertness necessitated by EE might strengthen the right fronto-parietal networks (FPN) to facilitate this neurocognitive resilience. We have previously shown that EE offset age-related deficits in selective attention by preserving grey matter within right fronto-parietal regions. Here, using neurite orientation dispersion and density imaging (NODDI), we examined the relationship between EE, microstructural properties of fronto-parietal white matter association pathways (three branches of the superior longitudinal fasciculus, SLF), structural brain health (atrophy), and attention (alertness, orienting and executive control) in a group of older adults. We show that EE is associated with a lower orientation dispersion index (ODI) within the right SLF1 which in turn mediates the relationship between EE and alertness, as well as grey- and white-matter atrophy. This suggests that EE may induce white matter plasticity (and prevent age-related dispersion of axons) within the right FPN to facilitate the preservation of neurocognitive health in later years.

Injuries in Left Corticospinal Tracts, Forceps Major, and Left Superior Longitudinal Fasciculus (Temporal) as the Quality Indicators for Major Depressive Disorder

At present, the etiology and pathogenesis of major depressive disorder (MDD) are still not clear. Studies have found that the risk of first-degree relatives of MDD is 2–3 times that of the general population. Diffusion tensor imaging (DTI) has been previously used to explore the pathogenesis of MDD. The purpose of this study is to explore the etiology of MDD by DTI and further to explore the correlation between its clinical characteristics and the structural changes of white matter in the brain. The study included 27 first-episode, drug-naive patients with MDD, 16 first-degree relatives without MDD, and 28 healthy control subjects with no family history of MDD (HC). Results showed that the fractional anisotropy (FA) differences among the three groups were mainly in the left anterior thalamic radiation (LATR), right anterior thalamic radiation (RATR), left corticospinal tracts (LCST), forceps major (FMa), right inferior longitudinal fasciculus (RILF), and left superior longitudinal fasciculus (temporal) (LSLF(T)). Among the 6 sites, LCST, FMa, and LSLF(T) showed significant differences between MDD and First-degree relatives compared to HC. MDD patients had significant emotional symptoms, somatic symptoms, and cognitive impairment. FMa FA was significantly positively correlated with delayed memory score ( r = 0.43 , P = 0.031 ), and RILF FA was significantly negatively correlated with the FSS score ( r = − 0.42 , P = 0.028 ). These results revealed that the white matter characteristics of MDD-susceptible patients were LCST, FMa, and LSLF(T) lesions, all of which may be quality indicators of MDD.

Abnormal Neurite Density and Orientation Dispersion in Frontal Lobe Link to Elevated Hyperactive/Impulsive Behaviors in Young Adults with Traumatic Brain Injury

Traumatic brain injury is a major public health concern. A significant proportion of individuals experience post-traumatic brain injury behavioral impairments, especially in attention and inhibitory control domains. Traditional diffusion-weighted MRI techniques, such as diffusion tensor imaging, have provided tools to assess white matter structural disruptions reflecting the long-term brain tissue alterations associated with traumatic brain injury. The recently developed neurite orientation dispersion and density imaging is a more advanced diffusion-weighted MRI modality, which provides more refined characterization of brain tissue microstructures by assessing the neurite orientation dispersion and neurite density properties. In this study, we investigated the morphometrical and microstructural alterations at chronic brain injury stage and their relationships with the functional outcomes. Neurite orientation dispersion and density imaging data from 44 young adults with chronic traumatic brain injury (ranging from 18 - 27 years of age; 23 males/21 females) who had no prior-traumatic brain injury history of attention deficits and/or hyperactivity and 45 group-matched normal controls (23 males /22 females) were collected. Maps of fractional anisotropy, neurite orientation dispersion index, and neurite density index were calculated. Vertex-wise and voxel-wise analyses were conducted for gray matter and white matter, respectively. Post-hoc region of interest-based analyses were also performed. Compared to the controls, the group of traumatic brain injury showed significantly increased orientation dispersion index in various gray matter regions and significantly decreased orientation dispersion index in several white matter regions. Brain-behavioral association analyses indicated that the reduced neurite density index of left precentral gyrus and the reduced orientation dispersion index of left superior longitudinal fasciculus were significantly associated with elevated hyperactive/impulsive symptoms in the patients with traumatic brain injury. These findings suggest that traumatic brain injury-induced chronic neurite orientation dispersion alterations of left superior longitudinal fasciculus and left precentral may significantly contribute to post-traumatic brain injury hyperactive/impulsive behaviors in young adults with traumatic brain injury.

Classification of Surgery-Related Language Impairments in Patients with Glioma Based on Tumor Locations

IntroductionMany patients with glioma experience surgery-related language impairment. This study developed a classification system to predict postoperative language prognosis.MethodsSixty-eight patients were retrospectively reviewed. Based on their location, tumors were subtyped as follows: I) inferior frontal lobe or precentral gyrus; II) posterior central gyrus or supramarginal gyrus (above the lateral fissure level); III) posterior region of the superior or middle temporal gyri or supramarginal gyrus (below the lateral fissure level); and IV) insular lobe. The distance from the tumor to the superior longitudinal fasciculus/arcuate fasciculus was calculated. The recovery of language function was assessed using the Western Aphasia Battery before surgery, and a comprehensive language test was conducted on the day of surgery; 3, 7, and 14 days later, and 3 months later.ResultsThirty-three patients experienced transient language impairment within 1 week of surgery. Fourteen patients had permanent language impairment. Type II tumors, shorter distance from the tumor to the posterior superior longitudinal fasciculus/arcuate fasciculus, and isocitrate dehydrogenase mutations were risk factors for surgery-related language impairment. Regarding the presence or absence of permanent surgery-related language impairments, the cut-off distance between the tumor and posterior superior longitudinal fasciculus/arcuate fasciculus was 2.75 mm.ConclusionsAccording to our classification, patients with type II tumors had the worst language prognosis and longest recovery time. Our classification, which is based on tumor location, can reliably predict postoperative language status and may be used to guide tumor resection.

Left egocentric neglect in early subacute right-stroke patients is related to damage of the superior longitudinal fasciculus

A typical consequence of stroke in the right hemisphere is unilateral spatial neglect. Distinct forms of neglect have been described, such as space-based (egocentric) and object-based (allocentric) neglect. However, the relationship between these two forms of neglect is still far from being understood, as well as their neural substrates. Here, we further explore this issue by using voxel lesion symptoms mapping (VLSM) analyses on a large sample of early subacute right-stroke patients assessed with the Apples Cancellation Test. This is a sensitive test that simultaneously measures both egocentric and allocentric neglect. Behaviourally, we found no correlation between egocentric and allocentric performance, indicating independent mechanisms supporting the two forms of neglect. This was confirmed by the VLSM analysis that pointed out a link between a damage in the superior longitudinal fasciculus and left egocentric neglect. By contrast, no association was found between brain damage and left allocentric neglect. These results indicate a higher probability to observe egocentric neglect as a consequence of white matter damages in the superior longitudinal fasciculus, while allocentric neglect appears more “globally” related to the whole lesion map. Overall, these findings on early subacute right-stroke patients highlight the role played by white matter integrity in sustaining attention-related operations within an egocentric frame of reference.