How to correct susceptibility distortions in spin-echo echo-planar images: application to diffusion tensor imaging

Individual variation in the chimpanzee arcuate fasciculus predicts vocal and gestural communication

Whether language has its evolutionary origins in vocal or gestural communication has long been a matter of debate. In humans, the arcuate fasciculus, a major fronto-temporal white matter tract, is left-lateralized, is larger than in nonhuman apes, and is linked to language. However, the extent to which the arcuate fasciculus of nonhuman apes is linked to vocal and/or manual communication is currently unknown. Here, using probabilistic tractography in 67 chimpanzees (45 female, 22 male), we report that the chimpanzee arcuate fasciculus is not left-lateralized at the population level, in marked contrast with humans. However, individual variation in the anatomy and leftward asymmetry of the chimpanzee arcuate fasciculus is associated with individual variation in the use of both communicative gestures and communicative sounds under volitional orofacial motor control. This indicates that the arcuate fasciculus likely supported both vocal and gestural communication in the chimpanzee/human last common ancestor, 6-7 million years ago.

White-Matter fiber tract and resting-state functional connectivity abnormalities in young children with autism spectrum disorder

Autism spectrum disorder (ASD) is a complex developmental disorder characterized by difficulties in social interaction and communication and repetitive behaviors. Although abnormal brain development has been shown to exist in children with ASD, the link between structural brain abnormalities and resting-state functional connectivity (rsFC) disruptions in children with ASD remains understudied. To address this limitation, we utilized the population-based bundle-to-region connectome, providing a detailed understanding of the connectivity between cortical regions and white matter (WM) tracts. By precisely indexing WM-Gray Matter (GM) interactions, we investigated the rsFC of the cortex-associated ROIs to explore the association between structural and rsFC abnormalities and clinical symptoms in young children with ASD. This MRI study identified significant differences in WM structure and rsFC between children with ASD (n = 34) and typically developing children (TD, n = 43). Our results showed that decreased fractional anisotropy (FA) and increased mean diffusivity (MD) and radial diffusivity (RD) in ASD WM tracts compared to TD, particularly in left hemisphere tracts (anterior thalamic radiation [ATR], cingulum, inferior fronto-occipital fasciculus [IFOF], inferior longitudinal fasciculus [ILF], superior longitudinal fasciculus [SLF], and uncinate fasciculus [UF]). Abnormal rsFC was observed in GM areas connected by ATR, cingulum, IFOF, ILF, and SLF. Furthermore, abnormalities in the structural and functional connectivity index (SFCI) within the SLF and cingulum were identified. An association has been observed between these abnormalities and clinical symptoms. Specifically, SLF structural and functional connectivity appear to be associated with repetitive and restrictive behavior (RRB), while cingulum connectivity is associated with communication abilities. In conclusion, young children with ASD exhibit abnormal WM tract structures and associated rsFC abnormalities. These differences highlight significant disruptions in rsFC mapped from WM tracts to cortical areas in ASD, correlating with the severity of ASD symptoms, and suggest the importance of multi-modal imaging in capturing these variations.

Exploring the causal involvement of the rIPL and white matter interindividual variability in spatial orienting and consciousness

BACKGROUND

Spatial attention enables the selection of relevant over irrelevant stimuli through dorsal and ventral fronto-parietal networks. These networks are connected through long white matter tracts, such as the superior longitudinal fasciculus (SLF) and the Inferior Fronto-Occipital fasciculus (IFOF).

OBJECTIVE/HYPOTHESIS

The main purpose of this study was to explore, in healthy participants, the causal role of the right Inferior Parietal Lobe (rIPL) in spatial orienting and conscious perception. We also explored how interindividual differences in the microstructural properties of white matter were related to the effects of transcranial magnetic stimulation (TMS) and, secondarily, to attentional orienting effects in the control stimulation condition.

METHODS

Participants (n=51) performed a behavioural task involving the detection of a visual stimulus at the threshold of consciousness, preceded by either central (endogenous) or peripheral (exogenous) cues. After cue onset, a burst of TMS pulses was applied over the rIPL or a control active region (vertex). White matter properties were explored through diffusion-weighted imaging tractography and whole-brain NODDI analysis.

RESULTS

TMS over the rIPL (compared to the control condition) did not modulate spatial attention nor conscious perception, but it decreased accuracy when attention was endogenously oriented (compared to the exogenous condition) and speeded up reaction times when targets were presented in the attended right hemifield (compared to the left hemifield). Part of the variability in the TMS and attentional orienting effects were explained by the integrity of the SLF and the IFOF.

CONCLUSIONS

Individual variability in attentional orienting effects was associated with the anatomical links between attentional networks. Negative correlations between TMS effects and relevant white matter tracts were interpreted as compensatory mechanisms, while positive correlations with tracts innervating the stimulated area could reflect a TMS signal propagation effect. These results will contribute to the understanding of the role of white matter variability in the susceptibility to neuromodulation, with potential implications for research and clinical treatment.

Latent preference representation in the human brain for scented products: Effects of novelty and familiarity

Decoding latent preferences for novel products is crucial for understanding decision-making processes, especially when subjective evaluations are unclear. Brain activity in regions like the medial orbitofrontal cortex and nucleus accumbens (NAcc) correlates with subjective preferences. However, whether these regions represent preferences toward novel products and whether coding persists after familiarity remain unclear. We examined the brain coding of latent preferences for novel scented products and how they evolve with familiarity. We measured functional magnetic resonance imaging (fMRI) signals evoked by three fabric softener odors, both when novel and when familiar, in 25 previously unexposed females. To obtain reliable preferences, participants chose one softener after using all three twice at home after the first fMRI measurement (Day 1) and continued using it at home for four months until the second day of the fMRI measurement (Day 2). Subjective ratings were also obtained after each fMRI run. On Day 1, no significant differences in subjective ratings between selected and non-selected odors were found. However, the decoding analysis revealed that future odor preferences for novel products were coded in several regions, including the left superior frontal lobe (SF), right NAcc, and left piriform cortex. On Day 2, the left SF continued to encode preferences after familiarity. These results suggest that odor preferences for novel products are coded in the brain even without conscious awareness, and that the coding in the SF is robust against familiarity. These findings provide insights into a more comprehensive understanding of the brain coding of latent preferences.

Ex vivo brain MRI to assess conventional and FLASH brain irradiation effects

BACKGROUND AND PURPOSE

The FLASH effect expands the therapeutic ratio of tumor control to normal tissue toxicity observed after delivery of ultra-high (>100 Gy/s FLASH-RT) vs. conventional dose rate radiation (CONV-RT). In this first exploratory study, we assessed whether ex vivo Magnetic Resonance Imaging (MRI) could reveal long-term differences after FLASH-RT and CONV-RT whole-brain irradiation.

MATERIALS AND METHODS

Female C57BL/6 mice were divided into three groups: control (non-irradiated), conventional (CONV-RT 0.1 Gy/s), and ultra-high dose rates (FLASH-RT 1 pulse, 5.5 x 10^6 Gy/s), and received 10 Gy of whole-brain irradiation in a single fraction at 10 weeks of age. Mice were evaluated by Novel Object Recognition cognitive testing at 10 months post-irradiation and were sampled at 13 months post-irradiation. Ex vivo brains were imaged with a 14.1 Tesla/26 cm magnet with a multimodal MRI protocol, including T2-weighted TurboRare (T2W) and diffusion-weighted imaging (DWI) sequences.

RESULTS

In accordance with previous results, cognitive tests indicated that animals receiving CONV-RT exhibited a decline in cognitive function, while FLASH-RT performed similarly to the controls. Ex vivo MRI showed decreased hippocampal mean intensity in the CONV-RT mice compared to controls, but not in the FLASH-RT group. Comparing CONV-RT to control, we found significant changes in multiple whole-brain diffusion metrics, including the mean Apparent Diffusion Coefficient (ADC) and Mean Apparent Propagator (MAP) metrics. By contrast, no significant diffusion changes were found between the FLASH-RT and control groups. In an exploratory analysis, compared to controls, regional diffusion metrics were primarily altered in the basal forebrain and the insular cortex after conventional radiation therapy (CONV-RT), and to a lesser extent after flash radiation therapy (FLASH-RT).

CONCLUSION

This study presents initial evidence that ex vivo MRI uncovered changes in the brain after CONV-RT but not after FLASH-RT. The study indicates the potential use of ex vivo MRI to analyze the brain radiation responses at different dose rates.

Dynamic categorization rules alter representations in human visual cortex

Everyday tasks often require stimuli to be categorized dynamically, such that an identical object can elicit different responses based on the current decision rule. Traditionally, sensory regions have been viewed as separate from such context-dependent processing, functioning primarily to process incoming inputs. However, an alternative view suggests sensory regions also integrate inputs with current task goals, facilitating more efficient information relay to higher-level areas. Here we test this by asking human participants to visually categorize novel shape stimuli based on different decision boundaries. Using fMRI and multivariate analyses of retinotopically-defined visual areas, we show that cortical shape representations become more distinct across relevant decision boundaries in a context-dependent manner, with the largest changes in discriminability observed for stimuli near the decision boundary. Importantly, these modulations are associated with improved task performance. These findings demonstrate that visual cortex representations are adaptively modulated to support dynamic behavior.

A multi-site, multi-modal travelling-heads resource for brain MRI harmonisation

Despite its great potential for studying the living brain, magnetic resonance imaging (MRI) can be often limited by nuisance non-biological factors, such as hardware/software differences between scanners, which can interfere with biological variability. This lack of standardisation or harmonisation between scanners hinders reproducibility and quantifiability of MRI. Towards addressing this challenge, we present one of the most comprehensive MRI harmonisation resources, based on a travelling heads paradigm; healthy volunteers scanned repeatedly across different scanners. The Oxford-Nottingham Harmonisation (ON-Harmony) resource offers data from 20 participants each scanned on six different 3 T MRI scanners from three major vendors (GE/Philips/Siemens) across five imaging sites. Each scanning session includes five imaging modalities (T1w/T2w/dMRI/rfMRI/SWI) with protocols aligned to the UK Biobank, while for about half of the participants five within-scanner repeats are additionally acquired. The 165 multi-modal scanning sessions allow mapping of different pools of variability (biological, between-scanner, within-scanner) for hundreds of MRI-derived measures. We describe the breadth of information contained in the publicly-available data and showcase their reuse potential for evaluating efficacy of harmonisation approaches.

Hippocampal microstructural changes following electroconvulsive therapy in severe depression

Electroconvulsive therapy (ECT) induces hippocampal volume increases in depressed patients, potentially reflecting neuroplasticity. We hypothesized that Neurite Orientation Dispersion and Density Imaging (NODDI) could provide in vivo evidence of hippocampal neuroplasticity following ECT. This longitudinal study evaluated 43 depressed patients undergoing ECT and 24 controls. MRI and clinical assessments were performed at baseline (V1), after 5 sessions (V2), and post-treatment (V3). Evaluations included a 3 T MR-scan with 3DT1-weighted and multi-shell diffusion (b = 200/1500/2500 s/mm², 30/45/60directions) sequences. Q-ball, Diffusion Tensor, and NODDI models provided: axial diffusivity (AD), radial diffusivity (RD), mean diffusivity (MD), fractional anisotropy (FA), generalized FA (GFA), neurite density index (NDI), isotropic fraction (Fiso), and orientation dispersion index (ODI). FreeSurfer extracted whole hippocampal and subfield volumes from T1-weighted images. Longitudinal changes were assessed with linear mixed-effect models. 107 MRIs from patients and 24 MRIs from controls were analyzed. ECT induced significant bilateral hippocampal volume increases (p < 0.001). Group comparisons showed consistently higher FA, lower GFA and ODI in patients compared to controls at all time-points. Following ECT, significant diffusion changes included decreased hippocampal GFA, FA, AD, MD and Fiso, along with increased ODI and NDI. NDI and Fiso changes were localized to the dentate gyrus but not the hippocampal tail. ECT responders showed a significant right hippocampal volume increase at V2 compared to non-responders. After ECT, hippocampal volume increases are accompanied by bilateral changes in NODDI parameters, particularly in the dentate gyrus, consistent with hippocampal neuroplasticity.

Radiomic Profiling of Orthotopic Mouse Models of Glioblastoma Reveals Histopathological Correlations Associated with Tumour Response to Ionising Radiation

BACKGROUND

Glioblastoma (GB) is a particularly malignant brain tumour which carries a poor prognosis and presents limited treatment options. MRI is standard practice for differential diagnosis at initial presentation of GB and can assist in both treatment planning and response assessment. MRI radiomics allows for discerning GB features of clinical importance that are not evident by visual analysis, augmenting the morphological and functional tumour characterisation beyond traditional imaging techniques. Given that radiotherapy is part of the standard of care for GB patients, establishing a platform for phenotyping radiation treatment responses using non-invasive methods is of high relevance.

METHODS

In this study, we modelled the responses to ionising radiation across four orthotopic mouse models of GB using diffusion and perfusion radiomics. We have identified the optimal set of radiomic features that reflect tumour cellularity, microvascularity, and blood flow changes brought about by radiation treatment in these murine orthotopic models of GB, and directly compared them with endpoint histopathological analysis.

RESULTS

We showed that the selected radiomic features can quantify textural information and pixel interrelationships of tumour response to radiation therapy, revealing subtle image patterns that may reflect intra-tumoural spatial heterogeneity. When compared to GB patients, similarities in selected radiomic features were noted between orthotopic murine tumours and non-enhancing central tumour areas in patients, along with several discrepancies in tumour cellularity and vascularization, denoted by distinct grey level intensities and nonuniformity metrics.

CONCLUSION

As the field evolves, radiomic profiling of GB may enhance the evaluation of targeted therapeutic strategies, accelerate the development of new therapies, and act as a potential virtual biopsy tool.

Longitudinal trajectories of brain development from infancy to school age and their relationship to literacy development

Reading is one of the most complex skills that we utilize daily, and it involves the early development and interaction of various lower-level subskills, including phonological processing and oral language. These subskills recruit brain structures, which begin to develop long before the skill manifests and exhibit rapid development during infancy. However, how longitudinal trajectories of early brain development in these structures support long-term acquisition of literacy subskills and subsequent reading is unclear. Children underwent structural and diffusion MRI scanning at multiple timepoints between infancy and second grade and were tested for literacy subskills in preschool and decoding and word reading in early elementary school. We developed and implemented a reproducible pipeline to generate longitudinal trajectories of early brain development to examine associations between these trajectories and literacy (sub)skills. Furthermore, we examined whether familial risk of reading difficulty and children's home literacy environments, two common literacy-related covariates, influenced those trajectories. Results showed that individual differences in curve features (e.g., intercepts and slopes) for longitudinal trajectories of volumetric, surface-based, and white matter organization measures were linked directly to phonological processing and indirectly to first-grade decoding and word reading skills via phonological processing. Altogether, these findings suggest that the brain bases of phonological processing, previously identified as the strongest behavioral predictor of reading and decoding skills, may already begin to develop by birth but undergo further refinement between infancy and preschool. The present study underscores the importance of considering academic skill acquisition from the very beginning of life.

Fibre density and cross-section associate with hallmark pathology in early Alzheimer's disease

BACKGROUND

Tau pathology in Alzheimer's disease (AD) propagates trans-synaptically along structurally connected brain networks and in synergy with amyloid pathology it induces synaptic damage. However, the in vivo relationship of amyloid, tau and synaptic density with white matter (WM) structural changes has been studied rather limitedly. Recent advances in diffusion MRI processing allow quantification of apparent fibre density and fibre cross-section on the fixel level, i.e., individual fibre populations within one voxel. The aim of this study was to investigate the hypothesis of axonal loss due to tau propagation and amyloid pathology and its association with synaptic density in early disease stages.

METHODS

Twenty-four patients with amnestic mild cognitive impairment (aMCI) and 23 healthy controls (HC) underwent baseline amyloid (11C-PiB/18F-NAV4694), tau (18F-MK-6240) and synaptic density (11C-UCB-J binding to SV2A) PET/MR in combination with diffusion MRI and cognitive assessments. A subset of 14 aMCI patients underwent follow-up visits after 2 years. First, a whole-brain fixel-based analysis was performed to identify differences in fibre density and fibre cross-section between HC and aMCI and longitudinally in the aMCI group. Next, a tract-of-interest analysis was performed, focusing on the temporal-cingulum bundle where most alterations have been shown in early AD. Tau and SV2A PET were quantified in the connected regions, i.e., hippocampus and posterior cingulate/precuneus (PCC-P). Amyloid PET centiloids were measured in the commonly used cortical composite volume-of-interest.

RESULTS

At baseline, multiple WM tracts showed lower fibre density and lower fibre cross-section in aMCI compared to HC, and these parameters further decreased longitudinally in the aMCI group. In the temporal cingulum bundle, reduced fibre density was significantly associated with reduced hippocampal synaptic density while increased hippocampal and PCC-P tau specifically correlated with reduced fibre cross-section. Increased global amyloid burden was associated with reduced fibre density and fibre cross-section in the temporal cingulum bundle.

CONCLUSIONS

Our results suggest that WM degeneration already occurs in the aMCI stage of AD and alterations in apparent fibre density and fibre cross-section of the temporal cingulum bundle are associated with AD hallmark pathology.

Neurocognitive mechanisms underlying action tool knowledge tasks: specificity of tool-tool compared to hand-tool compatibility tasks

Action tool knowledge can be assessed mainly with two kinds of tasks: tool-tool and hand-tool compatibility tasks. While these tasks are used to assess action tool knowledge, recent data showed striking dissociations between these tasks in brain-damaged patients. In this study, we explored the neuropsychological dissociations (Experiment 1; 60 brain-damaged patients) and the potential cognitive mechanisms engaged during these two tasks (Experiment 2; 52 healthy participants). Finally, we also reanalyzed fMRI data to investigate the neural bases engaged in tool-tool and hand-tool compatibility tasks (Experiment 3; 34 healthy participants). The three experiments provide convergent arguments by showing that both tasks share common core computations supported by a left-lateralized brain network, but hand-tool compatibility task engages regions outside of this brain network and is explained by visual imagery while tool-tool task is rather explained by motor imagery. Our results shed a new light on action tool knowledge tasks.

New physiological insights using multi-TE ASL MRI measuring blood-brain barrier water exchange after caffeine intake

OBJECTIVES

Caffeine, a known neurostimulant and adenosine antagonist, affects brain physiology by decreasing cerebral blood flow. It interacts with adenosine receptors to induce vasoconstriction, potentially disrupting brain homeostasis. However, the impact of caffeine on blood-brain barrier (BBB) permeability to water remains underexplored. This study investigated the water exchange via the BBB in a perturbed physiological condition caused by caffeine ingestion, using the multiple echo time (multi-TE) arterial spin labeling (ASL) technique.

MATERIAL AND METHODS

Ten healthy, regular coffee drinkers (age = 31 ± 9 years, 3 females) were scanned to acquire five measurements before and six measurements after caffeine ingestion. Data were analyzed with a multi-TE two-compartment model to estimate exchange time (Tex), serving as a proxy for BBB permeability to water. Additionally, cerebral blood flow (CBF), arterial transit time (ATT), and intravoxel transit time (ITT) were investigated.

RESULTS

Following caffeine intake, mean gray matter CBF showed a significant time-dependent decrease (P < 0.01). In contrast, Tex, ATT, and ITT did not exhibit significant time-dependent change. However, a non-significant decreasing trend was observed for Tex and ITT, respectively, while ATT showed an increasing trend over time.

DISCUSSION

The observed decreasing trend in Tex after caffeine ingestion suggests a potential increase in water flux across the BBB, which may represent a compensatory mechanism to maintain brain homeostasis in response to the caffeine-induced reduction in CBF. Further studies with larger sample sizes are needed to validate and expand upon these findings.

Network segregation during episodic memory shows age-invariant relations with memory performance from 7 to 82 years

Lower episodic memory capability, as seen in development and aging compared with younger adulthood, may partly depend on lower brain network segregation. Here, our objective was twofold: (1) test this hypothesis using within- and between-network functional connectivity (FC) during episodic memory encoding and retrieval, in two independent samples (n = 734, age 7-82 years). (2) Assess associations with age and the ability to predict memory comparing task-general FC and memory-modulated FC. In a multiverse-inspired approach, we performed tests across multiple analytic choices. Results showed that relationships differed based on these analytic choices and were mainly present in the largest dataset,. Significant relationships indicated that (i) memory-modulated FC predicted memory performance and associated with memory in an age-invariant manner. (ii) In line with the so-called neural dedifferentiation view, task-general FC showed lower segregation with higher age in adults which was associated with worse memory performance. In development, although there were only weak signs of a neural differentiation, that is, gradually higher segregation with higher age, we observed similar lower segregation-worse memory relationships. This age-invariant relationships between FC and episodic memory suggest that network segregation is pivotal for memory across the healthy lifespan.

Moral conviction interacts with metacognitive ability in modulating neural activity during sociopolitical decision-making

The extent to which a belief is rooted in one's sense of morality has significant societal implications. While moral conviction can inspire positive collective action, it can also prompt dogmatism, intolerance, and societal divisions. Research in social psychology has documented the functional characteristics of moral conviction and shows that poor metacognition exacerbates its negative outcomes. However, the cognitive and neural mechanisms underlying moral conviction, their relationship with metacognition, and how moral conviction is integrated into the valuation and decision-making process remain unclear. This study investigated these neurocognitive processes during decision-making on sociopolitical issues varying in moral conviction. Participants (N = 44) underwent fMRI scanning while deciding, on each trial, which of two groups of political protesters they supported more. As predicted, stronger moral conviction was associated with faster decision times. Hemodynamic responses in the anterior insula (aINS), anterior cingulate cortex (ACC), and lateral prefrontal cortex (lPFC) were elevated during decisions with higher moral conviction, supporting the emotional and cognitive dimensions of moral conviction. Functional connectivity between lPFC and vmPFC was greater on trials higher in moral conviction, elucidating mechanisms through which moral conviction is incorporated into valuation. Average support for the two displayed groups of protesters was positively associated with brain activity in regions involved in valuation, particularly vmPFC and amygdala. Metacognitive sensitivity, the ability to discriminate one's correct from incorrect judgments, measured in a perceptual task, negatively correlated with parametric effects of moral conviction in the brain, providing new evidence that metacognition modulates responses to morally convicted issues.

Brainwide mesoscale functional networks revealed by focal infrared neural stimulation of the amygdala

The primate amygdala serves to evaluate the emotional content of sensory inputs and modulate emotional and social behaviors; it modulates cognitive, multisensory and autonomic circuits predominantly via the basal, lateral and central nuclei, respectively. Recent evidence has suggested the mesoscale (millimeter-scale) nature of intra-amygdala functional organization. However, the connectivity patterns by which these mesoscale regions interact with brainwide networks remain unclear. Using infrared neural stimulation of single mesoscale sites coupled with mapping in ultrahigh field 7-T functional magnetic resonance imaging, we have discovered that these mesoscale sites exert influence over a surprisingly extensive scope of the brain. Our findings strongly indicate that mesoscale sites within the amygdala modulate brainwide networks through a 'one-to-many' (integral) way. Meanwhile, these connections exhibit a point-to-point (focal) topography. Our work provides new insights into the functional architecture underlying emotional and social behavioral networks, thereby opening up possibilities for individualized modulation of psychological disorders.

Romer-EPTI: Rotating-view motion-robust super-resolution EPTI for SNR-efficient distortion-free in-vivo mesoscale diffusion MRI and microstructure imaging

PURPOSE

To overcome the major challenges in diffusion MRI (dMRI) acquisition, including limited SNR, distortion/blurring, and susceptibility to motion artifacts.

THEORY AND METHODS

A novel Romer-EPTI technique is developed to achieve SNR-efficient acquisition while providing distortion-free imaging, minimal spatial blurring, high motion robustness, and simultaneous multi-TE imaging. It introduces a ROtating-view Motion-robust supEr-Resolution technique (Romer) combined with a distortion/blurring-free Echo Planar Time-resolved Imaging (EPTI) readout. Romer enhances SNR through simultaneous multi-thick-slice acquisition with rotating-view encoding, while providing high motion-robustness via a high-fidelity, motion-aware super-resolution reconstruction. Instead of EPI, the in-plane encoding is performed using EPTI readout to prevent geometric distortion, T2/T2*-blurring, and importantly, dynamic distortions that could introduce additional blurring/artifacts after super-resolution reconstruction due to combining volumes with inconsistent geometries. This further improves effective spatial resolution and motion robustness. Additional developments include strategies to address slab-boundary artifacts, achieve minimized TE and optimized readout for additional SNR gain, and increase robustness to strong phase variations at high b-values.

RESULTS

Using Romer-EPTI, we demonstrated distortion-free whole-brain mesoscale in-vivo dMRI at both 3T (500-μm isotropic [iso] resolution) and 7T (485-μm iso resolution) for the first time. Motion experiments demonstrated the technique's motion robustness and its ability to obtain high-resolution diffusion images in the presence of subject motion. Romer-EPTI also demonstrated high SNR gain and robustness in high b-value (b = 5000 s/mm2) and time-dependent dMRI.

CONCLUSION

The high SNR efficiency, improved image quality, and motion robustness of Romer-EPTI make it a highly efficient acquisition for high-resolution dMRI and microstructure imaging.

Cognitive traits shape the brain activity associated with mental rotation

Mental rotation is a spatial cognitive ability influenced by several factors, including cognitive traits. However, the relationship between mental rotation performance, cognitive traits, and brain activity is still uncertain. To fill this gap, we recorded functional magnetic resonance imaging data while 55 neurotypical participants performed mental rotation with images of geometric objects, human bodies, and real objects. Cognitive traits were evaluated through the Object-Spatial Imagery Questionnaire (visual cognitive style), a perspective-taking task, and the Cognitive Flexibility Scale. Analysis of accuracy and reaction time revealed that (i) mental rotation in spatial-visualizers was more accurate and faster than in object-visualizers, and (ii) visual cognitive style and perspective-taking positively correlated with mental rotation. Brain activity data indicated that (i) individuals with better mental rotation performance had smaller brain activation, particularly in sensorimotor regions, (ii) for the spatial-visual scale and perspective-taking, high scorers had smaller brain activity than low performers, (iii) for the object-visual scale, high scorers had greater brain activity than low scorers. Supporting a neural efficiency hypothesis, the present study highlights the influence of cognitive traits on mental rotation performance and brain efficiency, with spatial-visualizers showing more efficient neural processing. These findings contribute to our understanding of how cognitive styles shape spatial cognition.

Comparison of Echo Planar and Turbo Spin Echo Diffusion-Weighted Imaging in Intraoperative MRI

BACKGROUND

Diffusion-weighted imaging (DWI) is routinely used in brain tumor surgery guided by intraoperative MRI (IoMRI). However, conventional echo planar imaging DWI (EPI-DWI) is susceptible to distortion and artifacts that affect image quality. Turbo spin echo DWI (TSE-DWI) is an alternative technique with minimal spatial distortions that has the potential to be the radiologically preferred sequence.

PURPOSE

To compare via single- and multisequence assessment EPI-DWI and TSE-DWI in the IoMRI setting to determine whether there is a radiological preference for either sequence.

STUDY TYPE

Retrospective.

POPULATION

Thirty-four patients (22 female) aged 2-61 years (24 under 18 years) undergoing IoMRI during surgical resection of intracranial tumors.

FIELD STRENGTH/SEQUENCE

3-T, EPI-DWI, and TSE-DWI.

ASSESSMENT

Patients were scanned with EPI- and TSE-DWI as part of the standard IoMRI scanning protocol. A single-sequence assessment of spatial distortion and image artifact was performed by three neuroradiologists blinded to the sequence type. Images were scored regarding distortion and artifacts, around and remote to the resection cavity. A multisequence radiological assessment was performed by three neuroradiologists in full radiological context including all other IoMRI sequences from each case. The DWI images were directly compared with scorings of the radiologists on which they preferred with respect to anatomy, abnormality, artifact, and overall preference.

STATISTICAL TESTS

Wilcoxon signed-rank tests for single-sequence assessment, weighted kappa for single and multisequence assessment. A P-value <0.001 was considered statistically significant.

RESULTS

For the blinded single-sequence assessment, the TSE-DWI sequence was scored equal to or superior to the EPI-DWI sequence for distortion and artifacts, around and remote to the resection cavity for every case. In the multisequence assessment, all radiologists independently expressed a preference for TSE-DWI over EPI-DWI sequences on viewing brain anatomy, abnormalities, and artifacts.

DATA CONCLUSION

The TSE-DWI sequences may be favored over EPI-DWI for IoMRI in patients with intracranial tumors.

LEVEL OF EVIDENCE

2 TECHNICAL EFFICACY: Stage 5.

Functional and vascular neuroimaging in maritime pilots with long-term sleep disruption

The mechanism underlying the possible causal association between long-term sleep disruption and Alzheimer's disease remains unclear Musiek et al. 2015. A hypothesised pathway through increased brain amyloid load was not confirmed in previous work in our cohort of maritime pilots with long-term work-related sleep disruption Thomas et al. Alzheimer's Res Ther 2020;12:101. Here, using functional MRI, T2-FLAIR, and arterial spin labeling MRI scans, we explored alternative neuroimaging biomarkers related to both sleep disruption and AD: resting-state network co-activation and between-network connectivity of the default mode network (DMN), salience network (SAL) and frontoparietal network (FPN), vascular damage and cerebral blood flow (CBF). We acquired data of 16 maritime pilots (56 ± 2.3 years old) with work-related long-term sleep disruption (23 ± 4.8 working years) and 16 healthy controls (59 ± 3.3 years old), with normal sleep patterns (Pittsburgh Sleep Quality Index ≤ 5). Maritime pilots did not show altered co-activation in either the DMN, FPN, or SAL and no differences in between-network connectivity. We did not detect increased markers of vascular damage in maritime pilots, and additionally, maritime pilots did not show altered CBF-patterns compared to healthy controls. In summary, maritime pilots with long-term sleep disruption did not show neuroimaging markers indicative of preclinical AD compared to healthy controls. These findings do not resemble those of short-term sleep deprivation studies. This could be due to resiliency to sleep disruption or selection bias, as participants have already been exposed to and were able to deal with sleep disruption for multiple years, or to compensatory mechanisms Mentink et al. PLoS ONE. 2021;15(12):e0237622. This suggests the relationship between sleep disruption and AD is not as strong as previously implied in studies on short-term sleep deprivation, which would be beneficial for all shift workers suffering from work-related sleep disruptions.

Evaluation of the glymphatic system in relapsing remitting multiple sclerosis by measuring the diffusion along the perivascular space

BACKGROUND

In the inflammatory process of multiple sclerosis (MS) several toxic waste products are generated. The clearance of these products might depend on the glymphatic system; however, it's preserved function in MS is uncertain. Recently, it was suggested that this 'waste clearance' system can be examined by measuring the diffusion along the perivascular space (ALPS) index.

METHODS

Reproducibility of the ALPS index was tested with intraclass correlation on two open-source datasets with two methods: calculating ALPS indices from the skeleton map (sk-ALPS) and via registration to the common space (ro-ALPS). ALPS indices of 66 MS patient were calculated via the reorientation method. Spearman's correlation and partial least squares regression were applied to reveal the connection between the ALPS indices and the radiological (lesion count) and clinical parameters (SDMT, BVMT, CVLT, EDSS, disease duration) of the patients.

RESULTS

Repeatability of the ALPS index calculated by the ro-ALPS method is the most reliable (ICC: 0.961). Significant correlation was found between the left ALPS index and SDMT. On the right side, significant correlation was found between the ALPS index and the number of periventricular lesions and black holes. The most important predictors of EDSS are disease duration, age, SDMT and infratentorial lesion count.

CONCLUSION

Reproducibility of the ALPS index ranges from 'good' to 'excellent'. No relationship was found between the ALPS index and clinical disability. A lateralization was observed with cognitive characteristics on the left sided ALPS index and radiological characteristics on the right sided ALPS index.

Microstructural abnormalities of the dentato-rubro-thalamo-cortical tract in tremor dominant Parkinson's disease and essential tremor plus syndrome

PURPOSE

The dentato-rubro-thalamo-cortical tract (DRTC) is considered to play a crucial role across tremor disorders including tremor dominant Parkinson's disease (TDPD) and essential tremor plus (ETP). This study aims to comprehensively evaluate microstructural integrity of the DRTC using single-compartment, i.e., DTI, and multi-compartment, i.e., neurite orientation dispersion and distribution imaging (NODDI), and free water (FW) based analysis.

METHODS

DTI, NODDI and FW based metrics were estimated for 25 TDPD, 25 ETP (Essential tremor with rest tremor) and 22 healthy controls (HC). TBSS was carried out followed by voxelwise statistics on respective metric skeletons with TFCE correction and custom FA skeleton masks for left and right DRTC tracts. Masks generated from significant clusters, and whole tract masks were utilised in quantitative analysis. ROI based subject space analysis was also carried out for whole tract and TBSS cluster values. Quantitative analysis was carried out using MANCOVA with age and gender as covariates. Clinical features between TDPD and ETP were compared using t-test.

RESULTS

There was no difference in the Fahn-Tolosa-Marin tremor rating scale score. Compared to HC, TDPD showed lower neurite density index, higher axial diffusivity (AD), mean diffusivity (MD), FW corrected MD in the thalamo-cortical section of the left DRTC. No statistically significant differences were observed between ETP and HC or TDPD and ETP.

CONCLUSIONS

TDPD demonstrated asymmetric reduction in neurite density and increased MD, fwMD and AD in the thalamo-cortical section of DRTC. The absence of differences between ETP and TDPD may suggest the possibility of similarities in tremor pathogenesis.

Pre-choice midbrain fluctuations affect self-control in food choice: A functional magnetic resonance imaging (fMRI) study

Recent studies have shown that spontaneous pre-stimulus fluctuations in brain activity affect higher-order cognitive processes, including risky decision-making, cognitive flexibility, and aesthetic judgments. However, there is currently no direct evidence to suggest that pre-choice activity influences value-based decisions that require self-control. We examined the impact of fluctuations in pre-choice activity in key regions of the reward system on self-control in food choice. In the functional magnetic resonance imaging (fMRI) scanner, 49 participants made 120 food choices that required self-control in high and low working memory load conditions. The task was designed to ensure that participants were cognitively engaged and not thinking about upcoming choices. We defined self-control success as choosing a food item that was healthier over one that was tastier. The brain regions of interest (ROIs) were the ventral tegmental area (VTA), putamen, nucleus accumbens (NAc), and caudate nucleus. For each participant and condition, we calculated the mean activity in the 3-s interval preceding the presentation of food stimuli in successful and failed self-control trials. These activities were then used as predictors of self-control success in a fixed-effects logistic regression model. The results indicate that increased pre-choice VTA activity was linked to a higher probability of self-control success in a subsequent food-choice task within the low-load condition, but not in the high-load condition. We posit that pre-choice fluctuations in VTA activity change the reference point for immediate (taste) reward evaluation, which may explain our finding. This suggests that the neural context of decisions may be a key factor influencing human behavior.

The Bulb, the Brain and the Being: New Insights into Olfactory System Anatomy, Organization and Connectivity

BACKGROUND/OBJECTIVES

Olfaction is in many ways the least understood sensory modality. Its organization and connectivity are still under debate. The aim of this study was to investigate the anatomy of the olfactory system by using a cadaver fiber dissection technique and in vivo tractography to attain a deeper understanding of the subcortical connectivity and organization.

METHODS

Ten cerebral hemispheres were used in this study for white matter dissection according to Klingler's technique. Measurements of different cortical structures and interhemispheric symmetry were compared. Diffusion tensor imaging sequences from twenty-five healthy individuals from the Human Connectome Project dataset were used to explore the connectivity of the olfactory system using DSI Studio. White matter connectivity between the following were reconstructed in vivo: (1) Olfactory bulb to primary olfactory cortices; (2) Olfactory bulb to secondary olfactory cortices; (3) Primary to secondary olfactory cortices. The DTI metrics of the identified major associative, projection and commissural pathways were subsequently correlated with olfactory function and cognition in seventy-five healthy individuals with Spearman's rank correlation and the Benjamini-Hochberg method for false discoveries (CI 95%, p < 0.05) using R.

RESULTS

1. The dissection showed that the lateral stria was significantly longer on the left side and projected towards the amygdala, the entorhinal and piriform cortex. 2. The medial stria was not evident as a consistent white matter structure. 3. Both dissection and tractography showed that major associative white matter pathways such as the uncinate fasciculus, the inferior fronto-occipital fasciculus and cingulum supported the connectivity between olfactory areas together with the anterior commissure. 4. No significant correlation was found between DTI metrics and sensory or cognition test results.

CONCLUSIONS

We present the first combined fiber dissection analysis and tractography of the olfactory system. We propose a novel definition where the primary olfactory network is defined by the olfactory tract/bulb and primary olfactory cortices through the lateral stria only. The uncinate fasciculus, inferior fronto-occipital fasciculus and cingulum are the associative pathways supporting the connectivity between primary and secondary olfactory areas together with the anterior commissure. We suggest considering these structures as a secondary olfactory network. Further work is needed to attain a deeper understanding of the pathological and physiological implications of the olfactory system.

Multimodal precision MRI of the individual human brain at ultra-high fields

Multimodal neuroimaging, in particular magnetic resonance imaging (MRI), allows for non-invasive examination of human brain structure and function across multiple scales. Precision neuroimaging builds upon this foundation, enabling the mapping of brain structure, function, and connectivity patterns with high fidelity in single individuals. Highfield MRI, operating at magnetic field strengths of 7 Tesla (T) or higher, increases signal-to-noise ratio and opens up possibilities for gains spatial resolution. Here, we share a multimodal Precision Neuroimaging and Connectomics (PNI) 7 T MRI dataset. Ten healthy individuals underwent a comprehensive MRI protocol, including T1 relaxometry, magnetization transfer imaging, T2*-weighted imaging, diffusion MRI, and multi-state functional MRI paradigms, aggregated across three imaging sessions. Alongside anonymized raw MRI data, we release cortex-wide connectomes from different modalities across multiple parcellation scales, and supply "gradients" that compactly characterize spatial patterning of cortical organization. Our precision MRI dataset will advance our understanding of structure-function relationships in the individual human brain and is publicly available via the Open Science Framework.

Diffusion MRI GAN synthesizing fibre orientation distribution data using generative adversarial networks

Machine learning may enhance clinical data analysis but requires large amounts of training data, which are scarce for rare pathologies. While generative neural network models can create realistic synthetic data such as 3D MRI volumes and, thus, augment training datasets, the generation of complex data remains challenging. Fibre orientation distributions (FODs) represent one such complex data type, modelling diffusion as spherical harmonics with stored weights as multiple three-dimensional volumes. We successfully trained an α-WGAN combining a generative adversarial network and a variational autoencoder to generate synthetic FODs, using the Human Connectome Project (HCP) data. Our resulting synthetic FODs produce anatomically accurate fibre bundles and connectomes, with properties matching those from our validation dataset. Our approach extends beyond FODs and could be adapted for generating various types of complex medical imaging data, particularly valuable for augmenting limited clinical datasets.

The Growing Little Brain: Cerebellar Functional Development from Cradle to School

Despite the cerebellum's crucial role in brain functions, its early development, particularly in relation to the cerebrum, remains poorly understood. Here, we examine cerebellocortical connectivity using over 1,000 high-quality resting-state functional MRI scans of children from birth to 60 months. By mapping cerebellar topography with fine temporal detail for the first time, we show the hierarchical organization of cerebellocortical functional connectivity from infancy. We observe dynamic shifts in cerebellar network gradients, which become more focal with age while generally maintaining stable anchor points similar to adults, highlighting the cerebellum's evolving yet stable role in functional integration during early development. Our findings provide the first evidence of cerebellar connections to higher-order networks at birth, which generally strengthen with age, emphasizing the cerebellum's early role in cognitive processing beyond sensory and motor functions. Our study provides insights into early cerebellocortical interactions, reveals functional asymmetry and sex-specific patterns in cerebellar development, and lays the groundwork for future research on cerebellum-related disorders in children.

Hemifield Specificity of Attention Response Functions During Multiple Object Tracking

The difficulty of tracking multiple moving objects among identical distractors increases with the number of tracked targets. Previous research has shown that the number of targets tracked (i.e., load) modulates activity in brain areas related to visuospatial attention, giving rise to so-called "Attention Response Functions" (ARFs). While the hemifield/hemispheric effects of spatial attention (e.g., hemispatial neglect, hemifield capacity limits) are well described, it had not previously been tested whether a hemispheric or hemifield imbalance exists among ARFs. By recording BOLD activity from human brains (n=19, female and male) in a multiple object tracking paradigm, we show that the number of tracked objects modulates activity in a large network of areas bilaterally. A significant effect of contralateral load was found in earlier areas throughout the dorsal and ventral visual streams, while the effects of ipsilateral load emerged in later areas. Both contra- and ipsilateral load significantly influenced activity in the parietal and frontal lobes, specifically the dorsal attention network. In addition, some brain regions in the occipital lobe were significantly more sensitive to contralateral than ipsilateral load. Our results are consistent with findings showing that a diverse set of brain areas contributes to tracking multiple targets. In particular, we extend the canonical view of load-based ARFs to include hemifield bias. Given the hemifield-specific nature of speed and capacity limits to multiple object tracking, we conjecture that areas that show a strong hemifield preference may impose a bottleneck on processing that results in limits on the capacity and speed of tracking.Significance Statement We investigated how attentional effort impacts brain activity. Effort (the number of targets in a multiple object tracking task) parametrically drives activity in the attention system. Our findings reveal brain areas where effort driven increases in activity are dependent on the visual hemifield where targets are tracked. We show that the load-dependent responses differ between earlier visual areas, which prefer targets on the contralateral side, and later areas that respond to targets anywhere in the visual field. This research challenges previous explanations of hemispatial neglect and enhances our understanding of how the brain manages spatial attention and mental effort. Additionally, we identify regions that might be the source of hemifield-specific capacity limits in attentional tracking.

White-Matter Connectivity and General Movements in Infants with Perinatal Brain Injury

BACKGROUND/OBJECTIVES

Cerebral palsy (CP), often caused by early brain injury such as perinatal stroke or hemorrhage, is the most common lifelong motor disability. Early identification of at-risk infants and timely access to rehabilitation interventions are essential for improving long-term outcomes. The General Movements Assessment (GMA), performed in the first months of life, has high sensitivity and specificity to predict CP; however, the neurological correlates of general movements remain unclear. This analysis aimed to investigate the relationship between white matter integrity and general movements in infants with perinatal brain injury using advanced neuroimaging techniques.

METHODS

Diffusion-weighted MRI data were analyzed in 17 infants, 12 with perinatal brain injury and 5 typically developing infants. Tractography was used to identify the corticospinal tract, a key motor pathway often affected by perinatal brain injury, and tract-based spatial statistics (TBSS) were used to examine broader white matter networks. Diffusion parameters from the diffusion tensor imaging (DTI) and neurite orientation dispersion and density imaging (NODDI) models were compared between infants with and without typical general movements.

RESULTS

Corticospinal tract integrity did not differ between groups when averaged across hemispheres. However, infants with asymmetric general movements exhibited greater corticospinal tract asymmetries. A subset of infants with atypical general movement trajectories at <6 weeks and 3-5 months of age showed reduced corticospinal tract integrity compared to those with typical general movements. TBSS revealed significant differences in white matter integrity between infants with typical and atypical general movements in several white matter pathways, including the corpus callosum, the right posterior corona radiata, bilateral posterior thalamic radiations, the left fornix/stria terminalis, and bilateral tapetum.

CONCLUSIONS

These findings support and expand upon previous research suggesting that white matter integrity across multiple brain regions plays a role in the formation of general movements. Corticospinal integrity alone was not strongly associated with general movements; interhemispheric and cortical-subcortical connectivity appear critical. These findings underscore the need for further research in larger, diverse populations to refine early biomarkers of neurodevelopmental impairment and guide targeted interventions.

Longitudinal changes in brain connectivity correlate with neuropsychological testing in brain tumor resection patients

Background

Patients undergoing brain tumor resection experience neurological and cognitive (i.e., neurocognitive) changes reflected in altered performance on neuropsychological tests. These changes can be difficult to explain or predict. Brain connectivity, measured with neuroimaging, offers one potential model for examining these changes. In this study, we evaluated whether longitudinal changes in brain connectivity correlated with changes in neurocognitive abilities in patients before and after brain tumor resection.

Methods

Patients underwent functional and diffusion MR scanning and neuropsychological evaluation before tumor resection followed by repeat scanning and evaluation 2 weeks post-resection. Using this functional and diffusion imaging data, we measured changes in the topology of the functional and structural networks. From the neuropsychological testing scores, we derived a composite score that described a patient's overall level of neurocognitive functioning. We then used a multiple linear regression model to test whether structural and functional connectivity measures were correlated with changes in composite scores.

Results

Multiple linear regression on 21 subjects showed that functional connectivity changes were highly correlated with changes in neuropsychological evaluation scores (R2 adjusted = 0.79, p < 0.001). Changes in functional local efficiency (p < 0.001) and global efficiency (p < 0.05) were inversely correlated with changes in composite score, while changes in modularity (p < 0.01) as well as the patient's age (p < 0.05) were directly correlated with changes in composite score.

Conclusion

Short interval changes in brain functional connectivity markers were strongly correlated with changes in the composite neuropsychological test scores in brain tumor resection patients. Our findings support the need for further exploration of brain connectivity as a biomarker relevant to brain tumor patients.

Anatomically distinct regions in the inferior frontal cortex are modulated by task and reading skill

Inferior frontal cortex (IFC) is a critical region for reading and language. This part of the cortex is highly heterogeneous in its structural and functional organization and shows high variability across individuals. Despite decades of research, the relationship between specific IFC regions and reading skill remains unclear. To shed light on the function of IFC in reading, we aim to (1) characterize the functional landscape of text-selective responses in IFC, while accounting for interindividual variability; and (2) examine how text-selective regions in the IFC relate to reading proficiency. To this end, children with a wide range of reading ability (N=66; age 7-14 years, 34 female, 32 male) completed functional MRI scans while performing two tasks on text and non-text visual stimuli. Importantly, both tasks do not explicitly require reading, and can be performed on all visual stimuli. This design allows us to tease apart stimulus-driven responses from task-driven responses and examine where in IFC task and stimulus interact. We were able to identify three anatomically-distinct, text-selective clusters of activation in IFC, in the inferior frontal sulcus (IFS), and dorsal and ventral precentral gyrus (PrG). ​​These three regions showed a strong task effect that was highly specific to text. Furthermore, text-selectivity in the IFS and dorsal PrG was associated with reading proficiency, such that better readers showed higher selectivity to text. These findings suggest that text-selective regions in the IFC are sensitive to both stimulus and task, and highlight the importance of this region for proficient reading.Significance statement The inferior frontal cortex (IFC) is a critical region for language processing, yet despite decades of research, its relationship with reading skill remains unclear. In a group of children with a wide range of reading skills, we were able to identify three anatomically distinct text-selective clusters of activation in the IFC. ​​These regions showed a strong task effect that was highly selective to text. Text-selectivity was positively correlated with reading proficiency, such that better readers showed higher selectivity to text, even in tasks that did not require reading. These findings suggest that multiple text-selective regions within IFC are sensitive to both stimulus and task, and highlight the critical role of IFC for reading proficiency.

Large-Scale High-Resolution Probabilistic Maps of the Human Superior Longitudinal Fasciculus Subdivisions and their Cortical Terminations

The superior longitudinal fasciculus (SLF) is the large white matter association tract connecting the prefrontal and posterior parietal cortices. Past studies in non-human primates have parcellated the SLF into three subdivisions and have outlined the specific cortico-cortical organization and terminations for each subdivision. However, it is difficult to characterize these structural connections in humans to the specificity of tract-tracing studies in animals. This has led to disagreement on how the SLF subdivisions are organized in the human brain, including if the dorsomedial SLF (SLF-I) is part of the cingulum subsystem. Here, we present a novel large-scale, probabilistic map of the SLF subdivisions, using high-resolution diffusion imaging data from the Human Connectome Project (HCP). We used image data from 302 adult males and 405 adult females to model the three SLF subdivisions in each hemisphere, and attempted to characterize the frontal and parietal termination points for each subdivision. SLF subdivisions were successfully modeled in each subject, showing the dorsomedial-to-ventrolateral organization similar to that in nonhuman primate histological studies. We also found minimal differences between SLF-I models with and without the cingulate gyrus excluded, suggesting that the SLF-I may be a separable tract from the cingulum. Lastly, the SLF subdivisions showed differentiable associations with major cognitive domains such as memory and executive functions. While histological confirmation is needed beyond tractography, these probabilistic masks offer a first step in guiding future exploration of frontoparietal organization by providing detailed characterization of the SLF subdivisions and their potential cortical terminations.Significance statement The prefrontal and posterior parietal areas are interconnected via the SLF, which has been characterized in great detail in monkeys. However, it is difficult to map the SLF organization in the human brain, and previous diffusion MRI findings have been inconsistent. Using diffusion MRI data from 707 individuals, our probabilistic tractography revealed dorsomedial-to-ventrolateral organization of the three SLF subdivisions and their cortical terminations. Our tractography also suggests limited shared volume between the SLF-I and the cingulum, a controversy in recent literature. The SLF subdivisions also differ in their cognitive associations. As a result, we created a large-scale, high-resolution probabilistic parcellation of the SLF, representing an advancement toward standardizing the mapping of human frontoparietal structural connections for clinical and scientific research.

Tract-based structural and functional connectivity abnormalities in bipolar I disorder

BACKGROUND

Bipolar disorder (BP) is a complex mental illness with poorly understood neural underpinnings. This study aimed to investigate abnormalities in the structural and functional connectivity (FC) of white matter (WM) tracts in BP.

METHODS

Diffusion magnetic resonance imaging (MRI) and resting-state functional MRI data were obtained for 56 patients with BP subtype I (BP-I) and 40 healthy controls (HCs). A total of 72 WM tracts and their corresponding start and end regions were automatically segmented based on diffusion image. The mean diffusivity (MD) and mean fractional anisotropy (FA) of each tract were calculated as proxies of tract-based structural connectivity. FC between the start and end regions of each tract was calculated as a proxy of tract-based FC. The analysis of covariance (ANCOVA) was used to compare the mean MD, FA, and FC values between groups, with multiple comparison correction based Hommel approach.

RESULTS

Compared to the HCs, BP-I patients showed significantly lower FA in the corpus callosum, right and left cingulum, and right superior longitudinal fasciculus III as well as higher MD in the corpus callosum and commissure anterior. Among the tracts with abnormal structural connectivity, only the right SLF-III demonstrated significantly lower FC in the BP-I group than in the control group.

CONCLUSION

BP-I is associated with altered structural connectivity and FC in specific WM tracts, which provides insights into the pathophysiology of this disorder. More research is required to understand the diagnostic and therapeutic implications of these results.

White matter integrity and verbal memory following a first episode of psychosis: A longitudinal study

Psychotic disorders are heterogeneous disorders for which there is evidence of structural and functional brain abnormalities. The role of white matter integrity, often measured via Fractional Anisotropy (FA), has played a controversial role in individuals with a first episode of psychosis (FEP). Similarly, some FEP studies have observed that higher FA is associated with better verbal memory, but others failed to find such an association. Studying the early stages of psychosis represents a promising avenue to overcome previous confounding factors and characterize the disease in its early clinical stages. Eighty individuals with a FEP were recruited from a specialized early intervention program for psychosis alongside 55 non-clinical controls from the community matched for age and sex. Both groups were followed and scanned 4 times: at baseline (within 3 months after program entry), 6 months, 12 months, and 18 months. Tract-Based Spatial Statistics (TBSS) were used on 3.0 Tesla diffusion-weighted images to extract fractional anisotropy values for white matter regions of interest in accordance with the John Hopkins University white-matter tractography atlas. The analysis revealed no significant main effect of group or time, and no significant associations between FA and verbal memory. Overall, differences in FA are small early in the course of illness and longer follow-up periods may be required to identify possible changes during a critical intervention window.

Common and unique white matter fractional anisotropy patterns in patients with schizophrenia with medication-resistant auditory verbal hallucinations: a retrospective tract-based spatial statistics study

Auditory verbal hallucinations (AVHs) are experienced by the majority of patients with schizophrenia and are often resistant to treatment with antipsychotic agents. White matter (WM) tract abnormalities are associated with AVH treatment efficacy. Using a retrospective design, 115 patients with schizophrenia with AVHs, 48 with medication-resistant AVHs and 67 with treatable AVHs, and 70 healthy controls (HCs) were selected from the database of our cohort study for 5-year follow-up assessment. WM tract integrity was measured using tract-based spatial statistics (TBSS) at baseline and after 5 years of antipsychotic agent treatment. The fractional anisotropy (FA) value was used to demonstrate WM tract alterations in patients with schizophrenia with medication-resistant AVHs, in patients with schizophrenia with treatable AVHs, and in HCs. Our data demonstrated that medication-resistant patients showed significantly greater FA values in the corpus callosum (CC) fasciculus at baseline and in the corticospinal tract post-treatment compared to HCs, but the baseline difference in the CC fasciculus was no longer significant after 5 years of antipsychotic agent treatment. The medication-resistant AVH group exhibited greater FA values in the superior longitudinal fasciculus after 5 years of antipsychotic agent treatment. Compared to the HC group, the treatable AVH group exhibited significantly greater FA values in the visual radiation and CC after 5 years of antipsychotic agent treatment. In the medication-resistant and treatable groups, common WM tract abnormalities were noted, as greater FA values were observed in the CC group at baseline compared to the HC group. At the same time, distinct abnormalities were noted, as greater FA values were observed in the superior longitudinal fasciculus, which may contribute to medication-resistant AVHs, whereas abnormalities in the CC fasciculus may contribute to both treatable and medication-resistant AVHs. In the HCs, a decrease in FA values in the posterior CC was observed after 5 years of observation compared to baseline. In summary, patients with treatment-resistant AVHs with schizophrenia and patients with treatable AVHs with schizophrenia have common and distinct abnormalities in the WM tract.

Functional connectotomy of a whole-brain model reveals tumor-induced alterations to neuronal dynamics in glioma patients

Brain tumors can induce pathological changes in neuronal dynamics that are reflected in functional connectivity measures. Here, we use a whole-brain modeling approach to investigate pathological alterations to neuronal activity in glioma patients. By fitting a Hopf whole-brain model to empirical functional connectivity, we investigate glioma-induced changes in optimal model parameters. We observe considerable differences in neuronal dynamics between glioma patients and healthy controls, both on an individual and population-based level. In particular, model parameter estimation suggests that local tumor pathology causes changes in brain dynamics by increasing the influence of interregional interactions on global neuronal activity. Our approach demonstrates that whole-brain models provide valuable insights for understanding glioma-associated alterations in functional connectivity.

Two Axes of White Matter Development

Despite decades of neuroimaging research, how white matter develops along the length of major tracts in humans remains unknown. Here, we identify fundamental patterns of white matter maturation by examining developmental variation along major, long-range cortico-cortical tracts in youth ages 5-23 years using diffusion MRI from three large-scale, cross-sectional datasets (total N = 2,710). Across datasets, we delineate two replicable axes of human white matter development. First, we find a deep-to-superficial axis, in which superficial tract regions near the cortical surface exhibit greater age-related change than deep tract regions. Second, we demonstrate that the development of superficial tract regions aligns with the cortical hierarchy defined by the sensorimotor-association axis, with tract ends adjacent to sensorimotor cortices maturing earlier than those adjacent to association cortices. These results reveal developmental variation along tracts that conventional tract-average analyses have previously obscured, challenging the implicit assumption that white matter tracts mature uniformly along their length. Such developmental variation along tracts may have functional implications, including mitigating ephaptic coupling in densely packed deep tract regions and tuning neural synchrony through hierarchical development in superficial tract regions - ultimately refining neural transmission in youth.

Disruption of structural connectome hierarchy in age-related hearing loss

Introduction

Age-related hearing loss (ARHL) is a common sensory disability among older adults and is considered a risk factor for the development of dementia. Previous work has shown altered brain connectome topology in ARHL, including abnormal nodal strength and clustering coefficient. However, whether ARHL affects the hierarchical organization of structural connectome and how these alterations relate to transcriptomic signatures remain unknown.

Methods

Here, we apply a gradient mapping framework to the structural connectome derived from diffusion magnetic resonance imaging. We focus on the first three structural gradients that reflect distinct hierarchical organization of structural connectome, and assess ARHL-related changes.

Results

We find that, compared to controls, ARHL patients exhibit widespread disruptions of structural connectome organization, spanning from primary sensory areas (e.g., somatomotor network) to high-order association areas (e.g., default mode network). Subsequently, by employing subcortical-weighted gradients derived from weighting cortical gradients by subcortical-cortical connectivity, we observe that ARHL patients show significantly altered subcortical-cortical connectivity in the left caudate, left nucleus accumbens, right hippocampus, and right amygdala. Finally, we investigate the relationship between gene expression and alterations in structural gradients. We observe that these alterations in structural gradients are associated with weighted gene expression profiles, with relevant genes preferentially enriched for inorganic ion transmembrane transport and terms related to regulating biological processes.

Discussion

Taken together, these findings highlight that ARHL is associated with abnormal structural connectome hierarchy and reveal the transcriptomic relevance of these abnormalities, contributing to a richer understanding of the neurobiological substrates in ARHL.

Cognitive load reduces the reinforcement of ventral striatum by anterior insula in taste processing: An fMRI study on self-control

Recent studies have shown that cognitive overload disrupted the affective processing of taste attributes in food-related tasks, which is difficult to explain using dual-system theories with their reflective and impulsive systems (involved in the cognitive and affective processing of stimuli, respectively). The tripartite neurocognitive model proposes an additional interoceptive system that regulates the activities of reflective and impulsive systems. Using this framework, we studied self-control over food choices and hypothesized inferior processing of both affective (taste) and cognitive (health) components of choice-relevant attributes under increased cognitive load. We expected increased cognitive load to decrease the coupling between interoceptive and impulsive systems (represented by anterior insula (AI) and ventral striatum (VS), respectively), and to strengthen decoupling between interoceptive and reflective system (represented by dorsolateral prefrontal cortex (DLPFC)). In an fMRI scanner, 49 participants made 60 food choices requiring self-control (i.e., between a healthier and tastier item) twice: in high (HL) and low working memory load (LL) conditions. We found that functional connectivity between the right AI and VS was weaker in HL compared to LL condition. We also revealed an expected trend towards a stronger negative connectivity between the right AI and DLPFC in HL compared to LL condition. Our findings suggest that cognitively demanding task concurrent to food self-control task overloads AI and reduces the reinforcement of VS by AI. This helps in explaining how and why the affective processing of taste attributes, together with the cognitive processing of health attributes, may be disrupted under cognitive overload.

Connectivity profile and function of uniquely human cortical areas

Determining the brain specializations unique to humans requires directly comparative anatomical information from other primates, especially our closest relatives. Human (Homo sapiens) (m/f), chimpanzee (Pan troglodytes) (f), and rhesus macaque (Macaca mulatta) (m/f) white matter atlases were used to create connectivity blueprints, i.e., descriptions of the cortical grey matter in terms of the connectivity with homologous white matter tracts. This allowed a quantitative comparative of cortical organization across the species. We identified human-unique connectivity profiles concentrated in temporal and parietal cortices, and hominid-unique organization in prefrontal cortex. Functional decoding revealed human-unique hotspots correlated with language processing and social cognition. Overall, our results counter models that assign primacy to prefrontal cortex for human uniqueness.Significance statement Understanding what makes the human brain unique requires direct comparisons with other primates, particularly our closest relatives. Using connectivity blueprints, we compared to cortical organization of the human to that of the macaque and, for the first time, the chimpanzee. This approach revealed human-specific connectivity patterns in the temporal and parietal lobes, regions linked to language and social cognition. These findings challenge traditional views that prioritize the prefrontal cortex in defining human cognitive uniqueness, emphasizing instead the importance of temporal and parietal cortical evolution in shaping our species' abilities.

Apparent Diffusion Coefficient fMRI shines light on white matter resting-state connectivity compared to BOLD

Resting-state functional magnetic resonance imaging (fMRI) is used to derive functional connectivity (FC) between brain regions. Typically, blood oxygen level-dependent (BOLD) contrast is used. However, BOLD's reliance on neurovascular coupling poses challenges in reflecting brain activity accurately, leading to reduced sensitivity in white matter (WM). WM BOLD signals have long been considered physiological noise, although recent evidence shows that both stimulus-evoked and resting-state WM BOLD signals resemble those in gray matter (GM), albeit smaller in amplitude. We introduce apparent diffusion coefficient fMRI (ADC-fMRI) as a promising functional contrast for GM and WM FC, capturing activity-driven neuromorphological fluctuations. Our study compares BOLD-fMRI and ADC-fMRI FC in GM and WM, showing that ADC-fMRI mirrors BOLD-fMRI connectivity in GM, while capturing more robust FC in WM. ADC-fMRI displays higher average clustering and average node strength in WM, and higher inter-subject similarity, compared to BOLD. Taken together, this suggests that ADC-fMRI is a reliable tool for exploring FC that incorporates gray and white matter nodes in a novel way.

Sex-specific effects of intensity and dose of physical activity on BOLD-fMRI cerebrovascular reactivity and cerebral pulsatility

Cerebrovascular reactivity (CVR) and cerebral pulsatility (CP) are important indicators of cerebrovascular health, which are associated with physical activity (PA). While sex differences influence the impact of PA on cerebrovascular health, sex-specific effects of PA intensity and dose on CP and CVR remains unknown. This study aimed to evaluate the sex-specific effects of self-reported PA dose and intensity on CVR and CP. The Human Connectome Project - Aging dataset was used, including 626 participants (350 females, 276 males) aged 36-85. The effect of menopausal status was also assessed. Resting state fMRI data was used to estimate both CVR and CP. Weekly self-reported PA was quantified as metabolic equivalent of task. Females presented a unique non-linear relationship between relative CVR and total PA in the cerebral cortex. Females and menopausal subgroups revealed negative linear relationships with total and walking PA in occipital and cingulate regions. Males exhibited negative linear relationships between total and vigorous PA and CVR in parietal and cingulate regions. Postmenopausal females showed greater reductions across more regions in CP than other groups. Overall, males and females appear to benefit from different amounts and intensities of PA, with menopause status influencing the effect of PA on cerebrovascular health.

T1234: A distortion-matched structural scan solution to misregistration of high resolution fMRI data

PURPOSE

Registration of functional and structural data poses a challenge for high-resolution fMRI studies at 7 T. This study aims to develop a rapid acquisition method that provides distortion-matched, artifact-mitigated structural reference data.

METHODS

We introduce an efficient sequence protocol termed T1234, which offers adjustable distortions. This includes data that match distortions of functional data and data that are free of distortions. This approach involves a T1-weighted 2-inversion 3D-EPI sequence with four combinations of read and phase encoding directions optimized for high-resolution fMRI. A forward Bloch model was used for T1 quantification and protocol optimization. Fifteen participants were scanned at 7 T using both structural and functional protocols to evaluate the use of T1234.

RESULTS

Results from two protocols are presented. A fast distortion-free protocol reliably produced whole-brain segmentations at 0.8 mm isotropic resolution within 3:00-3:40 min. It demonstrates robustness across sessions, participants, and three different 7 T SIEMENS scanners. For a protocol with geometric distortions that matched functional data, T1234 facilitates layer-specific fMRI signal analysis with enhanced laminar precision.

CONCLUSION

This structural mapping approach enables precise registration with fMRI data. T1234 has been successfully implemented, validated, and tested, and is now available to users at our center and at over 50 centers worldwide.

Shaping the structural dynamics of motor learning through cueing during sleep

Enhancing the retention of recent memory traces through sleep reactivation is possible via Targeted memory reactivation (TMR), involving cueing learned material during posttraining sleep. Evidence indicates detectable short-term microstructural changes in the brain within an hour after motor sequence learning, and posttraining sleep is believed to contribute to the consolidation of these motor memories, potentially leading to enduring microstructural changes. In this study, we explored how TMR during posttraining sleep affects performance gains and delayed microstructural remodeling, using both standard diffusion tensor imaging and advanced neurite orientation dispersion and density imaging. Sixty healthy young adults participated in a 5 days protocol, undergoing five diffusion-weighted imaging sessions, pre- and post-two motor sequence training sessions, and after a posttraining night of either regular sleep (RS) or TMR. Results demonstrated rapid skill acquisition on day 1, followed by performance stabilization on day 2, and improvement on day 5, in both RS and TMR groups. (Re)training induced widespread microstructural changes in motor-related areas, initially involving the hippocampus, followed by a delayed engagement of the caudate nucleus. Mean Diffusivity changes were accompanied by increased neurite density index in the putamen, suggesting increased neurite density, while free water fraction reduction indicated glial reorganization. TMR-related structural differences emerged in the dorsolateral prefrontal cortex on day 2 and the right cuneus on day 5, suggesting unique sleep TMR-related neural reorganization patterns. Persistence of practice-related structural changes, although moderated over time, suggests a lasting neural network reorganization, partially mediated by sleep TMR.

The relationship of white matter tract orientation to vascular geometry in the human brain

The white matter of the human brain exhibits highly ordered anisotropic structures of both axonal nerve fibers and cerebral vasculature. Separately, the anisotropic nature of white matter axons and white matter vasculature have been shown to cause an orientation dependence on various MRI contrasts used to study the structure and function of the brain; however, little is known of the relationship between axonal and vascular orientations. Thus, the aim of this study is to compare the orientation between nerve fibers and vasculature within the white matter. To do this, we use diffusion MRI and susceptibility weighted imaging acquired in the same healthy young adult volunteers and analyze the alignment between white matter fibers and blood vessels in different brain regions, and along different pathways, to determine the degree of alignment between these structures. We first describe vascular orientation throughout the brain and note several regions with consistent orientations across individuals. Next, we find that vasculature does not necessarily align with the dominant direction of white matter in many regions, but, due to the presence of crossing fiber populations, does align with at least some white matter within each MRI voxel. Even though the spatial patterns of blood vessels run in parallel to several white matter tracts, they do not do so along the entire pathway, nor for all pathways, suggesting that vasculature does not supply/drain blood in a tract-specific manner. Overall, these findings suggest that the vascular architecture within the white matter is closely related to, but not the same as, the organization of neural pathways. This study contributes to a better understanding of the microstructural arrangement of the brain and may have implications for interpreting neuroimaging data in health and disease.

Along-tract white matter abnormalities and their clinical associations in recent-onset and chronic schizophrenia

Structural impairments in white matter tracts are well-documented in schizophrenia, though their clinical implications remain limited. Most previous studies using diffusion-weighted magnetic resonance imaging (dMRI) and tractography relied on averaged diffusion indices, potentially obscuring localized changes in white matter tracts. Tractometry enables the investigation of localized changes at specific points along white matter tracts. We used dMRI and centerline tractometry to examine along-tract white matter abnormalities in 55 patients with recent-onset schizophrenia, 69 with chronic schizophrenia, and 77 healthy controls. Fractional anisotropy (FA) and peak length were measured at individual points along tract trajectories. Group differences in diffusion indices and their associations with clinical variables, including the Positive and Negative Syndrome Scale (PANSS), were analyzed using linear mixed models and Spearman's rho. In recent-onset schizophrenia, reduced FA was observed in the genu and splenium of the corpus callosum, along with deviations in peak length across multiple white matter tracts. The peak length of association tracts showed a negative correlation with antipsychotic dose. In chronic schizophrenia, widespread reductions in FA and deviations in peak length were identified across various white matter tracts. Decreased FA in commissural tracts was negatively associated with the PANSS negative score, antipsychotic dose, and illness duration. This study identified along-tract white matter abnormalities in recent-onset and chronic schizophrenia and revealed their associations with clinical symptoms. Localized measurements along tract trajectories enhance the detection of clinically relevant abnormalities compared to traditional methods relying on averaged diffusion indices.

Healthy dietary intake diminishes the effect of cerebral small vessel disease on cognitive performance in older adults

Introduction

We evaluated whether regular dietary intake of nutrients commonly found in fish, unsaturated oils, and nuts would moderate the associations between neuroimaging biomarkers of cerebral small vessel disease (cSVD) and cognitive function in older adults.

Methods

Dietary information, Montreal Cognitive Assessment (MoCA) scores, and magnetic resonance imaging (MRI) scans were collected from 71 older adults without dementia (60-86 years). MRI biomarkers of cSVD were calculated for each participant. Multivariate linear regression models were computed using dietary intake as the moderating variable. Covariates included age, sex, and estimated intracranial volume.

Results

Dietary intake moderated the association between several cSVD biomarkers and MoCA scores such that the expected negative association between cSVD biomarkers and cognition was seen at low levels of healthy dietary intake, but not at medium or high levels. A dietary intake by age moderation was not observed.

Discussion

Our findings indicate that healthy dietary intake may confer cognitive reserve against cSVD in older adults.

The control costs of human brain dynamics

The human brain is a complex system with high metabolic demands and extensive connectivity that requires control to balance energy consumption and functional efficiency over time. How this control is manifested on a whole-brain scale is largely unexplored, particularly what the associated costs are. Using the network control theory, here, we introduce a novel concept, time-averaged control energy (TCE), to quantify the cost of controlling human brain dynamics at rest, as measured from functional and diffusion MRI. Importantly, TCE spatially correlates with oxygen metabolism measures from the positron emission tomography, providing insight into the bioenergetic footing of resting-state control. Examining the temporal dimension of control costs, we find that brain state transitions along a hierarchical axis from sensory to association areas are more efficient in terms of control costs and more frequent within hierarchical groups than between. This inverse correlation between temporal control costs and state visits suggests a mechanism for maintaining functional diversity while minimizing energy expenditure. By unpacking the temporal dimension of control costs, we contribute to the neuroscientific understanding of how the brain governs its functionality while managing energy expenses.

Associations between fronto-limbic white matter connections and internalizing symptoms in pediatric demyelinating disease

INTRODUCTION

Children with neuroinflammatory disorders, such as multiple sclerosis (MS), neuromyelitis optica spectrum disorder (NMOSD), and myelin oligodendrocyte glycoprotein-associated disorder (MOGAD), have high rates of anxiety and depression. These symptoms may be linked to disruptions in fronto-limbic white matter (WM) tracts, including the cingulum bundle (CB), inferior fronto-occipital fasciculus (IFOF), and uncinate fasciculus (UF), which support emotional regulation.

METHODS

We studied 33 children with neuroinflammatory disorders and 28 healthy controls. Diffusion tensor imaging and white matter tract integrity maps were generated, focusing on WM tracts of interest (CB, IFOF, UF) and a control tract (acoustic radiation). We examined differences in WM microstructure and internalizing symptoms between high and low symptom groups.

RESULTS

Participants with MS (40%), MOGAD (28%), and NMOSD (25%) reported high levels of internalizing symptoms. MOGAD participants showed lower axonal water fraction compared to MS and controls. Both MS and MOGAD groups exhibited reduced intra-axonal diffusivity and increased extra-axonal diffusivity, indicating demyelination and axonal changes. No significant differences were found between high and low internalizing groups, but higher relapse rates were linked to less WM disruption in those with high internalizing symptoms.

LIMITATIONS

The cross-sectional design limits causal interpretations, and medical covariates may affect WM structure.

CONCLUSION

Neuroinflammatory disorders are linked to fronto-limbic WM changes and high internalizing symptoms. Relapse may influence WM structure and psychological resilience in this population.

Effect of physical exercise training on neural activity during working memory in major depressive disorder

BACKGROUND

Deficits in working memory (WM) are common in patients with Major Depression Disorder (MDD). Previous research mainly in healthy adults indicated that physical exercise training may improve cognitive functions by stimulating neuronal plasticity particularly in hippocampal structures. Thus, the goal of this functional Magnetic Resonance Imaging (fMRI) study was to examine alterations in neuronal activity during a WM task and to investigate changes in brain volume and functioning following a physical exercise training in patients with MDD with a specific focus on hippocampal structures.

METHODS

86 (39 female) MDD outpatients (average age 37.3), diagnosed by clinical psychologists, were randomly assigned to one of three groups for a 12-week intervention: High intensity exercise training (HEX), low intensity exercise training (LEX) or waiting list control group (WL). An n-back task (with WM loads of 0, 1, 2, and 3) during fMRI was conducted before and after interventions/waiting period.

RESULTS

Both exercise groups showed better performance and shorter reaction times at higher WM loads after 12-weeks of physical exercise training. Specifically in the HEX, we found an improvement in physical fitness and an increase in neural activation in the left hippocampus as compared to the WL following the exercise training. Training-related structural volume changes in gray matter or hippocampus were not detected.

CONCLUSIONS

Our results partly support the hypothesis that physical exercise training positively affects WM functions by improving neuronal plasticity in hippocampal regions. Exercise training seems to be a promising intervention to improve deficient WM performance in patients with MDD.

CLINICAL TRIALS REGISTRATION NAME

Neurobiological correlates and mechanisms of the augmentation of psychotherapy with endurance exercise in mild to moderate depression - SPeED, http://apps.who.int/trialsearch/Trial2.aspx?TrialID=DRKS00008869, DRKS00008869.