Keywords: fMRI Acquisition, fMRI

Motivation: Neuronal activity induces vasodilation in local arterioles that propagates to upstream large arteries, but the furthest detectable arterial dilation from the site of neuronal activity remains unknown.

Goal(s): Detecting blood velocity responses at far upstream branches of the Posterior Cerebral Artery induced by a visual stimulus.

Approach: In this study, a functional phase-contrast MRA technique was combined with a commonly used block-design stimulation paradigm to detect blood velocity responses.

Results: About 10–20% velocity increases at the P2 segments of the Posterior Cerebral Artery were robustly observed.

Impact: We demonstrate that neuronal activity-induced velocity response can propagate to large feeding arteries 6–7 cm from the visual cortex. The spatial and temporal properties of this propagation are important for understanding neurovascular coupling, autoregulation, and human fMRI.

Keywords: fMRI Acquisition, fMRI

Motivation: DiSpect can trace blood draining from the capillary bed through the cerebral venous system and map venous territories.

Goal(s): Determine whether DiSpect can detect blood flow changes in the veins during neural activation.

Approach: DiSpect was performed during a motor cortex task and at baseline for two subjects, each with two repeats to ensure consistency and repeatability.

Results: Modulation and redistribution of flow were observed during the task, specifically in veins near the BOLD fMRI activated regions. The measurements showed good repeatability for both subjects.

Impact: BOLD contrast is affected by a complex interplay of several physiological processes. DiSpect measures changes in venous blood flow dynamics during neural activation and can potentially help to better understand the venous sources of the BOLD signal.

Keywords: fMRI Acquisition, Data Acquisition, fMRI

Motivation: Achieving millisecond-scale temporal resolution MRI has the potential to provide exciting insights into fast functional/physiological processes of the brain. 

Goal(s): Develop a new acquisition method, EPTIMA, that can achieve millisecond-scale temporal resolution, while improving efficiency by acquiring a time-series trial of 2D-images in a single excitation for high robustness to physiological-noise/motion.

Approach: EPTIMA captures fast temporal dynamics occurring within the readout by measuring the rate at which the baseline signal evolution is changing, and employs spatiotemporal encodings to acquire a complete time-series trial in a single-excitation.

Results: EPTIMA can image rapid electric current changes in a phantom and resolve stable phase/magnitude changes in-vivo.

Impact: A new acquisition, EPTIMA, was developed to achieve millisecond-scale temporal resolution and to image ultra-fast dynamic processes of human brain. It improves efficiency by acquiring a time-series trial of 2D-images in a single excitation with high robustness to motion/physiological noises.

Keywords: fMRI Acquisition, CEST & MT, CEST-fMRI

Motivation: Conventional fMRI techniques indirectly map neural activity through the BOLD effect, but there is a need for a methodology to directly detect dynamic changes in neurotransmitter levels.

Goal(s): Our goal was to detect the increase in glutamate concentration in the human brain during a visual task based on CEST.

Approach: We performed two tailored experiments on a 3T scanner and used a 4-regressor general linear model (GLM) analysis to extract the metabolite effects from CEST-fMRI signals.

Results: A ~0.12% metabolite effect was detected at glutamate-proximal frequency offsets, consistent with our simulation under a 3% increase in glutamate concentrations during brain activity.

Impact: Our study successfully revealed the mechanism behind CEST-fMRI and demonstrated its ability to detect dynamic changes in glutamate concentrations during visual stimulation. The CEST-fMRI methodology enables the investigation of neurotransmitter changes, potentially becoming an imaging modality that guides neuroscience research.

Keywords: Spectroscopy, Spectroscopy, functional MRS

Motivation: Functional magnetic resonance spectroscopy (fMRS) shows promise in studying task-related metabolite changes but has been largely confined to single-voxel.

Goal(s): To evaluate two-voxel fMRS at 7 T to measure simultaneous bilateral metabolite changes during a unilateral motor task. 

Approach:  A modified Hadamard-encoded MRS scheme with dynamic fMRS spectral-temporal fitting for analysis was employed.

Results: Distinct patterns of BOLD activation in contra- and ipsilateral VOIs were detected with significant increases in Glutamate (Glu) in either VOI during a unilateral task

Impact: We demonstrate the feasibility of simultaneous two-voxel MRS to detect bilateral glutamate changes in response to a unilateral motor task. This approach holds promise to increase our understanding of the neurochemical underpinnings of fMRI signals across interconnected brain regions.

Keywords: Functional Connectivity, Quantitative Susceptibility mapping, Brain connectivity, resting-state fQSM

Motivation: Task-based functional Quantitative Susceptibility Mapping (fQSM) shows more localized brain activations than fMRI. Resting-state fMRI reveals brain connectivity networks but resting-state analysis of QSM has not yet been performed and may provide complementary information.

Goal(s): To perform a resting-state functional analysis using QSM (rsfQSM) and compare it to rsfMRI, focusing on the Default Mode Network (DMN).

Approach: We used seed-based and ICA-based analyses for rsfQSM and assessed the similarity of the DMN to that in rsfMRI with quantitative metrics.

Results: The DMN was detected in rsfQSM with spatial similarities to the DMN in rsfMRI. rsfQSM showed weaker and less extensive functional connectivity.

Impact: We computed resting-state functional connectivity from magnetic susceptibility maps for the first time, revealing similarities in the default-mode network compared to rsfMRI. This paves the way for new QSM-based explorations of brain function to potentially deepen understanding of neurological diseases.

Keywords: Task/Intervention Based fMRI, Brain

Motivation:  Theory and modelling suggest that detection of neuronal activity may be feasible using phase sensitive MRI methods.

Goal(s): To demonstrate successful application of phase-based MREPT to functional tasks in brain

Approach: Using bFFE optimised for fast acquisition, data were acquired from 5 participants undertaking visual stimulation or somatosensory stimulation. Electrical conductivity values extracted from phase images were fitted with the measured stimulus response function.

Results:   Images showed consistent activation of visual circuitry (~0.1 S/m) in both grey and white matter with similar circuit responses to somatosensory stimulation. Conductivity increased with stimulus duration or increased contrast and was faster, temporally, than BOLD.

Impact: Functional conductivity imaging (funCI) reveals activity in both grey and white matter. The sensitivity, repeatability and time course of funCI shows that MRI can detect brain activation beyond changes in blood supply.

Keywords: Functional Connectivity, Brain Connectivity, brain chart, brain atlas, lifespan, connectomics

Motivation: The normative developmental and aging trajectory of the functional connectome in the human brain remains unknown.

Goal(s): To establish the normative growth trajectory of functional connectome from the largest, quality-controlled multimodal neuroimaging dataset.

Approach: We aggregated 33,809 task-free fMRI scans from 32,328 individuals aged 32 postmenstrual weeks to 80 years from 119 global sites, and quantified lifespan growth charts using generalized additive models for location, scale, and shape (GAMLSS).

Results: We uncovered nonlinear connectome growth at the whole cortex, system, and regional levels, identified critical developmental inflection points, and demonstrated substantial individual heterogeneities in patients with ASD and patients with MDD.

Impact: Our findings elucidate for the first time the lifespan evolution of the functional connectome and serve as a normative reference for quantifying individual variation in patients with neuropsychiatric disorders.

Keywords: Epilepsy, Bioeffects & Magnetic Fields, Spin-lock, Novel Contrast Mechanisms

Motivation: Delineation of the seizure onset zone (SOZ) in surgical planning for drug-resistant epilepsy requires invasive procedures. The Stimulus-Induced Rotary Saturation (SIRS) sequence targets biomagnetic field associated with epileptic discharges.

Goal(s): To evaluate the efficiency of SIRS in epilepsy lateralization using high-frequency oscillations (HFOs) as biomarkers and compare it with EEG and clinical seizure semiology.

Approach: We investigated 11 epilepsy patients using SIRS at a 120 Hz spin-lock frequency, assessing the localizing value at hemispheric and lobar levels.

Results: SIRS-identified activations were above threshold in 8 of 11 patients, offering potential for improved SOZ localization. Hemispheric concordance was found with EEG in 7 cases.

Impact: Spin-lock based rotary saturation imaging lateralized brain areas in epilepsy patients with negative MRI findings in concordance with EEG and seizure semiology. Combined with state-of-the-art non-invasive methods such as EEG, it offers potential for improved seizure lateralization.

Keywords: Head & Neck/ENT, fMRI (resting state)

Motivation: Standard fMRI techniques are unable to image the nasal cavity due to strong susceptibility artefacts.

Goal(s): Our goal is to exploit ultrashort or zero echo time imaging to study functional connectivity of the nose.

Approach: Resting-state fMRI was performed on 5 humans at 7T and 1 mouse at 9.4T. Independent component analysis (ICA) was performed, and ICA signals were analyzed within the context of other physiological signals. 

Results: Highly reproducible nose networks were observed in humans. The signal of one network strongly correlated with the autonomic nervous system activity. A pronounced nose network was also observed in the mouse.

Impact: Ultrashort and zero echo time fMRI enables unprecedented performance for detecting functional nose networks providing the means to study nose activity and system-wide connections between central and peripheral nervous systems not currently possible with standard fMRI for the first time.