Keywords: fMRI Acquisition, fMRI, DIANA, neural

Motivation: Recent reports of DIANA responses open the possibility of non-invasively recording neural activity using fMRI.

Goal(s): We aim to test fast, non-selective MRI to better evaluate the feasibility of capturing DIANA responses in the human brain.

Approach: We develop a fast bSSFP sequence without gradient encoding to record the center of k-space during neural activation with a temporal resolution of 3ms.

Results: We observe MRI response dynamics on the order of tens to hundreds of milliseconds, and compare to simultaneously acquired EEG measurements.

Impact: We tested a fast, non-selective MRI sequence to provide preliminary evidence for direct measurement of neural responses in the human brain, and compare these responses to simultaneously acquired EEG measurements.

Keywords: Bioeffects & Magnetic Fields, Multimodal, Spin-lock, Pulse sequence design, New Signal Preparation Schemes

Motivation: In-vivo use of Spin-lock (SL) rotary MR saturation contrast, despite encouraging phantom studies, raises questions about its sensitivity and practicality in neural magnetic field imaging.

Goal(s): Determine if SL contrast effectively maps human neuronal activation, evaluating its sensitivity and localization against MEG and 3T BOLD-fMRI.

Approach: Thirteen volunteers underwent SL-based scanning during visual stimulation, alongside BOLD and magnetoencephalography, with phantom experiments validating the paradigm and processing pipelines.

Results: Preliminary analysis revealed significant activation in the expected visual region for three subjects in SL contrast maps. Low detection was attributed to sensitivity limits estimated in the phantom, falling below MEG-estimated neural fields.

Impact: We assess Spin-lock 3T MR contrast for human neuronal activation mapping. Promising initial results highlight the need for refinement due to sensitivity limitations in neural field detection, supported by phantom MRI and MEG measures.

Keywords: fMRI Acquisition, Neuro, Neuronal Activity, Line Scan Imaging

Motivation: Exploring the cerebrum's functional organisation and processing is challenging. Functional Magnetic Resonance Imaging (fMRI) measures neuronal activity (NA) noninvasively, but relies on indirect signals related to cerebral haemodynamics.

Goal(s): We rigorously investigate if NA in the human brain can be measured using diffusion-weighted fMRI and Direct Imaging of Neuronal Activity (DIANA).

Approach: We utilise DW-fMRI and DIANA at 3 Tesla to record the responses in the somatosensory cortex following electric stimulation of the digits.

Results: We confirm BOLD responses in somatosensory cortex. Both DW-fMRI and DIANA also show stimulus-locked responses. However, we express concerns regarding electrical stimulation noise artefacts and neuronal inhibition.

Impact: This study advances our understanding of neuronal activity measurement using innovative fMRI techniques. It sheds light on the challenges, potential artefacts, and optimal strategies for precise human brain mapping, which is crucial for both basic research and clinical applications.

Keywords: Task/Intervention Based fMRI, fMRI (task based), DIANA

Motivation: Toi et al. reported a revolutionary approach of direct imaging of neuronal activity (DIANA) by fMRI in anesthetized mice at 9.4 T. However, anesthesia has a profound impact on the central nervous system, leading to modifications in physiological parameters.

Goal(s): Our goal is to investigate Direct Neuronal Activity-related (DIANA) fMRI in awake mice.

Approach: We performed the event-related cerebral functional magnetic resonance imaging and DIANA experiment in habit-trained awake mice.

Results: In response to the electrical stimulation, a statistically significant increase in the DIANA signal was observed in the contralateral S1FL compared with the prestimulus signal (p < 0.005, n = 6 mice). 

Impact: Direct detection of neural activity allows us to better understand the rapid dynamics of neural activity, which will help improve the understanding and diagnosis of neurological diseases.

Keywords: fMRI Acquisition, fMRI, DIANA

Motivation: Direct Imaging of Neuronal Activity (DIANA) was proposed by Toi et al. in Science 2022. Before DIANA can be adopted, key findings must be reproduced.

Goal(s): Independent reproduction of the results shown in supplemental Figure 26 of Toi et al.

Approach: Rats were scanned at 7.0T and 17.2T using a visual paradigm consisting of a 10ms blue flash every 200ms.

Results: No DIANA signal was detected, even though the temporal signal to noise ratio was sufficient to detect signal changes of 0.1%. However, a slow hemodynamic signal, much larger than the expected DIANA signal, was observed between measurements with and without stimulus.

Impact: Our failure to detect a DIANA signal in rat at 7.0T and 17.2T, echo's findings by Hodono et al. (Imaging Neuroscience) and Choi et al. (bioRxiv), indicating DIANA is not ready for use in neuroscientific studies.

Keywords: Probes & Targets, Brain Connectivity

Motivation: A recent study argued that it is possible to detect neuroelectrical potentials using an fMRI scanning approach called DIANA. Although DIANA signals coincide with electrophysiological measurements, no mechanism for the effect was reported

Goal(s): We sought to implement DIANA in order to understand the origins of the reported results.

Approach: We applied variants of the DIANA pulse sequence under test and control conditions, comparing results with simulations.

Results: We observed DIANA signals but show that neural activity is neither necessary nor sufficient for this. Instead, the DIANA signal appears to result largely from nonideal aspects of pulse sequence timing.

Impact: Our study suggests that the DIANA signal arises from an artifact in the line scan pulse sequence. This indicates possible pitfalls in implementing such sequence designs and emphasizes the continuing need for fMRI-based direct readouts of neural activity.

Keywords: Task/Intervention Based fMRI, Modelling, Non-BOLD fMRI, Novel contrast mechanisms

Motivation: Diffusion fMRI explores brain dynamics via water ADC variations from cellular fluctuations, distinct from BOLD imaging as it bypasses neurovascular coupling. Despite its potential, dFMRI remains underexplored in fMRI research.

Goal(s): The goal of this work is to validate the utility of ADC in fMRI.

Approach: Two imaging techniques were utilized: DW-TRSE-EPI and SE-EPI, capturing ADC timecourses and T2-BOLD contrast. The study investigated correlations between a visual paradigm and voxel timecourses.

Results: Voxels exhibiting negative ADC and positive BOLD task responses align within the visual cortex. Likewise, voxels displaying positive ADC and negative BOLD responses predominantly align in the default mode network.

Impact: Diffusion fMRI could serve as a complementary method to BOLD imaging, both exploring neural activity through distinct approaches.

Keywords: Aging, Nerves, quantum sensing

Motivation: The qsMRI has the potential for non-invasive detection of neuronal electrical activities (action potentials or firings) in the human brain. This emerging technique, however, is still in infant stage and needs more studies to show its potentials.

Goal(s): This study explores whether qsMRI detects the change in neuronal firings during a finger-tapping task in a wide range of ages.

Approach: A group of healthy subjects (27–84 years old) were studied on a 3T MRI scanner, using three tasks: finger-tapping, no tapping, and resting state.

Results: Firing rate varied with age, and older people showed higher firing rate during tapping than resting.

Impact: These positive results further demonstrated the potential of qsMRI to detect neuronal firings in humans, and will encourage researchers to use the technique in a wide range of studies on brain functions and neurological disorders including aging and Alzheimer’s disease.