Keum, J.-Y. | Search bioRxiv

bioRxiv2025

Update on the reproduction and interpretation of DIANA fMRI

Three years ago, our group reported direct imaging of neuronal activity (DIANA) with high spatiotemporal resolution, but its reproducibility and signal origin remain controversial. Here, we report the results of our reproduction experiments of DIANA fMRI performed to date using forelimb electrical stimulation at various magnetic field strengths in anesthetized mice, along with the characteristics of DIANA signal, called the pseudo-steady state (PSS). Theoretical analysis and Bloch simulations demonstrated that the spatial location and temporal phase of PSS oscillations are primarily determined by frequency-offset, and that their spatiotemporal superposition can generate peak signals in specific regions at specific timing that closely resemble DIANA signals. These findings suggest that if PSS oscillations are the primary source of DIANA signals, it may be premature to interpret them as neuronal responses to sensory stimulation. Further studies are needed to clarify the relationship between DIANA signals and brain activation.

neuroscience↗

bioRxiv2024

Direct imaging of neural activity reveals neural circuits via spatiotemporal activation mapping

Two years ago, our group reported direct imaging of neuronal activity (DIANA), a functional magnetic resonance imaging (fMRI) technique that directly detects neuronal activity at high spatiotemporal resolution. In this study, we successfully reproduced the DIANA response in medetomidine-anesthetized mice using forelimb electrical stimulation at 11.7 T. More importantly, we showed that multiple neural circuits can be effectively revealed by DIANA fMRI through spatiotemporal activation mapping. The spatiotemporal activation mapping proposed here utilizes the temporal information of the DIANA response, that is, the time when the DIANA response reaches its peak, which is a unique feature that distinguishes it from the activation mapping method used in existing fMRI. Based on DIANA activation areas, we identified several neural circuits involved in forelimb sensory processing in the somatosensory network, which includes multiple brain regions: ventral posterolateral nucleus of the thalamus (VPL), posteromedial thalamic nucleus (POm), forelimb primary somatosensory cortex (S1FL), secondary somatosensory cortex (S2), primary motor cortex (M1), and secondary motor cortex (M2). Additionally, we also identified a pain-related neural circuit involving brain regions of the anterior cingulate cortex (ACC) and mediodorsal nucleus (MD). Interestingly, the spatiotemporal activation mapping also allowed us to identify subregions with different DIANA response times within the same functional region (e.g., VPL, POm, S1FL, and S2). Our study highlights the potential of DIANA fMRI to advance our understanding of sensory information processing throughout the brain and to provide insight into the spatiotemporal dynamics of brain networks at the level of neural circuits.

neuroscience↗