Update on the reproduction and interpretation of DIANA fMRI

Abstract

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.