Fig. 3: Implantable radiofrequency coils and MR-compatible electrophysiological recording in rodent fMRI.

a–d Optogenetically evoked BOLD with implantable inductively coupled detector. a Schematic drawing of two inductive coils with an optical fiber inserted into the right forepaw somatosensory cortex (blue). A representative wide-field fluorescence image illustrates ChR2-mCherry expression. b Averaged time course (top) and normalized spatiotemporal map (bottom) BOLD responses induced directly by optogenetic stimulation in right forepaw somatosensory cortex (right) and projected left hemisphere (left). c BOLD percentage-change time courses (top) and maps (bottom) for each epoch in each voxel along cortical depth on both hemispheres (n = 3). Gray lines indicate light stimulation. d The comparison between both hemispheres shows significantly higher tSNR in images acquired with (blue) implanted inductive coils over images acquired without (red) implanted inductive coils (paired-sample t-test, ***p < 0.001, **p < 0.01 for the gray shadow, upper panel 0–0.8 mm, lower panel 0–1.1 mm, n = 3 rats, mean ± SD). The asterisks on the right side indicate a 3-fold sensitivity gain. Taken with modifications from [Chen 2022]²⁸. e–g fMRI using MR-compatible electrophysiology recording in un-anesthetized mice. e Design and location of MR-compatible electrocorticogram (ECoG array). Two gold wires (orange) were inserted in the nuchal region for electromyography (EMG) recording. Right panel, the diagram of a multi-electrode ECoG array and its layered construction. FPC flexible printed circuit. f The setup was used to assess brain-wide BOLD activation of non-rapid eye movement (NREM) and rapid eye movement (REM) sleep in mice using simultaneous electrophysiology. Shown are group BOLD activation maps of NREM and REM compared to awake (AW) state (FDR corrected, p < 0.05; n = 46). g Relative ECoG band-limited power in NREM and REM compared to AW state and Pearson’s correlation coefficients (C.C.). The boxes show the first and third quartiles; inner line is the median over sessions; whiskers represent minimum and maximum values (outliers removed). delta (δ), 1–4 Hz; theta (θ), 5–10 Hz; alpha (α), 11–20 Hz; beta (β), 21–40 Hz; gamma (γ), 41–100 Hz. Statistical significance was calculated by two-tailed t test. *p < 0.05; **p < 0.01; ****p < 0.0001; n.s., no significance. Taken from [Yu 2023]⁷⁸.