Biology subjects

Im, G. H.

Publications and source records attributed to Im, G. H..

4 recordsLinked to original sources

bioRxiv2026

Deafness rapidly reorganizes functional brain networks in adult mice

Sensory loss triggers crossmodal reorganization across sensory modalities, and accumulating evidence indicates that this adaptive capacity persists into adulthood. However, the global organizing principles of such plasticity remain poorly understood, as conventional animal model approaches do not permit longitudinal, whole-brain measurements. Here, we use ultra-high-field (15.2T) BOLD fMRI to map deafening-induced functional reorganization across the entire brain in young adult mice. Within one week of deafening, the auditory cortex is recruited by somatosensory and visual inputs, while stimulus-evoked responses are potentiated in the spared sensory pathways. Reorganization extends beyond sensory cortices to higher-order association areas, including anterior cingulate, retrosplenial, and posterior parietal cortices. Resting-state fMRI further reveals strengthened coupling both within sensory systems and between sensory systems and a default mode-like network. These findings demonstrate that adult-onset deafness rapidly reorganizes functional brain networks and further implicate the default mode-like network as a potential mediator of crossmodal integration.

neuroscience↗

bioRxiv2025

Longitudinal Resting-State fMRI of Awake Mice During Habituation: Stress, Head Motion, and Functional Connectivity

Awake mouse fMRI is a powerful tool for both neuroscience and translational research. To minimize head motion during scanning, habituation under physical restraint is commonly used. However, it remains unclear how stress levels and head motion evolve during habituation, particularly within the MRI environment. To address this, we repeatedly measured plasma corticosterone (CORT) levels in three groups of mice - controls, mice habituated outside the MRI magnet, and mice habituated within the fMRI environment - and acquired longitudinal resting-state fMRI data daily during an eight-day habituation period and again 15 days post-habituation at 15.2 T. We found that CORT levels initially increased by approximately twofold and gradually decreased during habituation outside the magnet, whereas in mice habituated within the fMRI environment, CORT levels increased two- to fourfold and remained elevated throughout the habituation period. One week after habituation, CORT levels returned to baseline in both groups. Throughout all resting-state fMRI scanning sessions, head motion and functional connectivity remained stable, likely due to the well-designed restraint cradle that permitted paw movement. These results suggest that additional habituation days do not further reduce stress, provided that head motion remains within acceptable limits.

neuroscience↗

bioRxiv2023

No Replication of Direct Neuronal Activity-related (DIANA) fMRI in Anesthetized Mice

Direct imaging of neuronal activity (DIANA) by fMRI could be a revolutionary approach for advancing systems neuroscience research. To independently replicate this observation, we performed fMRI experiments in anesthetized mice. The BOLD response to whisker stimulation was reliably detected in the primary barrel cortex before and after DIANA experiments; however, no direct neuronal activity-like fMRI peak was observed in data of individual animals with the 50-300 trials. Extensively averaged data involving 1,050 trials in 6 mice showed a flat baseline and no detectable neuronal activity-like fMRI peak. However, spurious, non-replicable peaks were found when using a small number of trials, and artifactual peaks were detected when some outlier-like trials were excluded. Further, no detectable DIANA peak was observed in the BOLD-responding thalamus from the selected trials with the neuronal activity-like reference function in the barrel cortex. Thus, we were unable to replicate the previously reported results without data pre-selection.

neuroscience↗

bioRxiv2022

Whole-brain mapping of effective connectivity by fMRI with cortex-wide patterned optogenetics

Functional magnetic resonance imaging (fMRI) with optogenetic neural manipulation is a powerful tool that enables brain-wide mapping of effective functional networks. To achieve flexible manipulation of neural excitation throughout the mouse cortex, we incorporated spatiotemporal programmable optogenetic stimuli generated by a digital micromirror device into an MR scanner via an optical fiber bundle for the first time. This approach offered versatility in space and time in planning the photostimulation pattern, combined with in situ optical imaging and cell-type or circuit-specific genetic targeting in individual mice. Brain-wide effective connectivity obtained by fMRI with optogenetic stimulation of atlas-based cortical regions is generally congruent with anatomically defined axonal tracing data but is affected by the types of anesthetics that act selectively on specific connections. fMRI combined with flexible optogenetics opens a new path to investigate dynamic changes in functional brain states in the same animal through high-throughput brain-wide effective connectivity mapping.

neuroscience↗