Resting-state fMRI has emerged as a potential method to identify diagnostic bio-imaging markers of a broad spectrum of neurological disorders by measuring the low-frequency fluctuation (LFF) correlation features of diseased brains. Due to the fMRI signal’s indirect coupling to neuronal activity, a fundamental challenge of rs- fMRI mapping is how to extract the true “functional connectivity” feature across cortices with circuit specificity. Both direct corticocortical connections, e.g. callosal projections, and subcortical neuromodulatory projections can modulate rs-fMRI connectivity with converging effects on neuro-glio-vascular (NGV) interactions. Also, au- tonomic regulation on gliovascular dynamics further confounds rs-fMRI LFF when interpreting the brain dam- age with vascular impairment in various cerebrovascular diseases. We propose to implement line-scanning and single-vessel fMRI methods in a multi-modal platform to dissect laminar and vascular-specific rs-fMRI LFF and decipher NGV signaling underlying rs-fMRI LFF. Here, we will focus on elucidating the transcallosal circuit- based interhemispheric rs-fMRI LFF correlation in the normal and diseased mouse model with hypoperfusion- induced cerebrovascular white matter injury in the corpus callosum. Three aims will be addressed: 1). We will investigate the causal linkage between laminar-specific bilateral LFF and transcallosal projection. Two hypoth- eses will be tested: i). Layer-specific transcallosal projections determine bilateral LFF laminar correlation pat- terns, and ii). Callosal-driven laminar LFF holds distinct oscillation features from brain state-dependent global LFF. 2). We will differentiate the NGV signaling of callosal-specific and global vascular LFF using multi-modal fMRI. Also, we will test two hypotheses: i). Callosal projection neuron-specific oscillation mediates circuit-spe- cific bilateral LFF, and ii). Distinct astrocytic Ca2+ signals coupled to either callosal projection neuronal activity or global neuromodulation contribute to different forms of LFF correlation. 3). We will specify callosal-specific and global vascular LFF in the hypoperfusion-induced white matter injury mouse model. We will test if hy- poperfusion-induced cerebral flow changes alter global vascular LFF and hypoperfusion-induced injury in the corpus callosum leads to altered bilateral rs-fMRI connectivity. This proposal aims to reveal the mechanistic NGV regulation of circuit-specific rs-fMRI LFF and apply novel rs-fMRI methods in the diseased mouse model to set the foundation to translate specific LFF correlation patterns as potential biomarkers of circuit dysfunction or vascular impairment in pathological brains.

An ongoing challenge of functional connectivity mapping with resting-state (rs) fMRI is to elucidate the circuit- specific versus global vascular correlation. Animal fMRI has played a critical role in mapping brain function with multi-modal neuro-techniques across different spatial scales. This proposal aims to apply novel rs-fMRI methods to specify circuit-specific rs-fMRI signals and examine circuit dysfunction in a mouse model with cerebrovascular white matter injury. We expect to improve the mechanistic understanding of circuit-specific rs-fMRI connectivity and to specify altered rs-fMRI signals as biomarkers of pathological circuit function or cerebrovascular impair- ments.