Abstract
Pupillometry, a noninvasive measure of arousal, complements human functional MRI (fMRI) to detect periods of variable cognitive processing and identify networks that relate to particular attentional states. Even under anesthesia, pupil dynamics correlate with brain-state fluctuations, and extended dilations mark the transition to more arousable states. However, cross-scale neuronal activation patterns are seldom linked to brain state-dependent pupil dynamics. Here, we complemented resting-state fMRI in rats with cortical calcium recording (GCaMP-mediated) and pupillometry to tackle the linkage between brain-state changes and neural dynamics across different scales. This multimodal platform allowed us to identify a global brain network that covaried with pupil size, which served to generate an index indicative of the brain-state fluctuation during anesthesia. Besides, a specific correlation pattern was detected in the brainstem, at a location consistent with noradrenergic cell group 5 (A5), which appeared to be dependent on the coupling between different frequencies of cortical activity, possibly further indicating particular brain-state dynamics. The multimodal fMRI combining concurrent calcium recordings and pupillometry enables tracking brain state-dependent pupil dynamics and identifying unique cross-scale neuronal dynamic patterns under anesthesia.
Highlights
Pupillometry, a noninvasive measure of arousal, complements human functional MRI to detect periods of variable cognitive processing and identify networks that relate to particular attentional states
Based on the rs-functional MRI (fMRI) signal and its correlation with pupil dilations, we identified the presence of oscillatory brain states under anesthesia, which were represented by neuronal calcium dynamics
Alternation between brain states was evidenced by the transition from constricted to dilated pupil or vice versa, which showed a strong correlation with the whole-brain fMRI signal fluctuation and with the neuronal calcium signal oscillation
Summary
Pupillometry, a noninvasive measure of arousal, complements human functional MRI (fMRI) to detect periods of variable cognitive processing and identify networks that relate to particular attentional states. We complemented resting-state fMRI in rats with cortical calcium recording (GCaMP-mediated) and pupillometry to tackle the linkage between brain-state changes and neural dynamics across different scales. This multimodal platform allowed us to identify a global brain network that covaried with pupil size, which served to generate an index indicative of the brain-state fluctuation during anesthesia. Experiments performed in rats have revealed key global signatures that precede brain-state changes during anesthesia by measuring the fMRI signal in parallel to the calciumdependent neuronal and astrocytic activity [4], which indicates the potential of multimodal fMRI platforms to be applied in behaving rodents to track different brain states.
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