Acute effects of vagus nerve stimulation parameters on gastric motility assessed with magnetic resonance imaging
(Lu, Cao, Phillips, Powley, Liu, 2020. Neurogastroenterology and Motility, e13853)
Vagus nerve stimulation (VNS) is an emerging bioelectronic therapy for regulating food intake and controlling gastric motility. However, the effects of different VNS parameters and polarity on post-prandial gastric motility remain incompletely characterized. We have found that monophasic VNS biased towards the afferent pathway is potentially more effective for facilitating occlusive contractions than that biased towards the efferent pathway.
(Cao, Lu, Oleson, Phillips, Jaffey, Hendren, Powley, Liu. NeuroImage, 197: 200-211, 2019)
Functional magnetic resonance imaging (fMRI) is commonly thought to be too slow to capture any neural dynamics faster than 0.1 Hz. However, recent findings demonstrate the feasibility of detecting fMRI activity at higher frequencies beyond 0.2 Hz, whereas the origin, reliability, and generalizability of fast fMRI responses are under debate and remain to be confirmed through animal experiments with fMRI and invasive electrophysiology. Here, we acquired single-echo and multi-echo fMRI, as well as local field potentials, from anesthetized rat brains given gastric electrical stimulation modulated at 0.2, 0.4 and 0.8 Hz. Such gastric stimuli could drive widespread fMRI responses at corresponding frequencies from the somatosensory and cingulate cortices. Such fast fMRI responses were linearly dependent on echo times and thus indicative of blood oxygenation level dependent nature (BOLD). Local field potentials recorded during the same gastric stimuli revealed transient and phase-locked broadband neural responses, preceding the fMRI responses by as short as 0.5 sec. Taken together, these results suggest that gastric stimulation can drive widespread and rapid fMRI responses of BOLD and neural origin, lending support to the feasibility of using fMRI to detect rapid changes in neural activity up to 0.8 Hz.
Adaptive and wireless recordings of electrophysiological signals during concurrent MRI
Vagus nerve stimulation promotes gastric emptying
(Lu, Cao, Oleson, Phillips, Ward, Powley, Liu. Neurogastroenterology and Motility, 2018)
Vagal nerve stimulation triggers widespread responses and alters large-scale functional connectivity in the rat brain
(Cao, Lu, Powley, Liu. 2017. PLoS ONE, 12(2): e0189518)
Contrast enhanced MRI of gastric emptying and motility in rats
(Lu, Cao, Oleson, Powley, Liu. 2017. IEEE Trans. Biomed. Engr. 64(11): 2546-2554)
Neural and physiological responses to vagus nerve stimulation in rats
(Cao, Lu, Ward, Powley, Liu. 2017. ISMRM. Magna Cum Laude Award)
Mapping systemic inflammation with manganese-enhanced MRI
(Lu, Cao, Marussich, Hu, Liu. 2017. ISMRM, Magna Cum Laude Award)
We used in vivo manganese-enhanced MRI (MEMRI) to image and assess the increase in calcium influx into immune cells so as to report the cellular responses to systemically LPS-induced inflammation throughout the abdomen. We found that: (1) The contrast enhancement was dose- and time-dependent with variation across organs. (2) An increase in Mn2+ uptake was observed in the liver and the kidney, but not in the spleen or the muscle given inflammation. (3) The inflammation-induced enhancement was dependent on the time after the initial exposure to LPS.