Blood oxygen level dependent (BOLD) fMRI reports brain activity by measuring the vascular response to neural activity mediated through neurovascular coupling. Theoretical modeling of neurovascular coupling suggests its effect as a low-pass filter that cuts off at <0.2Hz. However, recent evidence suggests that BOLD fluctuations may also contain high frequency components. From a different perspective to address the origin of high-frequency BOLD signals in the rat brain, we examined the BOLD and local field potential (LFP) responses to visceral stimulation (electrical stimulation of the stomach or the vagus nerve), in comparison with the corresponding responses to commonly used sensory stimulation, such as forepaw stimulation. We report herein that visceral (forestomach and vagal nerve) stimulation can induce high-frequency (up to 0.8Hz) BOLD responses. The neuronal origins of such responses are different from those underlying the responses to forepaw stimulation, and likely modulate hemodynamic fluctuations through a more rapid mechanism of vascular control.
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