Vagus nerve stimulation (VNS) is an emerging treatment for brain disorders, such as depression and epilepsy. However, its efficacy varies, and its mechanism is unclear. Prior studies have used functional MRI (fMRI) to map brain activations with VNS in human brains but yielded inconsistent findings. The source of the inconsistency might be attributed to the complex temporal characteristics of VNS-evoked responses that cannot be fully explained by simplified response models. Using a rat model, we aimed to characterize the VNS evoked responses at the level of brain networks without assuming any priori response model. Our results suggest that the repetitive and block-wise stimulation to the vagus nerve induces activations at widespread brain regions. The responses are complex and variable across regions, much beyond what can be described with conventionally assumed HRF.