Resting-state functional connectivity of primary somatosensory cortices in urethane anesthetized rats

INTRODUCTION Spontaneous low frequency fMRI fluctuations measured during resting-state have been shown to provide important information on spontaneous neuronal activity and the functional organization of the brain [1]. Although many resting-state fMRI studies have been performed on human subjects, only a handful of studies have been conducted in rat models. The major concern in rodents and in animal studies in general is the use of anesthesia. Previously medetomidine hydrochloride (Domitor) anesthesia has been reported to be feasible for resting-state fMRI experiments in rats [2,3,4]. Urethane anesthesia, on the other hand, has been shown to be suitable for fMRI and local field potential (LFP) experiments [5], but to our knowledge the feasibility of urethane for resting-state fMRI studies has not been evaluated. In this study, we measured fMRI from rats under urethane anesthesia during electrical forepaw stimulation and resting-state in order to evaluate the feasibility of urethane for restingstate fMRI experiments in rodents. The electrical forepaw stimulation was used to functionally locate the region of interest, primary somatosensory cortex (SI), which was used as the “seed” region for calculating resting-state correlation maps. SI was chosen as the region of interest based on the previously reported bilateral correlation of these areas in resting-state under Domitor anesthesia and because the functional location of SI can be robustly detected with fMRI using electrical forepaw stimulation.