Functional Magnetic Resonance Imaging in Awake Rats: Studies Relevant to Addiction and the Reward Circuitry

Functional magnetic resonance imaging (fMRI) has been used to investigate human and laboratory animal brain reward function using a variety of experimental paradigms. The most popular functional imaging technique relies on the blood oxygen level-dependent (BOLD) contrast mechanism first reported in the anesthetized rat by Seiji Ogawa and coworkers in the early 1990s. A significant advantage of fMRI is that it allows a functional characterization of the awake rodent brain under different treatment and pharmacological conditions. We have performed fMRI of the neural actions of cocaine in awake male and female rats and the lactation stimulus in postpartum rats. Animal studies have the design flexibility to verify results with a multiplicity of invasive brain methods that can inform human work and aid in data interpretations. This review provides a summary of the methods used for fMRI experiments in rats with a special focus on awake imaging methods used in our laboratory, which can be applied to feeding behavior.