Fundamentals of MRI for assessing brain function and metabolism

Introduction Modern neuroimaging has revolutionized the study of brain structure and function. In particular, advanced magnetic resonance imaging (MRI) techniques allow the non-invasive collection of functional and metabolic data in human subjects that were previously restricted to invasive animal model systems. In this chapter, we review three of the most important and topical advanced MRI techniques. We first consider functional MRI (fMRI), which permits dynamic evaluation of neural activity in specific brain regions. Numerous applications for fMRI exist in sleep-related research, including examination of the neural correlates of sleep states and the consequences of sleep disturbance for waking neural function [1]. We then discuss diffusion tensor imaging (DTI), which illuminates the structure of cerebral white matter, and demonstrates the white matter connections between gray matter structures. DTI may thereby allow the identification of subtle white matter abnormalities which contribute to sleep-related disorders [2, 3]. We conclude with an introduction to magnetic resonance spectroscopy (MRS), a non-invasive method for the evaluation of brain chemistry. MRS may permit the demonstration of subtle metabolic deficits that accompany sleep disturbance [4, 5].