Transcranial Brain Stimulation and Magnetic Resonance Spectroscopy

Abstract Proton (hydrogen 1 [1H]) magnetic resonance spectroscopy (1H-MRS) can be used to noninvasively quantify the regional levels of glutamate and gamma aminobutyric acid (GABA) within a given brain area. Since glutamate and GABA are two major neurotransmitters, 1H-MRS is an important technique to understand the neurophysiological basis of noninvasive transcranial brain stimulation (NTBS) approaches. However, like all complex methods, there are important methodological issues that should be considered in NIBS-MRS studies. This chapter aims both to take a snapshot of the current state of the field and equip the reader with sufficient information to understand the potential, and limitations of MRS as a technique to study NIBS. In the first part of this chapter, we will discuss the technical basis of the technique and give an overview of the essential biochemistry of the quantified neurochemicals. In the second part, we summarize what 1H-MRS studies have shown about the neurophysiological effects of NIBS. Some clear patterns emerge, but other aspects of the literature are less clear. We will conclude by defining outstanding questions to be tackled in future studies.