Neuroimaging techniques

Neuroimaging techniques—for example, electroencephalographic (EEG), optical (fNIRS, near infrared spectroscopy), and magnetic resonance imaging (MRI)—make it possible to study brain function and structure, and have made an essential contribution to the diagnosis and treatment of neurological and cognitive problems. The EEG detects electrical activity in the brain using electrodes attached to the scalp. From the electrical signals of the EEG, it is possible to construct maps of the oscillatory brain activity, according to its frequency, for the assessment of brain function during information processing or at rest. fNIRS is an optical neuroimaging technique that measures brain's metabolic response. From the fNIRS signal, it is possible to build brain function maps by measuring the cerebral cortex's optical changes. Magnetic resonance imaging is another neuroimaging technique that uses a magnetic field and radio waves to generate images of the brain's function and structure without using radioactive tracers. In this chapter, these three techniques are discussed. In the first section of this chapter, the electrical signals produced by the brain are reviewed. These signals are involved in many cognitive and behavioral processes, but will only be reviewed when subjects are at rest. The second section of this chapter introduces the fNIRS technique, including the physical and physiological principles underlying optical imaging and the technical considerations for conducting an fNIRS experiment. The last section corresponds to the generation of conventional and functional magnetic resonance imaging (MRI), starting from the basic physical principles and ending with its immediate clinical application.