This chapter tackles positron emission tomography (PET), a functional neuroimaging technique that revolutionized brain imaging in the 1970s by providing the first colorful maps of brain activity. Beginning with its historical development from Hans Berger’s early hemodynamic measurements to modern scanners, the chapter examines how PET visualizes metabolic processes by tracking radioactively labeled tracers in the bloodstream. Unlike structural imaging methods, PET detects gamma rays emitted when positrons from the radiotracer collide with electrons, allowing researchers to measure regional changes in blood flow, glucose metabolism, and neurotransmitter activity related to cognitive processes. The chapter details practical aspects of PET studies, including experimental design, data acquisition, image reconstruction techniques, and visualization methods like subtraction analysis for mapping task-related brain activity. While MRI-based techniques have supplanted PET for many cognitive neuroscience applications, PET remains invaluable for certain investigations due to its unique ability to label diverse compounds, particularly for studying neuropsychiatric disorders, neurotransmitter systems, and metabolic processes in diseases like Alzheimer’s and epilepsy.

Chapter 5 examines functional magnetic resonance imaging (fMRI) as a transformative neuroimaging technique that maps brain activity by detecting changes in blood oxygenation. The chapter traces fMRI’s development from Angelo Mosso’s 19th-century observations of blood-flow changes during neural activity to Seiji Ogawa’s pioneering work with blood oxygenation level-dependent (BOLD) contrast in the 1990s. It discusses the neurophysiological basis of the BOLD signal and how increased neural activity triggers disproportionate increases in cerebral blood flow relative to oxygen metabolism, creating measurable magnetic susceptibility differences. The text analyzes the temporal profile of the hemodynamic response, with its characteristic delay, peak, and undershoot, emphasizing its implications for experimental design. Considerable attention is given to the methodological complexities of fMRI research: preprocessing steps (slice-timing correction, motion correction, coregistration), statistical analysis approaches (including voxel-wise comparisons and region-of-interest analyses), and techniques for examining functional connectivity between brain regions. By evaluating fMRI’s comparative advantages, which is exceptional spatial precision and its noninvasive nature, alongside its limitations in temporal resolution and indirect measurement of neural activity, the chapter discusses fMRI as a powerful, albeit technically demanding, tool that provides unique insights into functional brain organization while requiring rigorous experimental design and statistical analysis.