Positron emission tomography (PET) measures brain activity by detecting gamma rays emitted from radioactive tracers injected into the bloodstream. Different tracers can measure blood flow (an index of neural activity), glucose metabolism, and neurotransmitter receptor binding. While largely superseded by fMRI for measuring brain activation, PET retains unique advantages for studying neurotransmitter systems, receptor occupancy, and molecular processes that fMRI cannot assess.
Contributions to Cognitive Neuroscience
PET pioneered functional brain imaging in the 1980s, producing the first maps of brain activity during cognitive tasks. The landmark studies of Petersen, Fox, Posner, and Raichle (1988) used PET to map the brain areas involved in reading, generating words, and semantic processing. PET remains essential for studying dopamine, serotonin, and other neurotransmitter systems in health and disease — measuring receptor density, neurotransmitter release, and the effects of pharmacological interventions.