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 While largely superseded by fMRI for measuring brain activation, PET retains unique advantages for studying neurotransmitter systems, receptor occupancy, and molecular processes that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.
Key Structures
- Whole brain (measures metabolic activity, blood flow, or neurotransmitter receptor binding in any region)
- fMRI — Functional magnetic resonance imaging, a neuroimaging technique that measures brain activity by detecting changes in blood oxygenation, providing detailed spatial maps of which brain regions are engag.
Key Functions
A nuclear imaging technique that detects gamma rays from positron-emitting radioactive tracers to measure brain metabolism, blood flow, or neurotransmitter activity, providing molecular-level information about brain function.
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 et al. (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.
Disorders
- Alzheimer's disease (amyloid PET) — A progressive neurodegenerative disease characterized by memory loss, cognitive decline, and personality changes — the most common cause of dementia in older adults.
- Parkinson's disease (dopamine transporter imaging) — Dopamine depletion causing motor symptoms (tremor, rigidity, bradykinesia) plus cognitive deficits in executive function, attention, and visuospatial skills.
- Epilepsy (interictal hypometabolism) — A neurological condition characterized by recurrent unprovoked seizures due to abnormal excessive neural synchronization, particularly in relation to interictal hypometabolism.
- Brain tumors
- Depression — Mood disorder with pervasive sadness and anhedonia; cognitive symptoms include difficulty concentrating, memory problems, and negative cognitive biases.