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Psychology
Methods of Brain Imaging
fMRI, EEG, PET, and MEG
Related Worksheets
Brain imaging methods let psychologists and neuroscientists study the living brain without surgery. Different tools reveal different kinds of information, such as structure, blood flow, electrical activity, magnetic fields, or chemical activity. These methods matter because they connect mental processes like attention, memory, emotion, and decision making to activity in specific brain systems. No single method is best for every question, so researchers choose a method based on what they need to measure.
Key Facts
- fMRI measures changes in blood oxygenation, called the BOLD signal, as an indirect sign of neural activity.
- EEG records electrical activity from the scalp and has excellent temporal resolution, often on the millisecond scale.
- PET uses radioactive tracers to map metabolism, receptor activity, or blood flow in the brain.
- MEG measures tiny magnetic fields produced by neural electrical currents and has very high temporal resolution.
- Structural MRI shows soft tissue anatomy in detail, while CT uses X-rays and is faster but usually less detailed for soft brain tissue.
- Spatial resolution describes where activity occurs, while temporal resolution describes when activity occurs.
Vocabulary
- fMRI
- Functional magnetic resonance imaging is a method that estimates brain activity by measuring changes in oxygenated blood flow.
- EEG
- Electroencephalography is a method that records the brain's electrical signals using electrodes placed on the scalp.
- PET
- Positron emission tomography is an imaging method that uses radioactive tracers to show brain metabolism, blood flow, or receptor activity.
- MEG
- Magnetoencephalography is a method that detects magnetic fields produced by neural electrical activity.
- Resolution
- Resolution describes how precisely a method can locate brain activity in space or track it over time.
Common Mistakes to Avoid
- Assuming fMRI directly measures neuron firing. fMRI measures blood oxygen changes, so it is an indirect and delayed signal of neural activity.
- Choosing EEG when exact brain location is the main goal. EEG is excellent for timing, but scalp signals are harder to localize precisely inside the brain.
- Treating structural MRI and fMRI as the same method. Structural MRI shows anatomy, while fMRI estimates changing activity during tasks or rest.
- Ignoring the spatial versus temporal resolution tradeoff. A method with great timing, such as EEG, may have weaker location accuracy than a method such as fMRI.
Practice Questions
- 1 An EEG study samples brain activity every 2 milliseconds. How many samples are recorded in 1 second?
- 2 A PET tracer has a half-life of 20 minutes. If the starting activity is 80 units, how many units remain after 60 minutes?
- 3 A researcher wants to study the exact timing of brain responses during a word-recognition task, while another researcher wants to identify which small brain region is most active during memory retrieval. Which imaging method would you recommend for each researcher, and why?