Magnetic Resonance Imaging (MRI)
Magnetic Resonance Imaging (MRI)
MRI uses a powerful magnetic field and radio waves and magnetic fields to detect energy emitted by hydrogen atoms in the brain, which vary depending on the type of tissue. This creates a detailed, static three-dimensional image of brain structure.
Procedure
- Participants lie on a table that slides into a cylindrical scanner. The machine generates images based on the varying hydrogen concentrations across different brain regions.
Strengths
- Non-invasive and safe, with no radiation exposure.
- Provides high spatial resolution, allowing for detailed imaging of brain structure.
Limitations
- Does not provide information on brain activity.
- The procedure can cause anxiety in claustrophobic participants.
- Expensive and unsuitable for individuals with metal implants.
Maguire et al. (2000) investigated the brain structure of London taxi drivers and found increased grey matter in the hippocampus, which is associated with their advanced navigational skills. This study used MRI to identify structural differences in the brain.
Functional Magnetic Resonance Imaging (fMRI)
Functional Magnetic Resonance Imaging (fMRI)
fMRI detects changes in blood oxygenation levels (BOLD signal) to identify active brain regions during specific tasks. Active areas receive more oxygenated blood, thus it is responsive to the brain's metabolism. The result is a time map, showing when certain parts of the brain were activated.
Procedure
- Participants perform cognitive tasks (e.g., viewing images or solving problems) while lying in the scanner. The machine captures changes in brain activity related to the task.
Strengths
- Combines structural and functional imaging, showing active brain regions.
- Excellent spatial resolution compared to other functional techniques.
Limitations
- Temporal resolution of about 1 second limits the detection of fast processes.
- Noise from random thoughts or movements can affect data accuracy.
- Expensive and time-intensive.
Passamonti et al. (2012) explored the impact of serotonin on the amygdala and prefrontal cortex (PFC) during the perception of social threats. The researchers utilized fMRI to examine brain activity under different serotonin conditions.
Radke et al. (2015) examined the role of testosterone in amygdala activation when participants approached threatening faces. fMRI was employed to measure how testosterone influenced brain activity during this task.
Positron Emission Tomography (PET)
Positron Emission Tomography (PET)
PET uses a radioactive tracer binds to specific molecules (e.g., glucose) in the bloodstream. Active brain areas emit higher levels of energy, indicating increased activity.
Procedure
- Participants receive a mild radioactive glucose injection and perform tasks inside a scanner. The energy emissions highlight active brain areas.
Strengths
- Shows both brain structure and function.
- Useful for studying slow processes and neurotransmitter activity.
- Useful for monitoring blood flow while participants perform cognitive tasks.
Limitations
- Exposure to low levels of radiation.
- Poor temporal resolution compared to fMRI.
- If someone is diabetic and/or ate before the scan, results may be misleading.
Freed et al. (2001) investigated the role of dopamine in alleviating symptoms of Parkinson’s disease. The study used PET scans to observe the effects of dopamine on brain function and symptom improvement in participants.
Electroencephalography (EEG)
Electroencephalography (EEG)
EEG measures electrical activity generated by large groups of neurons. Electrodes on the scalp detect these signals, providing real-time data on brain wave patterns.
Procedure
- Participants wear a cap with electrodes while remaining still. Changes in brain wave activity are recorded during tasks or resting states.
Strengths
- Exceptional temporal resolution, detecting millisecond-level changes.
- Non-invasive, mobile, and relatively inexpensive.
Limitations
- Poor spatial resolution; cannot pinpoint exact brain areas.
- Signals from deep brain regions are undetectable.
Comparative Overview of Techniques
| Technique | Focus | Spatial Resolution | Temporal Resolution | Key Strength | Key Limitation |
|---|---|---|---|---|---|
| MRI | Structure | Up to 1–2 mm | Not applicable | Detailed imaging of brain structure | Cannot measure brain activity |
| fMRI | Structure + Process | Up to 1–2 mm | ~1 second | Shows patterns of brain activation | Noise and cost |
| PET | Process | ~4 mm | ~30–40 seconds | Tracks specific neurotransmitter activity | Radiation exposure |
| EEG | Process | Poor | Milliseconds | Exceptional for real-time monitoring | Limited to cortical activity |
- Distinguish between an fMRI and an MRI.
- What are strengths and limitations of an EEG?
