tools for examining brain structure and function

what is a electroencephalogram (EEG)?

a test that measures electrical activity in the brain

• electrodes placed in specific locations around the skull detect changes in electrical activity and display them visually

strengths of EEG?

non-invasive, useful for broad based behaviours like sleeping (REM patterns)

weaknesses of EEG?

inaccurate, cannot narrow down brain activity to a specific region of the brain

what is computed tomography (CT)?

A combined computer and X ray image showing slices of the skull from multiple angles including the soft tissues of the brain

what is a MRI?

a medical imaging technique that uses radio waves and strong magnetic fields to create detailed pictures of the inside of the body

weaknesses of CT?

does not show brain activity

what is a functional MRI (fMRI)?

a noninvasive brain scan that measures brain activity by tracking changes in blood flow

• the fMRI can track these changes in the brain metabolism as they occur in patients as thoughts, emotions, or actions occur

strengths of fMRI?

this enables psychologists to map the functioning regions of the brain with a high degree of accuracy

weaknesses of fMRI?

biocorrelation

strengths of MRI?

can produce a detailed three dimensional image

weaknesses of MRI?

dangerous for certain individuals – pacemakers, metal implants

Positron Emission Tomography – PET scans

an imaging system that relies on the principle that the brain’s consumption of sugars increases in areas that are active

radioactive sugars are injected into a patient that will emit gamma rays when metabolized by the brain

these rays can be detected and an image can be produced that shows localized brain activity

strengths of PET scans?

gives a colorful and dynamic picture of brain activity; shows structural changes that indicate problems before they can show up on MRI or CT scans

weaknesses of PET scans?

not as precise as a fMRI; health problems can occur with the injection of radioactive substances

lesion studies

Removal or damage of regions of the brain and studying corresponding behaviour changes under controlled conditions

• Can be done experimentally or via case study on pre-existing subjects

strengths of lesion studies?

strong correlation and clear observational variables

weaknesses of lesion studies?

ethical issues, sampling issues (humans), generalization issues (animals), biocorrelation

autopsy

Examination of a deceased individual’s body

strengths of autopsies?

provides valuable research data for hereditary diseases and information to next of kin

weaknesses of autopsies?

selection errors, biocorrelation, participant history