Psychology - Biological approach - Methodology

Methodology

1. Brain scanning

The biological approach assumes that behaviour can be explained in terms of activity in the brain and nervous system. Therefore biological psychologists seek methods that allow them to view brain activity.

EEG - In the 1950s, the only method available for studying brain activity was the electroencephalogram (EEG). Electrodes are placed on the scalp, and electrical activity in different regions of the brain can be recorded. EEG was used in a classic study by Derment and Kleitman (1957) to detect different stages of sleep. As people go to sleep, their brain waves become slower. This can be detected by an EEG machine. During a night's sleep, this pattern occasionally changes to become very fast accompanied by the eyes darting about under closed lids. This is called rapid eye movement (REM) sleep. Dement and Kleitman woke particpants up at various points during sleep and found that the particpants were much more likely to report having a dream if they were awoken during REM sleep.

The development of brain scanning techniques - In the past 30 years, much more presice methods of studying the brain have been developed.

CAT scans (computed axial tomography) - These involve taking a series of x-rays and combining them to form a comprehensive two or three dimensional picture of the area being scanned. Usually, a dye is injected into the patient as a contrast material and then he or she is placed in the cylindrical CAT scan machine that takes the pictures.

Strengths: CAT scans are useful for revealing structures in the brain such as tumours, or structural damage. The quality of the images provided by the CAT scan is much higher than that of traditional x-rays.

Weakness: CAT scans require more radiation than traditional x-rays, and the more detailed and complex the CAT scan is, the more radiation exposure the patient receives. Pregant women are unable to be scanned this way, and repeated exposure should be avoided.

MRI scans (magnetic resonance imaging) - These involve the use of a magnetic field that causes the atoms of the brain to change their alignment when the magnet is on and emit various radio signals when the magnet is turned off. A detector reads the signals and uses them to map the structure of the brain.

A classic study by Maguire et al (2000) used MRI scans to demonstrate that taxi drivers had largerhippocampi than non-taxi drivers, supporting the view that this area of the brain is important in spatial memories.

Functional MRI (fMRI) provides both anatomical and functional information by taking repeated images of the brain in action.

Strengths: MRI gives a more detailed image of the soft tissue in the brain than do CAT scans, and involves passing an extremely strong magnetic field…