2. MRI (Magnetic Resonance Imaging)
3. fMRI (functional MRI)
The participants for this study were 16 healthy, right-handed male licensed London taxi drivers. The taxi drivers were compared with the structural MRI scans of 50 healthy right-handed males who did not drive taxis. The scans of the 50 control participants were selected from the structural MRI scan database at the same unit where the taxi drivers were scanned. The first main findings of the research were that the posterior hippocampi of taxi drivers were significantly larger relative to those of control subjects.
The scientists used fMRI to obtain “minute by minute” brain images from 20 taxi drivers as they delivered customers to destinations on “virtual jobs”.
The scientists adapted the Playstation2 game “Getaway” to bring the streets of London into the scanner.
After the scan the drivers watched a replay of their performance and reported what they had been thinking at each stage.
The hippocampus was only active when the taxi drivers initially planned their route, or if they had to completely change their destination during the course of the journey.
The scientists saw activity in a different brain region when the drivers came across an unexpected situation – for example, a blocked-off junction.
PET scans are useful in early diagnosis of Alzheimer’s disease and they provide useful images of metabolic activity and structure in the brain. Both the fMRI and the MRI show actual brain activity and indicate when certain areas of the brain are active when engaged in behaviours. FMRI have higher resolutions than PET scans and are easier to carry out. In short each of these imaging techniques provide valuable insights into the relationship between biological factors and human behavior.
Furthermore, research of this kind cannot establish a cause effect relationship. No variable was manipulated by the researchers and there was no random allocation to groups. Researchers still usually have to make inferences from any scans obtained. Brain areas activate for different reasons. We do not know for example that the changes seen in the brains of the London’s taxi drivers are not the result of stress, rather than as a result of memory. Some researchers have suggested that the use of colours may exaggerate the different activities of the brain.
Brain imaging technologies such as these are of course costly techniques in terms of expensive equipment and researchers’ time, although the use of computers does make very sophisticated analysis possible. PET scans in particular are very expensive.
The fMRI and MRI are non invasive although some people can feel uncomfortable in the tight spaces. Although PET scan is harmless, it does use small amounts of radiation which makes it slightly invasive.