2.7 Discuss the use of brain-imaging technologies in investigating the relationship between biological factors and behaviour.

2.7 Discuss the use of brain-imaging technologies in investigating the relationship between biological factors and behaviour.

Brain-imaging techniques are used in neuroscience to investigate the relationship between behaviour and brain structures, for example after brain damage or to find out which areas of the brain are involved in which cognitive activities (cognitive neuroscience). Brain-imaging technology s a promising way to investigate the possible relationship between biological factors and behaviour, but so far scanning can merely register structures and activity in the brain. It is not possible to determine cause-effect relationships at this point.

MRI scan: magnetic resonance imaging

MRI scans can give detailed pictures of internal structures in the body. The body consists, to a large extent, of water molecules. In the MRI scanner, a radio frequency transmitter is turned on and it produces an electromagnetic field.

Strengths:

• MRI scans are particularly useful to show how the blood flows in the brain and can be used to identify problems with blood circulation. They can be used for the early detection of Alzheimer's’ disease.
• They are safe to use since no radioactive material is used.

Limitations:

• They are very expensive.
• Movement may affect the pictures.
• They cannot say anything about cause-effect relationships.

Ashtari et al (2009)

They used MRI to investigate whether substance abuse (marijuana) can damage the developing brain in adolescents and young adults. The researchers scanned the brains of 14 young men with a history of heavy marijuana abuse over a long period. The control group consisted of 14 young men who had not used marijuana. The results of the scan indicated that there were brain abnormalities in the frontal, parietal and temporal regions of the brains of the marijuana users. The development of white matter (myelin) was affected and this could explain slow information processing in the brain. The researchers concluded that early marijuana use can affect brain development negatively but since the study gave correlational data, more research is needed.

fMRI: functional magnetic resonance imaging

The fMRI scanner measures changes in blood flow in the active brain. This is associated with use of oxygen and linked to neural activity during information processing. When participants are asked to perform a task, the scientists can observe the part of the brain that corresponds to that function. fMRI scanning is widely used by cognitive neuroscientists and other researchers and its use has increased enormously over the last 10 years.

Strengths:

• It does not use radioactive substances.
• It can record activity in all regions of the brain.

Limitations:

• The focus is mostly on localized functioning in the brain and does not take into account the distributed nature of processing in neural networks.
• The results are correlational so it is not possible to establish cause-effect relationships.

Harris and Fiske (2006)

They used fMRI scans to study students’ brain processes as a response to being presented with pictures of extreme outgroups. This study in social cognition aimed to find the biological correlates of stereotypes and prejudice. The researchers scanned students while they were watching either pictures of different humans or objects. It was predicted that the medial prefrontal cortex would be active when participants looked at humans but not when they looked at objects. This was found except when participants looked at pictures of people from extreme outgroups such as the homeless and addicts. Brain regions related to ‘disgust’ were activated and there was no activity in the prefrontal cortex. The researchers concluded that this indicated a dehumanization of the outgroups. These groups were apparently viewed as ‘disgusting objects’ and not people.

General issues in brain imaging to consider in a discussion

Brain imaging is mainly about mapping brain structures and activity in the brain. Another limitation deals localization of function. It may be possible to identify brain structures that are active during a task but, since most structures are linked to other structures in networks, it is not possible at this point to say definitely where things happen in the brain.