LP 2: Brain imaging techniques
The following lesson plan is an introduction to brain imaging techniques - a key way in which psychologists are able to study the brain.
Although I will focus on MRIs (structural) and fMRIs (functional) as techniques, I will also show them what else is happening in the world of neuroimaging. This lesson does not focus on specific studies as we have already discussed Maguire and Sharot in the previous lessons. Students will be exposed to further research throughout the course.
Presentation on neuroimaging techniques
Discussing brain imaging
Watch the following video. What does Daniel Amen say that we have learned from brain scanning technology?
How an fMRI works
You may want to also show the the following video with Alan Alda which has a fairly good explanation of how the fMRI works.
Evaluating brain imaging techniques
Now, go over the homework reading. Here are some of the key points:
1. The environment is unnatural and may influence the outcome of the research.
Poldrack (2008) argues that up to 20% of subjects are affected by claustrophobia and refuse to take part in research in an MRI or fMRI. In addition, obese participants are excluded. This may, in some cases, lead to sampling bias. In order to make sure that the participant lies still in the MRI, the tasks which they may be asked to do are very limited and mostly artificial in nature.
2. Colours exaggerate the effects of the brain.
The colors are often misleading, making it look like a specific region of the brain is clearly defined when in fact the activity of the brain is much more distributed and not as localized as we would like to believe. In addition, a lot of activity in the brain is spontaneous and not stimulus driven. We often cannot be sure why there is activity in a part of the brain or what it is doing. Brain areas activate for many different reasons.
3. Brain images are compilations.
The final image is a statistical compilation of several images taken over the duration of the scan. It is not an image of the brain at any specific time.
4 Scanning is more ethical and more practical than past data gathering techniques.
In spite of the limitations listed above, brain scanning has been a major help to our understanding of how the brain works, as well as helping to diagnose people with everything from Alzheimer's to schizophrenia. Research is much more ethical than the early research as the techniques are non-invasive. In addition, they are incredibly practical. A team of researchers around the world can easily discuss an MRI scan by sending it as an email attachment! This allows for researcher triangulation in the analysis of the data and may lead to a higher validity of the conclusions reached.
After watching the slide show, the videos and reading the homework, have students outline the strengths and limitations of an MRI and an fMRI. Here are some potential answers.
Strengths and limitations of MRI and fMRI Scans
- MRIs are non-invasive, unlike the PET scan.
- Less expensive than PET and better temporal resolution. This means that the image is taken several times and then made into a composite image. This composite image is often lacking in precision and clarity, but is better than the PET scan.
- The MRI is a static image that does not demonstrate activity. Research is therefore correlational. Causation cannot be established.
- Although cheaper and safer than PET scans, the MRIs are still expensive. This means that sample size for research studies is often small. This makes it difficult to generalize the findings.
- Researchers can carry out limited experiments in an fMRI which allow for cause and effect relationships to be established.
- The fMRI is an artificial environment which means that experiments carried out in the fMRI lack ecological validity. As the MRI is only taking a picture of the static brain, ecological validity is not a concern.
- Artefacts can affect the "findings" of a brain scan. Artefacts can be activity in the brain as a result of something else besides what it being investigated - e.g. anxiety about being in the fMRI. It can also be from the machine itself, see the study by Bennett et al, 2010.
- Allows for researcher triangulation.
- When used for research, there is the ethical problem of informed consent. Researchers may find a tumour or some other abnormality; it would be required for the researcher to inform the participant about any such findings.
Questions for discussion
The folllowing questions are areas for further discussion.
- Discuss ethical concerns about studying the brain. How have ethical practices improved over the past fifty years?
- Choose a topic in psychology: crime, memory, relationships, addiction, arousal in sport. Think of an example where you would use a structural MRI and when you would use an fMRI.
Trevor Mrak posted this great Ted Talk which not only discusses technology, but also the question of localization of function. Definitely worth watching.