biological approach- techniques to study the brain Flashcards
why scan the brain?
As a diagnostic tool to diagnose/investigate medical abnormalities e.g. cancerous tumours, dementia
to investigate unusual cognitive/behavioural activities.
to research e.g. how the brain reacts to specific stimuli etc.
how does the ablation/lesioning of tissue help investigate the brain?
the function of specific parts of the brain is tested by removing/scarring the tissue and studying any changes to behaviour.
STUDY:
Hetherington and Ranson 1942 lesioned the VHM in rats. They ate double their usual intake. Conclusion: VHM acts as a brake on eating; know when you are full.
how does brain autopsy work as a technique to study the brain?
brain autopsy is the study of a brain after death, usually of someone who has demonstrated unusual behaviour while alive. Some diseases like Alzheimer’s still cant be treated until a brain autopsy is given.
how does brain surgery work as a technique to study the brain?
brain surgery is the physical exploration of the brain while the patient is still alive. It is usually used when a scan does not show clear enough results, e.g. to determine the boundaries of a brain tumour
what is an MRI scan?
A magnetic resonance scan uses magnetic fields and radio waves to create a 3D image of the brain. It detects the hydrogen protons in the water molecules in the brain tissue to map out a structure. This creates a composite image of the brain which can be viewed from various angles, either as the entire brain or as small sections.
what can an mri scan detect?
can be used to investigate how the structure of the brain changes in certain circumstances, or to test for brain tumours, bleeding, damage from injury, infection, or stroke.
how can you analyse an mri scan?
voxel-based morphometry measures difference in density of structures withing the brain, while pixel counting calculates the area/volume of an area of a brain.
what are the positives of an mri scan?
produces very detailed 3d images which can be used for research or to diagnose medical issues e.g. brain tumour. Does not use highly ionising EM waves so is relatively safe to use, especially in cases which need frequent scans.
What are the negatives of an mri scan?
not suitable for all- e.g. noisy and must stay still for 30-60 minutes so not suitable for children/those with claustrophobia. Uses strong magnetic fields so not suitable for those who have previously been given metal inserts.
Very expensive in comparison to other scans- not all hospitals/countries may be able to afford it in every case other than the most severe.
what is the key study for MRI
Maguire et al (2000)
AIM- investigate if extensive use of spatial navigation changes the brain’s structure
METHOD- MRI scans were made and analysed from an experimental group consisted of 16 right-handed male taxi drivers, and a control group consisted of 50 right handed male non-taxi drivers.
RESULTS- increase in grey matter was found in brains of the taxi drivers,
Positive correlation between volume of right posterior hippocampus and time spent as a taxi driver.
CONCLUSION- evidence for structural differences between hippocampi- suggests extensive spacial navigation affects hippocampus, brain can change in response to environmental demands- spatial navigation is localised to the right posterior hippocampus.
what are the strengths and weaknesses to the Maguire et al study?
STRENGTHS- control group scans came from a pre-existing database- cut down on the cost of the study.
WEAKNESS- consent of the patients for their information to be used.
evidence gained about the taxi drivers was only correlational, rather than causational
What is an fMRI
functional magnetic resonance imaging scan.
measures the activity of the brain when tasks are performed.
Creates an image from magnetic signature of oxyhaemoglobin which clumps around active neurones as they need oxygen to respire. radiowave displaces H protons- how quickly they return to inital position= how much oxyhaemoglobin is there.
Brighter areas of image= more activity.
The image created is mapped in squares called ‘voxels,’ which represent thousands of nuerones each.
what is susan fiske’s stereotype content model (SCM?)
- Susan Fiske’s Stereotype Content Model (SCM):
- Stereotypes have two dimensions: warmth and competence
- Warmth: perceived lack of competition with in-group
- Competence: perceived high status (economic or educational success)
- SCM proposes four types of stereotyping:
- Paternalistic stereotype
- Admiration
- Contemptuous stereotype
- Envious stereotype
- Lack of competition predicts perceived warmth
- Status predicts perceived competence
what is the study for fMRI?
Harris & Fiske’s study focused on reactions to “extreme out-groups” (homeless and addicts)
METHOD-
22 Princeton University undergraduates
Two conditions: 10 viewing people images, 12 viewing object images
Participants practiced rating photos for emotions: pride, envy, pity, and disgust
In fMRI, shown six sets of ten photographs of various groups
Participants chose which emotion they felt toward each image
RESULTS-
“Objects” group showed no activity in medial prefrontal cortex
“People” images generally activated medial prefrontal cortex
Exception: Images of addicts or homeless people
* Activated amygdala
* Triggered disgust reactions
* Activated insula (usually response to non-human objects)
* Did not activate medial prefrontal cortex (associated with thinking about people)
CONCLUSION-
Brain did not react to homeless as people
Social Identity Theory (SIT) may be oversimplified
Other factors beyond in-group/out-group distinction may influence reactions
Perceptions of resource threat and out-group status may play a role in brain reactions
evaluation
STRENGHTS:
a true study
Use of fMRI eliminates demand characteristics
LIMITATIONS:
Expensive equipment leads to small sample size
Reliability needs further testing
Small sample size (10 in relevant group) limits generalizability
Potential bias: all American, Princeton University students
Possible influence of intelligence/socioeconomic status
