Ways of Studying the Brain

Created by

Cards (43)

Functional magnetic resonance imaging (fMRI):
fMRI is a non-invasive way of studying the brain that works by detecting the changes in blood flow that occur because of brain activity in specific parts of the brain
when a brain is more active it consumes more oxygen and to meet this increased demand blood flow is directed to the active area
for example, Maguire's taxi driver study used fMRIs to scan the brains of her taxi-drivers and non-taxi drivers when doing memory tasks. They found that the hippocampi of taxi-drivers were significantly larger than non-taxi drivers
Process of fMRI scans:
the participant/patient lies in the scanner, ensuring they have no metal or electronics on their person (including pacemakers or pins for injuries like broken ankles) as the machine uses extremely strong magnets
when haemoglobin in the blood has oxygen, it reacts differently to magnetic stimulation compared to when it doesn't have oxygen
the scanners then use a magnet to measure the amount of haemoglobin that is being used by different parts of the brain
Process of fMRI scans:
4. when the brain is active it is using more oxygen and glucose and the fMRI can detect where the haemoglobin in the blood is oxygenated and where it is not
5. the fMRI produces a 3D image (called an activation map) which shows which parts of the brain are active when doing different mental processes. This is important for helping us understand localisation of function
6. it does this within 1-4 seconds (low temporal resolution)
7. finally, it detects this activity with a precision of 1-2 mm (high spatial resolution)
Evaluation of fMRI scans:
S - high spatial resolution
S - low temporal resolution
High spatial resolution (identify):
a strength of fMRIs is that they have high spatial resolution
High spatial resolution (explain):
spatial resolution is the extent to which the scanner provides a detailed image of the brain. The activation map produced by an fMRI is highly accurate (1-2mm)
this is a significantly more detailed image than any other brain imaging technique
for instance, the Maguire study decided to use fMRI over other imaging techniques as it produces a much more detailed image of the participant's hippocampi
High spatial resolution (conclusion):
this shows the importance of high spatial resolution in localisation research because, it can show us precisely where in the brain is active during tasks or the size of different localised regions
Maguire's study used fMRI because she needed the high level of detail in her hippocampus scans
Low temporal resolution (identify):
a weakness of fMRIs is that they have a low temporal resolution
Low temporal resolution (explain):
temporal resolution refers to the accuracy of the scanner in terms of how long it takes between the brain activity and the measurement being taken
fMRI relies on measuring brain activity indirectly via blood flow and so the temporal resolution is low (with a 3 second delay), meaning it can be hard to determine a cause and effect relationship at times
when a study requires immediate measurements of brain activity then EEG or ERP equipment is much better
Low temporal resolution (conclusion):
this is important because it means we might not see brain activity in real time meaning conclusions, that are drawn about brain activity are not measuring what they aim to measure as it is measuring what happened 3 seconds ago
Electroencephalograms (EEGs):
EEGs are a non-invasive way of measuring the electrical activity of the brain by placing electrodes that are fixed to a person's scalp using a skull cap
information is processed in the brain as electrical activity in the form of action potentials or nerve impulses (neurons firing)
the EEG detects very small changes in electrical activity in the brain, which are picked up by the electrodes
this activity is digitally graphed over a certain time indicating the level of activity. The image is shown on a computer screen
Electroencephalograms (EEGs):
the scan shows brainwave patterns that result from the action of millions of neurons. They are used to record general brain activity linked to states such as sleep and arousal
for example, a study on French cave explorer Michel Siffre's who lived isolated in a cave for 6 months used EEGs at night to measure brainwave patterns during his sleep
Evaluations of EEGs:
S - high temporal resolution
W - low spatial resolution
High temporal resolution (identify):
a strength of EEGs is that they have high temporal resolution
High temporal resolution (explain):
temporal resolution refers to the accuracy of the scanner in terms of how long it takes between the brain activity and the measurement being taken
as this method measures brain activity via electrical impulses it means it picks up brain activity within milliseconds which is almost in real time
this was particularly useful in the Siffre cave study on sleep as it means that they could see precisely how his sleep pattern had changed when living in the cave
High temporal resolution (conclusion):
this is important because it shows us brain activity in real time, meaning we can determines cause and effect between what is happening in the environment and what is happening in terms of brain activity
Low spatial resolution (identify):
a weakness of EEGs is that they have low spatial resolution
Low spatial resolution (explain):
spatial resolution is the extent to which the scanner provides a detailed image of the brain
EEGs have low spatial resolution of only generic and superficial brain areas, meaning it could tell you the lobe, but maybe not the exact cortex where the activity is happening
they are not suitable for any research on localisation of the brain as they don't give a detailed image of the brain
Low spatial resolution (conclusion):
this is important because it means that the method is not useful when doing localisation studies
research that is looking into brain localisation could not be done with an EEG as it just shows us general activity of the brain and not localised areas
Event-related potentials (ERPs):
ERPs use the same equipment as EEGs and also measure the electrical activity of the brain
the difference is that they record activity in response to a specific stimulus, such as a story, picture or sound and then their brain activity would be measured
researchers are able to isolate the brain activity that corresponds to that particular stimulus using a statistical averaging technique that filters out all the extraneous brain activity
this works by presenting the stimulus several hundred times and a computer then cancels out the background brain activity and just presents the event-related potential
ERP example:
for example, a study by Benjamin Libet hooked participants up to an ERP and measured the participants' brain activity of the motor regions when they decided to move their finger
they found that the ERP showed brain activity was happening before they had consciously decided to move their finger
Evaluation of ERPs:
S - high temporal resolution
W - low spatial resolution
High temporal resolution (identify):
a strength of ERPs is that they have a high temporal resolution
High temporal resolution (explain):
temporal resolution refers to the accuracy of the scanner in terms of how long it taken between the brain activity and the measurement being taken
as this method measures brain activity via electrical impulses it means it picks up brain activity within milliseconds, which is almost in real time
this was particulate used in the Libet study on free will and determinism as it could tell us precisely when the brain activity occurred and whether it was before their conscious decision to move their fingers
High temporal resolution (conclusion):
this is important because we can see precisely when there is brain activity in that particular region
in the Libet study, the ERP was able to distinguish between the brain activity and the finger movement which was a matter of milliseconds
Low spatial resolution (identify):
a weakness of ERPs is that they have low spatial resolution
Low spatial resolution (explain):
spatial resolution is how precisely the method shows us an image of the actual brain activity
ERPs have a low spatial resolution of only generic and superficial brain areas, meaning it could tell you the lobe, but maybe not the exact cortex where the activity is happening
they are not suitable for any research on localisation of the brain as they don't give a detailed image of the brain
Low spatial resolution (conclusion):
this is important because it means they won't be used on localisation research where an fMRI may give a clearer image about what is happening in the brain
the ERP will just suggest a region where the brain activity is occuring
Post-mortems:
this is when a person's brain is analysed after death. These are usually done on people who have had psychological/developmental disorders or problems with certain mental processes and behaviours when they were alive
the purpose of this is not for psychologists to determine the cause of death, but instead, researchers would look at areas of damage in the brain to establish the cause of any problems that they had when they were alive. These brains are also compared to neurotypical 'healthy' brains to see how they differ
Post-mortems:
the physical examination of the brain looks for 2 main characteristics of the brain;
anatomical structure (physical make-up of the brain)
the neurochemistry (the amount and concentration of neurotransmitters)
this is a retrospective examination, making casual relationships is tricky and is not unethical, due to the patient being deceased there is no psychological or physical harm and the family will have provided consent for the body to e donated to science
Post-mortem example:
for example, H.M. was a case study who underwent a post-mortem
when he was alive he had surgery to remove his hippocampus (to treat his epilepsy), which resulted in him being unable to form new memories
the post-mortem allowed researchers to get greater detail of the damage caused by the surgery
Evaluation of post-mortems:
S - high level of detail
W - post-mortems don't show brain activity
H.M case study:
in the H.M case study researchers were given access to his brain after his death and used hi-tech equipment to create millions of slices of his brain which could then be photographed in great detail (to the individual neuronal level)
High level of detail (identify):
a strength of post-mortem examinations is that they provide a higher level of detail than non-invasive techniques like fMRI or EEG
High level of detail (explain):
if the brain is carefully removed then this means the brain can be examined with a high level of detail
for example, in the H.M case study researchers were given access to his brain after death and used hi-tech equipment to create millions of slices of his brain which could then be photographed in great detail (to the individual neuronal level)
High level of detail (conclusion):
this is important because it means we can see in great detail the damage to the areas of his brain
we can then use this to infer the function of the damaged region, suggesting that hippocampus damage causes problems forming long-term memories
Doesn't show brain activity (identify):
a weakness of post-mortems is that they don't show brain function
Doesn't show brain activity (explain):
as the brain is no longer alive it means that any conclusions we make about the brain and it's influence on behaviour will be retrospective
this means it's difficult to infer cause and effect between the damaged areas of the brain and their behaviour in real life
for example, we can only infer that the lack of a hippocampus is what caused H.M's memory loss
Doesn't show brain activity (conclusions):
this is important because it means the conclusions drawn from post-mortems may lack validity
H.M for instance may have had bad memory loss because of another reason other than his hippocampus damage
an fMRI scan whilst he was alive would have shown actual activity (or inactivity) during memory tasks
Spatial resolution:
refers to the smallest feature (or measurement) that a scanner can detect and is an important feature of brain scanning techniques