Studying the Brain Flashcards
What are fMRI scans?
- 3D scans providing structural and functional information,
- they show changes in brain activity as they actually happen, by using strong magnetic field and radio waves.
How do fMRI scans work?
1) Rely on the haemodynamic response, more oxygenated blood flows to active areas of the brain,
2) Molecules in oxygenated blood respond differently to a magnetic field than those in deoxygenated blood,
3) The more active areas of the brain can be identified.
What are the uses of fMRI scans?
1) used to research the function of the brain as well as its structure,
2) Can be used to diagnose medical problems; they can show damaged or diseased parts of the brain,
3) Also used to study abnormal activity in the brain.
Advantages of fMRI?
- High spatial resolution - as up to 4 images can be produced per second,
- Can be used whilst a patient is carrying out a task, and so data from fMRI scans can help us to make inferences about brain function and localisation,
- Does not use ionising radiation, unlike PET scans; is safer.
Limitations of fMRI scans?
- Poor temporal resolution because there is approximately a 5 second difference between neuronal activity and the produced image.
What are EEGs? how do they work?
- Electroencephalograms show overall electrical activity of the brain, picks up on the signal of many neurons firing together,
- Multiple electrodes are placed on the scalp and the electrical activity in the brain is recorded for a period of time,
- This produces a pattern of waves; patterns represent different levels of arousal or consciousness.
What are the uses of EEGs?
1) Commonly used in sleep studies,
2) Been used in the study of conditions such as depression and schizophrenia,
3) Abnormal EEGs have also been identified in patients suffering from eating disorders,
4) EEGs have the potential to be used as a diagnostic tool.
Advantages of EEG scans?
- Particularly useful in investigating the characteristics of the different stages of sleep, as demonstrated by Dement and Kleitman,
- Much higher temporal resolution than fMRI scans, and so more appropriate for the monitoring of ongoing cerebral states and activity,
- Useful in the diagnosis of epilepsy, which is characterised by random bursts of activity.
Limitations of EEG scans?
- Lower spatial resolution compared to fMRI scans - have particular difficulty in differentiating activity between adjacent areas.
What are ERPs?
- Brain’s electrophysiological responses to specific events (sensory, motor, or cognitive event) are isolated by doing a stastical analysis of EEG data,
- The statistical averaging technique removes all extraneous brain activity from the original EEG recording by filtering it out leaving only those responses that relate to the presentation of a specific stimulus or performance of a specific task,
- What is left is event-related potentials - brainwaves that are triggered by particular events,
- Different types of ERP have been discovered, e.g. linked to attention, perception.
Advantages of ERP study?
- Excellent temporal resolution - Neural processes are measured more specifically than in an EEG,
- Widely used in the measurement of cognitive deficits and functions.
Limitations of ERP study?
- Lack of standardisation in ERP methodology in different research studies,
- Background noise and extraneous material can be an obstacle.
What are post-mortem examinations?
- Dissections of the brain of a person who has died,
- Allows researchers to physically look at the internal structure of the brain.
Advantages of post-mortem examinations?
- Particularly useful for advancing medical knowledge. Being the basis of further research into certain areas of the brain, e.g. Broca used a post-mortem examination on his patient Tan leading to the identification of Broca’s area and was the foundation of further research into the theory of localisation of brain function.
Limitations of post-mortem examinations?
- Incorrectly makes the assumption that differences compared with the neurotypical brain must be the explanation for neurological or cognitive deficits. Prolonged drug use, stress, and genetic factors may be other plausible explanations,
- Ethical issues arise because informed consent cannot always be obtained before the patients dies or from the family. The patient may be unable to give informed consent, e.g. HM suffered from deficits in his short-term memory, and so would not have remembered signing the document.
