Lesson 10 Studying The Brain Flashcards
4 ways of studying the brain
Post Mortem examinations
Functional magnetic resonance imaging (fMRI)
Electroencephalogram
Event related Potentials
What is Post Mortem Examinations
Psychologists may study a person who displays an interesting behaviour while they are alive. When the person dies, the psychologists look for abnormalities in the brain that might explain their behaviour. Post-mortem studies have found a link between brain abnormalities and psychiatric disorders, for instance, there is evidence of reduced glial cells in the frontal lobe of patients with depression.
Advantages of Post Mortem Examinations
+ Post-mortem studies allow for more detailed examination of anatomical and neurochemical aspects of the brain than would be possible with other methods of studying the brain. They have enabled researchers to examine deeper regions, such as the hippocampus and hypothalamus
Disadvantages of Post Mortem Examinations
- Studies using post-mortems may lack validity because people die in a variety of circumstances and at varying stages of disease. Similarly, the length of time between death and the post-mortem, and drug treatments, can all affect the brain.
- Post-Mortem studies have very small sample sizes (as special permission needs to be granted). This means the sample cannot be said to be representative of the target population and so it is problematic to generalise the findings to the wider population.
Functional Magnetic Resonance Imaging (fMRI)
Functional Magnetic Resonance Imaging (fMRI) provides an INDIRECT measure of neural activity. It uses magnetic fields and radio waves to monitor blood flow in the brain. It measures the change in the energy released by haemoglobin, reflecting activity of the brain (oxygen consumption) to give a moving picture of the brain; activity in regions of interest can be compared during a base line task and during a specific activity.
Advantages of fMRI
+ fMRIs captures dynamic brain activity as opposed to a post-mortem examination which purely show the physiology of the brain.
+ fMRIs have good spatial resolution (refers to the smallest feature that a measurement can detect).
Disadvantages of fMRI
- Interpretation of fMRI is complex and is affected by poor temporal resolution (resolution of a measurement with respect to time), biased interpretation, and by the base line task used.
- fMRI research is expensive leading to reduced sample sizes which negatively impact the validity of the research
What is Electroencephalogram
An electroencephalogram (EEG) DIRECTLY measures GENERAL neural activity in the brain, usually linked to states such as sleep and arousal. Electrodes are placed on the scalp and detect neuronal activity directly below where they are placed; differing numbers of electrodes can be used depending on focus of the research. When electrical signals from the different electrodes are graphed over a period of time, the resulting representation is called an EEG pattern. EEG patterns of patients with epilepsy show spikes of electrical activity. EEG patterns of those with brain injury show a slowing of electrical activity.
Advantage of Electroencephalogram
+ An EEG is useful in clinical diagnosis, for instance it can record the neural activity associated with epilepsy so that doctors can confirm the person is experiencing seizures.
Disadvantage of electroencephalogram
- EEGs are cheaper than an fMRI so can be used more widely in research.
- EEGs have poor spatial resolution.
What is Event- Related Potentials
Electrodes are placed on the scalp and DIRECTLY measure neural activity (below where they are placed) in response to a SPECIFIC stimulus introduced by the researcher. Event-related potentials are difficult to pick out from all the other electrical activity being generated within the brain. To establish a specific response to a target stimulus requires many presentations of this stimulus and the responses are then averaged together. Any extraneous neural activity that is not related to the specific stimulus will not occur consistently, whereas activity linked to the stimulus will.
Advantages of Event Related Potentials
+ ERPs can measure the processing of a stimulus even in the absence of a behavioural response. Therefore it is possible to measure ‘covertly’ the processing of a stimulus.
+ ERPs are cheaper than an fMRI so can be used more widely in research.
+ ERPs have good temporal resolution (unlike fMRIs).
Disadvantages of Event Related potentials
- ERPs have poor spatial resolution (unlike fMRIs).
- Only sufficiently strong voltage changes generated across the scalp are recordable. Important electrical activity occurring deeper in the brain is not recorded. The generation of ERPs tends to be restricted to the neocortex.
