9 - Studying The Brain Flashcards
What are the methods to study the brain?
Post mortems
fMRIs
EEGs
Event related potentials
Outline how post mortems work
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 cortex of patients with depression.
Evaluate the use of post mortems in studying the brain
+ More detailed examination of anatomical and neurochemical aspects of the brain than would be possible with other methods of studying the brain. Enabled researchers to examine deeper regions, such as the hippocampus and hypothalamus.
- Studies using post-mortems may lack validity due to small sample size (as special permission needs to be granted) and 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, drug treatments, can all affect the brain.
Outline the use of fMRIs in studying the brain
Uses magnetic fields and radio waves to monitor blood flow in the brain.
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.
Evaluate the use of fMRIs
+ Captures dynamic brain activity as opposed to an MRI/post-mortem examination which purely show the physiology of the brain.
- Interpretation of fMRI is complex and is affected by temporal resolution, 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
Outline how EEGs work
Measures general electrical activity in the brain, usually linked to states such as sleep and arousal.
Electrodes placed on scalp - detect neuronal activity directly below where they are placed.
Electrical signals from different electrodes graphed over a period of time - 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.
Evaluate the use of EEGs
+ Useful in clinical diagnosis e.g. can record neural activity associated with epilepsy so doctors can confirm the person is experiencing seizures. Cheaper than fMRI so can be used more widely in research.
- Poor spatial resolution.
Outline how event related potentials are used to study the brain
Electrodes placed on the scalp - detect neuronal activity (directly below where they are placed) in response to a stimulus introduced by the researchers.
Event- related potentials difficult to pick out from 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.
Extraneous neural activity not related to specific stimulus will not occur consistently - activity linked to the stimulus will.
Define and describe the two different types of ERPs
Sensory ERPs - waves generated in first 100 milliseconds after a stimulus is presented. Reflect the initial response to physical characteristics of the stimulus.
Cognitive ERPs - waves generated after first 100 milliseconds reflect manner in which subject evaluates stimulus. Demonstrate information processing.
Evaluate the use of ERPs
+ Measures 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.
- 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.
