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Studying the brain - Coggle Diagram
Studying the brain
Post Mortems
Evaluation
Strength - Allows more detailed examination of anatomical and neurochemical aspects than non-invasive methods.
Strength - Harrison 2000 - PMs played central part in understanding schizophrenia. As a direct result of PMs, researchers have discovered structural abnormalities and evidence of neurotransmitter system changes associated with Sz.
Limit - people die for various reasons and diseases, these factors can influence the brain. Length of time between death and post mortem, drug treatments and age are confounding influences of difference between case and control.
Limit - retrospective as already dead. Researcher cannot ask follow up questions that arise from the autopsy concerning relationships between brain abnormalities and cognitive function. Cannot measure the active brain.
Shows correlation not causation. It may be coincidence that there is a lesion on the brain. It may be a result of brain damage rather than the cause of brain damage. (e.g. caused by a stroke rather than causing the stroke.)
Conducted after death, usually to find the cause of death.
Researchers may study the physical brain of someone who displayed particular behaviour while alive that suggested brain damage.
Broca - examined brain of man with speech problems. Discovered lesion in area responsible for speech production.
Wernicke - discovered region in brain in left temporal lobe important for language comprehension and processing.
fMRIs
Evaluation
Strength - Non-invasive, does not expose the brain to potentially harmful radiation unlike other techniques.
Strength - More objective and reliable measure than verbal reports. Useful way of investigating psychological phenomena people would not be capable of providing in verbal reports.
Limit - Measures changes in blood flow, so is not direct measure of neural activity in certain brain areas. Means it is not a truly quantitative measure of mental activity in these brain areas.
Limit - Critics argue it overlooks the networked nature of brain activity as it focuses on localised brain activity. Claimed its communication among different regions that is most critical to mental function.
Has high spatial resolution but low temporal resolution with support from brain damaged patients - Raine with aggression. Although non-invasive. It is expensive and time consuming, it is unsuitable for children.
Measures changes in blood flow to brain areas to measure changes in brain activity while a person does a task.
Increased brain activity means increased demand for oxygen means increased blood flow. Changes in blood flow mean researchers can produce maps showing areas of the brain involved in particular mental activities.
EEGs
Evaluation
Strength - records brain activity in real time rather than a still image of a passive brain. Means researchers can accurately measure a particular task or activity with the brain activity associated.
Strength - Useful in clinical diagnoses e.g. epilepsy. Epileptic seizures caused by disturbed brain activity so normal EEG reading changes. This helps diagnose epilepsy over other seizure disorders.
Limit - Only detect activity in superficial regions of the brain, cannot reveal what is going on in deeper regions such as the hippocampus. Electrodes could be implanted into non-humans to achieve this but it would be unethical to do it on humans.
Limit - Electrical activity can be picked up by several neighbouring electrodes so the EEG signal isn't useful for pinpointing exact sources of activity. It doesn't allow researchers to distinguish between activities originating in different but closely adjacent locations.
Measures electrical activity in the brain through electrodes placed on the scalp which detect small electrical charges from brain activity. These signals from different electrodes are graphed and the data used to detect disorders e.g. epilepsy or Alzheimer's.
There are four basic EEG patterns. Alpha waves - awake but relaxed, rhythmical. Beta - physiologically aroused, low amplitude, fast frequency, found during REM sleep. Delta and Theta waves occur during sleep - As a person moves from light to deep sleeps, Alpha waves decrease and are replaced by lower frequency theta waves then by delta waves.
ERPs
Evaluation
Strength - Provides continuous measuring of processing in response to particular stimuli. Makes it possible to determine how processing is affected by experimental manipulation.
Strength - measures processing of stimuli even in absence of behaviour response. Can 'covertly' monitor the processing of stimulus without needing the person to respond.
Limit - Small and difficult to pick out from other electrical activity in the brain. Requires lots of trials for a sensible amount of data. Limits the questions ERPs can realistically answer.
Limit - Only sufficiently strong voltage changes are recordable. Important electrical activity deep in the brain is not recorded so the use of ERPs is restricted to the neocortex.
Stimuli trigger small voltage changes in the brain which are difficult to pick out from other electrical activity being generated. To establish a specific response to a stimulus, many presentations of the stimulus are averaged. Unrelated extraneous activity will not appear consistent whereas stimulus activity will so that it can be identified.
There are two categories of ERPs. 1) Waves occurring within first 100 milliseconds after stimulus presentation are 'sensory' ERPs as they reflect initial response to physical characteristic of stimulus. 2) Generated after first 100 milliseconds reflect how person evaluates stimulus, 'cognitive' ERPs as demonstrate information processing.