ways of investigating the brain Flashcards
functional magnetic resonance imaging (fMRI)
Used to measure changes in brain activity while a task is being performed.
• Measures changes in blood flow.
• When a task is being carried out specific areas of the brain become more active.
• Increased activity = increased need for oxygen.
• Blood flow is increased as oxygen is delivered in red blood cells.
• This change in blood flow allows researchers to map which areas of the brain are involved in a particular mental activity.
Electroencephalorgram (EEG)
Used to measure electrical activity in the brain.
-Electrodes placed on scalp can detect electrical activity in brain cells.
• When graphed over a period of time it produces an EEG (see right).
• Can be used to detect and diagnose various disorders that affect brain activity.
• Epilepsy & Alzheimers.
• Alpha | Beta | Delta | Theta | Gamma Waves
event-related potentials
Very small voltage changes in the brain triggered by specific events.
-Quite difficult to pick out amongst all the other activity.
• Stimulus is presented many times in order to establish a response.
• These responses are then averaged together.
• Extraneous neural activity won’t occur consistently and will be “canceled out”
An electrical response to a specific stimulus.
post-mortem examinations
The examination of a brain (body) after the person has died.
• Used to establish underlying causes of a particular behaviour that was displayed whilst alive.
• Researchers look for brain abnormalities that are not present in control groups to explain atypical behaviour.
• Lots of examples that have provided us with important knowledge.
• 1860s - Broca found lesions in an area of Tan’s left frontal lobe (Broca’s area)
• Annese et al. (2014) found lesions in HM’s hippocampus explaining the inability to store new memories.
° Reduced amounts of glial cells in people with depression. (Cotter et al., 2011).
strength fMRIs
• Unlike other scanning techniques such as PET scans, it does not rely on the use of radiation.
-It has very good spatial resolution. This means that it produces images that depict detail by the millimetre, making it possible to get a clear picture of how activity is localised in the brain.
limitation fMRI
MRIs can only measure blood flow, it cannot home in on the activity of individual neurons and so it can be difficult to tell exactly what kind of activity is being shown on the screen. This means it is not a truly quantitative measure of mental activity in these areas of the brain.
strength EEGs
EEGs are useful in clinical diagnoses.
• Record the abnormal neural activity associated with epileptic seizures. This can help to determine whether someone experiencing a seizure has epilepsy.
limitation EEGs
• Poor spatial resolution. EEGs only provide very generalised information. Electrical activity can be picked up by several neighbouring electrodes, which makes the source of any activity difficult to pinpoint.
• Researchers can’t distinguish between activities originating in different but neighbouring locations in the brain.
strength ERPs
• Provides increased specificity to the measurement of neural processes compared to
EEGS.
Excellent temporal resolution, as ERPs are derived from EEGS
• Led to their widespread use in the measurement of cognitive functions and deficits.
limitation ERPs
ERPs are very small and often difficult to pick out from other electrical activity in the brain.
° This means that a large number of trials often have to be conducted in order to gain meaningful data.
• Limits the types of questions that ERP readings can realistically answer.
strength post mortems
• Post-mortems allow for a more detailed examination of anatomical and neurochemical elements of the brain, which would not be possible with less invasive methods such as fMRis and EEGs.
• Have deepened our understanding of certain disorders such as schizophrenia.
• Structural anomalies and evidence of changes to neurotransmitter systems, which are both associated with the disorder (Harrison, 2000).
limitation post mortems
People die in a variety of circumstances and at varying stages of disease, both of which can influence the post-mortem brain.
• Drugs treatments, age at death and time between death and PM are possible confounding variables. This means that the observed damage to the brain may not be linked or may paint an incorrect picture of the behaviour under review.
