Over many years neurologists and psychologists have been interested in exactly what it is that causes people to behave the way they do in everyday behaviour and people with mental illnesses or brain damaged patients. With the use of a variety of different tools to identify specifically what areas of the brain is involved in different actions.
It is most common for neurologists or psychologists to assess damaged brains as it allows clinicians to contrast the impaired abilities to the intact ones, this also helps when it comes to rehabilitation as clinicians can target the intact abilities to help the patient.
Past brain assessments such as MR scans reveals that the brain is completely normal and Lesions do not show everything. PET and FMRI and NMR shows areas of activity and inactivity allowing you to assess behaviour and link to highlighted areas of the brain.
Hysterically paralysed patients where asked to attempt to move paralysed area of body even if the body can’t the PET scan then highlights in brain the active areas. Through the use of EEG researchers are able to test patients reaction time. Researchers could tell the patient to move their finger and the EEG shows that before the finger is moved the area required to move the finger is highloighted and there is a second delay before the action is executed, it has been suggested that this delay is dued to neural processing.
There are six different types of tools that are used to look at the process
Single Case Studies
This is the investigatiom of behaviour of one individual over a intensively long period of time.
Advantages
è Valuable because human brain lesions cannot be performed experimentally
è Brain damage may highlight role of damaged region in function
è Allows in-depth study over long periods of time
è Can be used to constrain theproespf cognition in a way not possible in experimental studies of healthy individuals
Disadvantages
è Invasive
è Subject to individual differences
è Locus of damage can be variable and may not always be described accurately
è Previous level of functioning may be unkown
è Other damaged brain regions may be producing deficits
è There may be confounding factors such as medication use
Electroencephalography (EEG)
This tool records electroencephalograms also known as brainwaves. The method is non invasive as brainwaves are gathered through the use of electrodes which are placed on the scalp.
Advantages
è Non-invasive
è Excellent temporal resolution
è Relatively easy and cheap to operate
è Can be used with healthy and clinical human participants
è Can be used to record brain electrical activity in real time
è Can be used to measure the brains response to a number of psychological variables
Disadvantages
è Ability to localize function is weak – generating source may be at some distance from the recording source
è Activity is recorded from millions of groups of neurons
è Signal may be attenuated and smeared
è Brain activity may fluctuate unpredictably and ‘chaotically’
è Susceptible to movement artefact
è Unclear what EEG changes signify
Event Related Potentials (ERP)
Event-related potentials (ERPs) are large slow brainwaves that appear as a result of sensory or cognitive stimulation.
Advantages
è Can be used in healthy and clinical participants
è Useful index of sensory function
è Possible measure of cognition decline and normal cognitive function
è Non-Invasive
è High temporal resolution (one millisecond)
è Relatively easy to use and measure
Disadvantages
è Significance of some waves unknown
è Mechanism underlying ERP poorly understood
è Spatial resolution relatively poor
Positron Emission Tomography (PET)
It measures brain function via the measurement of brain oxygen consumptions blood flow and glucose metabolism. Blood flow is the most reliable of those measurements
Advantages
è Can be used with most clinical and healthy subjects
è High spatial resolution
è Measure of neuronal activity (indexed by blood flow/metabolism) in vivo
è Give three- dimensional representation of regional activity
è Can be used to measure brain activity during task performance
Disadvantage
è Invasive
è Poor temporal resolution (Blood flow is slower than neural transmission)
è Cannot be used in children or premenopausal women (because of the injection of radioactive substances)
è Tasks must take longer than a minute
è Averaging does not take into account contro-anatomical variation
è Expensive
Magnetic Resonance Imagining (MRI)
Magnetic resonance imaging (MRI) is based on changes in the magnetic properties of atoms and was developed to observe the activity of atomic nuclei.
Advantages
è Non-invasive and non- toxic
è Allows structural imaging
è Provides the best spatial resolution of current imaging technique (1-2mm)
è No known biological risk
Disadvantages
è Procedure difficult if participant is claustrophobic
è Magnet precludes introduction of ferromagnetic material into testing environment
è Equipment producing radio frequencies must be shielded
è Obtaining good images from areas near to large cavities is diffuclt
è Transient scanner effects can produce one bad image out of ten or twenty
è As with PET, ensuring similar heard placement for each participant is difficult
è Noisy procedure
Functional Magnetic Resonance Imaging (FMRI)
FMRI measures blood oxygen level dependent ( BOLD) responses . It has been used to study a variety of behaviour, from language difficulties in developmental dyslexia to face recognition, to personaility and the recognition of the emotions to being in love.
Advantages
è Measures direct changes in brain tissue from normal and clinical participants
è Non invasive and non- toxic
è Allows functional imaging
è Provides the best spatial resolution of current imaging techniques (1-2mm)
è No known biological risk
è More widely available and cheaper than PET
Disadvantages
è Decrease in venous oxygen content are not observed by FMRI
è Procedure difficult if participant is claustrophobic
è Poor temporal resolution ( four images per second is the current norm)
è Magnet precludes introduction of ferromagnetic materials into testing environment
è Equipment producing radio frequencies must be shielded
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