Research Methods Flashcards
(46 cards)
Structural Brain - Phrenology
Individual differences in skull anatomy link to behaviour
Assumes that different regions have different functions for controlling different behaviours - localisation of function
Assumes that the size of distortion in proportion to the size of the region relates to the effects on cognition and personality
Structural Brain - Pathology
Studying the brain posthumously
Looking at the differences in eminent brains
Structural Brain - Pathology, Einstein
Examined brain after death
Had extremely high IQ
Missing the sub-marginal gyrus
Structural Brain - Pathology, Limitations
Biased sample due to need for donations
Cannot correlate activity in the area to abilities as a deceased brain cannot be stimulated to produce bodily responses
Structural Brain - Modern Approaches
Assume that different types of tissue have different properties and so will absorb or reflect different amounts of radiation which can then be detected and computerised to form an image
Structural Brain - Computerised Axial Tomography
Dye is injected into the body to increase contrast
X-rays are passed through the brain and unabsorbed rays are detected
Detectors use computers to form an image of the brain
White matter is dense and so will absorb lots of xray radiation - if few rays are detected, the region must have lots of white matter
Structural Brain - CAT Evaluation, Strengths
Can pick up details in large abnormalities
High contrast
Low intrusivity
Structural Brain - CAT Evaluation, Weaknesses
Poor spatial resolution ( .5 - 1 cm )
Low temporal resoultion
Radiation exposure
Possible reaction to dye
Structural Brain - Magnetic Resonance Imaging
H+ atoms orient parallel to magnetic fields
Radio waves cause H+ to move 90 degrees, resulting in a change in the magnetic field which is detected by magnets and formed into an image
H+ are protons found surrounding each atom, more dense tissue has more atoms and so more H+, more H+ atoms causes more vibrations, indicating denser tissue
Structural Brain - MRI Evaluation, Strengths
High spatial resolution ( 1 - 2 mm ) in comparison to CAT
Low intrusiveness
Structural Brain - MRI Evaluation, Weaknesses
Cannot scan those with internal metallic devices
Relatively low spatial resolution
Poor temporal resolution
Chance of claustraphobia
Structural Brain - Ultrasound / Sonogram
Passes high frequency pulses throuhg the body that are reflected back when they hit dense matter
The time take for a pulse to be reflected back (echo) is translated into distance and used to create an image
White matter is denser than grey matter so will reflect more pulses
Structural Brain - US Evaluation, Strengths
High temporal resolution ( 10 - 30 ms ) High spatial resolution Low cost No exposure to radiation Able to detect blood flow
Structural Brain - US Evaluation, Weaknesses
High amounts of tissue distort pulses so cannot be used on patients with excess fat
Pulses cannot pass through bone so the brain can only be scanned during open-skull surgery or within the first 18 months of life
Functional Brain
Assumes that neural activity produces physiological changes in the brain
Functional Brain - Electroenchephalogram
Conduction gel and an electrode cap are applied to the head of the participant, with electrodes in a 10 - 20 formation
Electrodes continuously detect neuronal electrical activity of neurons firing together, measuring the oscillations and frequencies of brain waves
Differences between electrodes are used to calculate relative activity
Computer will filter artefacts and average the waves to produce Event-Related Potentials
Functional Brain - EEG Evaluation, Strengths
High temporal resolution Relatively cheap Can be used on many different samples Detects change in activity over time so can look at differences between activties Low invasiveness
Functional Brain - EEG Evaluation, Weaknesses
Signals are easily contaminated Interpretation is difficult Poor spatial resolution Cannot produce an image of the brain Takes many trials to be able to average across and filter out noise
Functional Brain - Positron Emission Tomography
Radioactive trackers (glucose) are injected
Glucose releases positrons when metabolised
Positrons collide with electrons, producing 2 photos and gamma rays which shoot out in opposite directions
Computers detect the centre of the gamma rays to identify where glucose was consumed
Higher glucose consumption indicates increased activity, if many gamma rays are released from a particular area, lots of lguocse has been consumed therefore more activity is occurring
Functional Brain - PET Evaluation, Strengths`
Produces detailed images during tasks
More sensitive than EEG
High spatial resolution due to size of glucose molecules ( 5 - 10 mm2 )
Functional Brain - PET Evaluation, Weaknesses
Invasive due to use of tracker
Low temporal resolution due to reliance on blood flow and then glucose consumption
Radiation exposure
Functional Brain - Functional Magnetic Resonance Imaging
Haemoglobin (Hb) carries oxygen, and its magnetic properties depend on oxygen saturation
MRI scans detect the blood-oxygen-level-dependent signal where differences in oxygen saturation change magnetic fields of Hb
Higher metabolism and activity would use more oxygen resulting in lower Hb oxygen levels, affecting magnetic porperties which are detected by magnets
Functional Brain - fMRI Evaluation, Strengths
Can detect activity during tasks
High spatial resolution ( 1 - 3 mm2)
Functional Brain - fMRI Evaluation, Weaknesses
Requires expert handling and interpretation
Expensive
Low temporal resolution ( 1 ms < )
May cause claustraphobia
Noisy and so may disrupt or cause brain activity
