Research Methods

Research Methods

1. EFFECTS OF BRAIN DAMAGE

   • Broca's area: inability to produce speech. e.g. "tan"
   • Wernicke's area: inability to understand language. sentences make no sense
   • Brain damage studies limitations
     • no damages the same
     • rare to have brain damage to just one area
   • AMNESIA: reterograde: can't retrieve memories before, anterograde: can't form new memories after

2. Brain stimulation

   • intense magnetic field activating neurons below
   • study behaviour with brain area active

3. STRUCTURAL BRAIN ANATOMY

   • based on gray / white matter having different properties
   • CT SCAN: die into blood, head into CT scanner, uses x-ray to create 3D image is used to detect tumours
     • POSITIVES: precise location and extent of damage, good clarity, low intrusion
     • NEGATIVES: radiation, allergic reaction, low spatial, no temporal resolution
   • MRI SCAN: uses magnetic fields and radio waves to vibrate hydrogen atoms in neurons in the brain. magnet aligns the atoms with the magnetic field
     • radio frequency knocks the protons which produces changes which are measured
     • POSITIVES: determines damage and abnormalities, low intrusiveness,, high spatial resolution (1-2mm)
     • NEGATIVES: cant be used with metallic devices, no temporal resolution, claustrophobia
   • correlates brain activity with behaviour

4. EXPLAINING METHODS

   • Phrenology: Joseph Gall, different regions perform different functions.
   • Pathology: studying the brain after death, but problems with sample and can't establish cognitions
   • Jerison: more brain mass, more complex behaviours
   • Spatial resolution: how much detail about the brain (WHERE)
   • Temporal resolution: how much detail the method provides (TIMING) (WHEN)
   • ablation: removal of brain area. lesion: damage
   • neither total brain mass or brain to body ratio shows humans as most intelligent

5. FUNCTIONAL BRAIN ANATOMY

   • moment-by-moment maps of activity created
     • neural activity produces changes in the brain
   • EEG: electroencephalogram
     • continuous recording of electrical activity, records groups of neurons firing at once. measures differences between electrodes on the scalp.
     • raw EEG not sensitive enough, uses ERP where signals are averaged
     • POSITIVES: cheap, non invasive, used for long periods of time,can be used on a range of subjects, used during tasks, high temporal resolution (1 msec)
     • NEGATIVES: signal can be contaminated by blinks, cant determine areas to functions, ERP uses a large number of trials to average. low spatial res
     • evoked potentials similar to eeg but in response to stimuli
   • PET: positron emission tomography
     • injected with radioactive tracer, tracer releases a positron which collides with electron and produces photons. active brain regions emit most photons
     • POSITIVES: detailed images during task, colour images, moderate spatial resolution (5-10 mm3)
     • NEGATIVES: invasive, radioactive, limited to 3 scans a year, low temporal resolution
   • fMRI: functional magnetic resonance imaging
     • fMRI based on level of metabolism in the brain. hemoglobin. detects changes in blood oxygen, increased activity = increased oxygen
     • fMRI measures differences between experimental and comparison task and compares
     • POSITIVES: images during a task. more sensitive than CT or MRI (structural), colour, low invasivness, high spatial resolution
     • NEGATIVES: technical expertise needed, expensive, interpreting is hard, low temporal resolution
   • MEG: magnetoencephalogram, measures magnetic fields. closely related to EEG. magnetic field passes through brain and then neural currents measured.
     • POSITIVES: non-invasive, can test on children, repeat testing, good spatial resolution, good temporal resolution
     • NEGATIVES: expensive, MEG needs to be done in specially constructed rooms, MEG doesnt provide structural info. risk of helium shortage
   • records brain activity during behaviour

6. TMS: intense magnetic field to portion of the scalp which activates neurons below

7. Gilmore et al. 2007, men and women have different brain sizes but equal IQs

8. differences in ability not found to be due to brains size or ability but due to differences in socialisation