studying the brain

What are the 4 kinds of techniques to study the brain?

• Functional magnetic resonance imaging (fMRI)

• Electroencephalogram (EEG)

• Event-related potentials (ERPs)

• Post-mortem examinations

How does fMRI work?

• The brightness of the image sows neural activity - brighter = more activity

• Sends a magnetic pulse

• Measures blood flow in the brain

• Neural activity requires energy - oxygen: haemoglobin becomes deoxygenated, the different magnetic quality detected

• Shows activity about 1-4 seconds after it occurs - accurate within 1-2 mm

• Increase in blood flow due to need of more oxygen in the brain

What is an example of MRI being used?

Maguire’s taxi driver - whether structural changes could be detected in the brain of people with extensive experience of spatial navigation

• Structural MRI scans

• 16 right handed taxi driver (>1.5 years experience) compared with 50 healthy men who didn’t drive taxis

• Age didn’t differ between the groups

= Increased grey matter was found in the brains of taxi drivers compared with controls in 2 brain regions, the right and left hippocampi

= Correlation found between the amount of time spent as a taxi driver and volume in the right posterior hippocampus

Suggesting that extensive practice with spatial navigation affects the hippocampus

What are the strengths of fMRI? (AO3)

• Good spatial resolution - allows discrimination between brain regions

• Partial application - research, diagnosis

• Very safe - decades of use, no evidence of human harm, animals raising offsprings in fMRIs - non invasive

What are the limitations of fMRI? (AO3)

• Lacks temporal resolution

• Expensive - equipment, specialists…

• Don’t provide a direct measure of neural activity - simply measures blood flow, cannot conclude whether this brain region is associated with a particular function, research found that the right hemisphere is active before the left = unconscious control our thoughts, but fMRI makes conscious decisions

How does EEG work?

• Continuous recording of electrical brain activity

• Reading the post-synaptic electrical neuron

• Measured in microvolts

• 4 types of wavelength: Gamma, Beta, Alpha, Theta

• Equipment: EEG cap, EEG amplifier, data acquisition computer

Step by step process of EEG

1. Pour 1L of distilled water into bucket

2. Mix in potassium chloride

3. Mix in shampoo - improve electrical reading

4. Measure the participant’s head - diameter

5. Select the right cap + soak it in solution for 10 mins

6. Measure from jaw bone to jaw bone

7. Measure from nails on to inion

8. Start the software

9. Place EEG cap on participant’s head

10. Wiggle the electrode - lower impedance (electrodes are laid out in a universally approved way) + add more solution

What is am example of EEG being used?

Dement and Kleitman - stages of sleep

• Used EEGs to measure activity in different stages of sleep

• Lab experiment - no caffeine or alcohol

• Volunteer sampling

• 7 males, 2 females - 9 participants - small sample

• EEG patterns as active in dreams and awake

How does ERPs work?

• Same as EEG

• But it has a stimulus and controlled point

• Baseline - time period before stimulus

What are the strength of EEG and ERPs? (AO3)

• Practical application - used in research and diagnosis

• Fast, high temporal resolution - can record in milliseconds

• Safe - doesn’t affect the brain

• Cheaper than an fMRI scan

What are the limitations of EEG and ERPs? (AO3)

• Cultural bias - developed based on eastern hairs - ineffective on some hair types, but has been addressed

• Poor spatial resolution - don’t know where in the brain the activity is

How does post-mortem examinations work?

• Standard procedure

• Samples may be taken from specific areas or structure

• Some samples may be taken for microscopic inspection

• Comparisons are made with healthy brains - checking the eternal parts: membranes and blood vessels, then cut through mammillary body, half-cm slices

What is an example of post-mortem examinations being used?

• Broca - examined the brain of a man who only repeated ‘tan’ - discovered that he had a lesion in the area of the brain important for speech production - Broca’s area

• Wernicke - discovered a region in the left temporal lobe, which is important for language comprehension

• HM

• Iverson found a higher concentration of dopamine in the limbic system of patients with schizophrenia which has prompted a whole area of research looking into the neural correlates of this disorder

What are the strengths of post-mortem examinations? (AO3)

• Highly standardised, replicable

• Has given insight (e.g. Broca)

What are the limitations of post-mortem examinations? (AO3)

• Socially and ethical concerns - consent (e.g. HM)

• Can only establish a correlation - can’t establish cause and effect

• Patients must be deceased