Ways of Studying the Brain (Scanning Techniques)

Question 1

What is fMRI?

Answer 1

Functional Magnetic Resonance Imaging.

• Indirectly measures electrical activity of neurons by recording changes in a brain blood flow while a person completes a task.
• As a particular area of the brain becomes more active, it requires more oxygen, which is supplied via the bloodstream. Blood vessels widen to provide more oxygenated blood.
• As the blood becomes deoxygenated, its magnetic properties change.
• The difference in magnetic properties is detected & converted into a computer image of the brain.
• A stable signal indicates more blood flow & therefore, high neural activity: such areas appear as bright colours on an fMRI.

Question 2

Evaluation of fMRI as a way of the studying the brain.

Answer 2

• Strength: high spatial resolution: TMT the activity of the brain whilst a person completes a task is precisely measured to an accuracy of mm. It also allows for deep area of the brain to be investigated.
• Limitation: low temporal resolution: a result of measuring neural activity indirectly in this way is around a 5sec delay b/w the neural activity & the resulting image on the computer screen.

Question 3

What is an EEG?

Answer 3

Electroencephalogram.

• Directly & continually measures general electrical activity of neurons during brain states such as sleep & arousal.
• Electrodes placed on the scalp detect small electrical changes resulting from the activity of millions of neurons.
• When electrical signals from different electrodes are recorded over a period of time, they produce an EEG graph.
• Brainwave patterns can show if the brain in a relaxed/awake state.
• An EEG can reveal abnormal neural activity, e.g. occurring during epileptic seizures.

Question 4

Evaluation of an EEG as a way of studying the brain.

Answer 4

• Strength: high temporal resolution: neural activity in the brain corresponds to an EEG graph w/ only a 1millisecond delay. Since an EEG directly measures neural activity, it can investigate brain states where the timing is important, e.g. Dement & Kleitman’s study.
• Limitation: low spatial resolution: each electrode measures general activity of many 1000s of neurons, which means the activity of specific neurons cannot be precisely localised. Furthermore, an EEG can only detect activity in the superficial, cortical layers of the brain.

Question 5

What are ERPs?

Answer 5

Event-Related Potentials.

• Very small changes in electrical activity of the brain that are elicited by specific stimuli presented to the ps (e.g. a pic).
• To establish an ERP, many EEG reading are taken whilst the same stimulus is presented & an average reading is produced.
• A consistent neural response to the stimulus will appear as a clear ERP. Any inconsistent, extraneous background activity (‘noise’) will be filtered out.

Question 6

Evaluation of using ERPs as a way of studying the brain.

Answer 6

• Strength: high temporal resolution: ERPs allow neural activity to be more precisely time-linked to the presentation of external stimuli. This can be beneficial when investigating the activity of neural areas localised for processing sensory info.
• Limitation: they only detect activity in the superficial layers of the brain: the raw data used to create an ERP readings which measure the neural activity via electrodes placed on the scalp.

Question 7

What are post-mortem examinations?

Answer 7

• Involves the analysis of a person’s brain after their death.
• If a person had a rare disorder/displayed abnormal behaviour during their lifetime, a post-mortem may establish the neurobiological cause.
• Comparisons to neural-typical brains may also be used to ascertain the extent of the differences.
• Famous examples of post-mortem examinations incl. those on Leborgne (Tan) & Henry Molaison (HM) - whose memory deficits were linked to a damaged hippocampus.

Question 8

Evaluation of post-mortems as a way of studying the brain.

Answer 8

• Strength: they facilitate investigation of deeper areas of the brain which EEGs & ERPs cannot reveal. E.g. it was only after Louis Leborgne’s death that Paul Broca was able to conduct the post-mortem examination which revealed damage to Broca’s area.
• Limitation: the post-mortem day b/w death & examination which can be up to 3 days. A related problem involves the issue of causation. Any functional deficits experiences by the person may not have bee due to the damage revealed in the post-mortem examination, but to some unrelated trauma/decay.