Lesson 10 - Ways of studying the brain

Question 1

fMRI

Answer 1

• Developed from the MRI
• Based on the principle that neurons that are most active will require more energy. This is in the form of glucose and oxygen in the bloodstream
• Therefore, the more active an area of the brain is, the more blood will flow to that part
• fMRI scans measure blood flow by detecting the concentration of oxygen using the BOLD contrast (‘Blood Oxygen Level Dependent’ imaging)
• Has been applied to lie detection over the conventional test

Question 2

Strengths of fMRIs

Answer 2

• fMRIs are not invasive and do not rely on radiation like PETs. It is virtually risk free. As a result of this simple and risk free procedure, more people should be able to have fMRIs which can develop our understanding of localisation of function
• They have good spatial resolution. This means that we can detect activity in very small areas of the brain and we can discriminate between regions with greater accuracy. The spatial resolution is around 1-2mm. This is much greater than EEG and ERPs.

Question 3

Weaknesses of fMRIs

Answer 3

• We are only indirectly measuring neuronal activity through oxygen, and we cannot fully deduce function from this. It also fails to show any type of communication between areas of the brain.
• They have a poor temporal resolution, meaning there is a latency of around 1-4 seconds, so it is difficult to accurately detect the onset of brain activity.

Question 4

Electroencephalogram

Answer 4

• The EEG was developed in 1929 by Hans Berger
• 16-25 small electrodes are placed over the skull and they pick up the electrical activity of millions of neurons
• It detects the amplitude of the electrical activity and the frequency (speed/rapidity) of the activity
• The EEG has two distinguishable states:

Synchronised pattern - there is a recognisable waveform that can be seen in the EEG recording

Desynchronised pattern - there is no recognisable pattern

• The EEG can be used to detect various types of brain disorder like epilepsy

Different kinds of waves can be found in EEGs like beta, alpha, theta and delta waves.

Very useful in studying sleep patterns, stages of sleep and general state of the brain

Question 5

Strengths of the EEG

Answer 5

• Provides a recording of the brain in real time instead of producing a still image, and this is useful when looking at the brains activity during a particular activity, like a cognitive task. They also have a good temporal resolution unlike an fMRI
• It has also provided very significant diagnoses of neurological conditions like epilepsy.
• It has contributed to our understanding of the sleep cycle

Question 6

Weaknesses of EEG

Answer 6

• It can only detect activity close to the surface of the brain, so it cannot reveal information about deeper areas such as the hypothalamus and hippocampus. As the hippocampus is significant in the long term memory, it is difficult to attain an understanding of this through the EEG.
• They have a poor spatial resolution, so it is difficult to distinguish between different areas

Question 7

Event-related potentials

Answer 7

• ERP’s are very small changes in voltage triggered by specific events or stimuli. An example could be the cognitive processing of an image
• Like an EEG, there are a series of electrodes that are placed over the skull.
• However, instead of reading waves like an EEG, the psychologist looks for a specific electrical response in the brain.
• An issue that can arise is how do you differentiate between the general electrical noise of the brain and specific stimuli-related responses?
• To counter this, the stimuli (image, sound) is presented several times, and this is layered on top of each other so the stimuli-related responses add up, while the background noise cancels out. An ERP image emerges

Question 8

Strengths of ERPs

Answer 8

There is a very short latency period between the presentation of stimuli and the ERP. It can reflect the early stages of cognitive processing, like working memory and facial processing

Question 9

Weaknesses of ERP’s

Answer 9

• Like EEGs, they have poor spatial resolution, so we cannot achieve a deeper understanding about localisation of function from ERPs
• There is a lack of standardised method to ERP procedures, so it is questionable whether we can generalise ERP results.
• Extraneous variables like background electrical noise cannot always be minimised

Question 10

Post-mortem examinations

Answer 10

• A typical use for post-mortems includes studying a person’s behaviour while they are alive, under the assumption of underlying brain damage. When they are dead, you can study their physical brain for any abnormalities that explain these behaviours. Broca and Wernicke both used this to greaten understanding of the language centre

Question 11

Weaknesses of post mortems

Answer 11

• There are several confounding variables in post mortem examinations: drug treatments, the age of death, length of time between death and examination etc. Therefore we cannot make generalisations about brain functioning due to individual differences
• There is an issue with consent and whether or not this was given prior to death. In the case of HM for example who had a post mortem conducted after death, in his state of severe amnesia, they would not have been able to give fully informed consent

Question 12

Strengths of post mortems

Answer 12

• They provide a more detailed and deeper analysis of the anatomy of the brain
• It has very practical implications: Iverson was able to find a higher concentration of dopamine in the limbic system of schizophrenic patients. This started an area of research into neural correlates of schizophrenia