6.3.3 Ways of Studying the Brain

Ways of Studying the Brain

Brain scanning is used to study the brain, there are four brain scanning techniques
- CAT (Computerised Axial Tomography), this techniques uses an x-ray beam to produce a picture of the brain that shows the physiology of the brain, this is not a moving picture, but can show lesions on the brain
- PET (Position Emission Tomography), this technique involves injecting the patient with a radioactive glucose to produce a moving picture of the brain. The glucose goes to the seas of the brain with the most activity and so this is able to be picked up in the scan
- MRI (Magnetic Resonance Imaging), this technique records the energy produced by molecules of water once the magnetic field is reduced, it is a still picture produced
- fMRI (Functional Magnetic Resonance Imaging), this technique works in a similar way to MRI's, however, instead of measuring the energy emitted from water, it measures the energy released by haemoglobin and is a moving picture. fMRi is the brain imaging technique which the specification focuses on

fMRI works by detecting blood flow (oxygenated haemoglobin blood which reacts to the magnets) in the brain
It uses large magnets to detect oxygenised blood and show deoxygenised blood
Brain areas that are more active, need more blood flow, this is oxygenised blood
inactive or less active parts of the brain will show deoxygenated blood
Active areas can then be compared with areas that are lower in activity and can be shown on the fMRI image

Strengths of fMRI's	Limitations of fMRI's
Good spatial resolution of 1mm. Precisely identifying active brain regions and patterns of activation over time	fMRI machines are expensive and hard to build
It produces a moving picture, which allows for comparison over time	The participant/patient needs to remain very still throughout and is not allowed to move
It is a non-evasive and safe technique for patients	Due to availably and funding, the sample size if often very small

When studying the brain using EEG, electrodes are placed on the scalp and they record activity in the brain
Usually there are between 22-34 electrodes placed on the scalp but there can be any from 2-100 placed to record the brain activity
The electrodes are fitted to a cap and the cap is placed on the participant with conductive gel
The electrodes measure the activity of the cells directly below them, so the more electrodes the more detailed information and full picture of the brain it can give
The activity is displayed in brain waves, which is a series of lines showing distinct patterns
The amplitude shows the brain intensity and the frequency shows the speed of activation
Giving a picture of the brain activity underneath the electrodes

ERP uses the same apparatus and technique as EEG
They record when there is activity in reaction to a stimulus
This stimulus is presented many times
This provides data using statistical averaging
The waveform's peaks and dips show exactly when cognitive processes happen in the brain in relation to when the stimulus is presented

Strengths of EEG & ERP	Limitations of EEG & ERP
Both EEG and ERP are cheaper alternatives to studying the brain than brain imaging techniques	Both methods are only reasonably accurate, which means finer details are missed
Both methods are useful to test reliability on self reporting techniques, particularly to avoid social-desirability bias	Expertise is needed to interpret the outcome from the equipment
Both have been historically important in understanding the brain and studying it, especially related to sleep and medical diagnosis	Both EEG and ERP are not able to detect activity deep in the brain
ERP's allow researchers to isolate and study how individual cognitive process take place in the brain	Some cognitive process can not be studied using ERP as they are unable to be presented multiple times

Post mortem dissections/examinations are when a persons body, including their brain, is examined after they die
During the examination, brains are precisely cut
Researchers will examine and dissect brains of individuals who had suffered from trauma or mental illness and compare the brain with someone who had a neurotypical brain
This allows researchers to identify key function of specific parts of the brain
Broca's area was discovered by post-mortem dissection
- Broca was a neurologist
- One patient, named Louis Lebornge, who was the son of a school teacher, suffered from epilepsy throughout childhood
- Although educated and a craftsman, Lebornge eventually lost the ability to speak apart from the word tan
- He was hospitalised at the age of 30 and stayed in hospital until he died in 1861 at the age of 51
- After his death, Broca performed a post-mortem on his brain
- He found a lesion on the left temporal lobe, this was the only damage found
- As this was the only visible area of damage, Broca concluded that it was the area responsible for speech production, as Leborgne had developed a deficit in that area
- The term Broca's aphasia is used today for patients who display problems producing speech

Strengths of Post Mortem Dissection	Limitations of Post Mortem Dissection
Post Mortem dissections have been fundamental in the development of understanding brains and how they function, including understanding localisation of function	No brain activity can be measured as the research is conducted on a dead person
The individual is not alive and so cannot experience any discomfort	Brains could have been affected by the cause of death, effecting the results
	It is difficult to compare the brain after death with the functioning prior to death, any relationship found would be correlational and not causal