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Methods Used To Study Cortical Specialisation

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There are several methods that both measure and scan the cortical functions of the brain and they both have their individual strengths and weaknesses. In a Positron Emission Tomography (PET) scan the scanner injects the patient with glucose containing radiotracers which are radioactive and emit positrons which are then picked up by the scanner. As glucose is used for energy in the body it will travel to the brain and distributes itself to the parts of the brain need it most at that time.

When it is inside the brain, the PET scanner can detect the gamma rays of radiation emitted by the radioactive glucose and produce a three-dimensional image of the brain based on the concentration of the glucose molecules inside the parts of the brain that are using it. The concentration of the glucose in the brain is influenced by the examiner by asking the patient to perform specific tasks such as making decisions, solving problems or studying memory activities.

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PET scanning is useful to psychologists as it gives information about the functioning of the brain and which areas are more active and respond in different ways depending on the tasks that are set.

This can then be linked to explain the functions occurring based on which parts of the brain are detected by the glucose to be responding. However this technique cannot be used to measure spontaneous behaviours as the scan measures only chemical concentrations in the brain and cannot measure the electrical signals that cause spontaneous behaviour. It can also be expensive due to the fact that radioactive substances are being used. There are ethical issues associated with PET scanning as injecting radioactive glucose can affect the patient’s health and could cause diseases to occur. PET scanning is used to assess the brain activity in people who have received strokes, cancer of the brain, traumas and other brain dysfunctions to see of what parts the brain are no longer functioning due to these diseases.

Another scanning technique used by psychologists is Computer-Assisted Tomography (CAT) scan. This scan consists of a machine that sends narrow x-ray beams through a patient’s head which are absorbed by parts of the brain. the absorption of the x-rays is reported back to the scanner and from the results it is able to render three-dimensional ‘slices’ of specific sections of the brain depending at which part of the brain the x-ray is fired at. This allows the examiner to see what is inside the brain without physically cutting it open. The measurements taken from the inside of the brain are then collaborated to form three-dimensional cross sections of the brain which gives the examiner a clear picture of the brain and it’s structure. CAT scanning can be used to determine areas of the brain that have suffered from swelling that may have been caused by trauma or cancer. This technique focuses on telling psychologists the structure of the brain and which parts can be seen in which places, it doesn’t measure the impulses and signals that the brain uses to function. The ethical issues raised in this technique are similar to that of PET scanning in the sense that radioactive harm can come to the patient’s body although it would not cause as much damage to the body as a PET scan. This technique is also non-invasive which means that the body is not penetrated by any needle or incision containing a substance that spreads around the body which decreases the stress to the patient.

Magnetic Resonance Imaging (MRI) scanning is carried out by firing radio waves and magnetic fields which are received by the scanner which turns the measurements into a detailed image of the brain. Hundreds of measurements are taken to produce the most precise image of the brain possible ensuring that to examiner can determine precisely what the brain contains and, if necessary, treat it. MRI scanning is used because it produces the highest level of structural detail compared to other scanning techniques. Also, using fMRI’s, psychologists can measure and study the functional detail of the brain by scanning the brain at a low resolution but at a rapid rate of every two or three seconds resulting in the ability to view the neural activity. This method is also non-invasive as there is no need to penetrate the body as the scanning takes place on the outside of the body. However it is a very expensive and time consuming method to carry out and it can cause stress to the patients because it makes a loud banging noise during its activity and this can causes distress to the patient especially in children and elderly patients. MRI scanning has been used to diagnose diseases of the brain and spinal cord which is undetectable by CAT scans, for example, sclerosis.

A Post Mortem Study is a way of studying the brain after death to attempt to explain the effects of brain anomalies and diseases such as brain tumours, strokes and trauma. It is only used on patients that are deceased if they have suffered a phenomenological affliction in their life that requires an explanation as to the cause of the disease. Psychologists are able to take a microscopic analysis of the brain tissue of an individual to study their hormones, toxins and neurotransmitters in the brain. These can then tell psychologists exactly what happened in the brain and its cause. Post mortem studies are used because it allows for the discovery of rare problems and diseases associated with certain areas of the brain. Having been discovered, these diseases can be made aware of in another patient and treatment could occur before the disease reaches being terminal. It also gives a lot of structural detail about the brain regarding the problems the patient died of, for example if a part of the brain is larger or smaller than another due to the disease.

However, the studies do not give any information about the functioning of the living brain as the brain can only be studied internally when it is deceased. It is also difficult to be sure of the cause and effect of the diseases because the process of dying could have affected the brain and therefore the disease. So psychologists may never know if the disease killed the patient or if they died from other factors. The physician Paul Broca used a post mortem study of his patient Tan to investigate why he could only say the word ‘tan’. He found that damage to Tan’s left frontal cortex resulted in his restricted speech due to contracting syphilis. Broca was able to link the deficits in speech to the damage to the brain and also concluded that language was dominant in the left hemisphere of the brain. From this we now know that the left hemisphere controls the speech centres of the brain.

Electroencephalography (EEG) is the recording of electrical activity in the brain along the scalp. It measures the level of neural activity and brain waves flowing through the brain by recording voltage fluctuations resulting from current flows within the neurons of the brain. Electrodes are placed on the head and the signals are measured over a period of 20-40 minutes. EEGs are a useful non-invasive method of viewing the brain and it does not cause any harm to the brain. Although the process is not a scan it can give psychologists information about the activity of specific areas of the brain and, unlike PET scans, can measure spontaneous behaviours as they are electrical signals rather than chemical. It is a relatively cheap and easy method to study the brain and it can easily be used to track changes over time.

However it lacks the sensitivity to track individual neurons so therefore it lacks the ability to produce a detailed scan of the signals through the brain. It also does not provide any structural detail of the brain whatsoever as the signals are interpreted as values on a computer rather than images. EEGs are used to diagnose epilepsy because the disorder displays distinct arrhythmic patterns within the neurons of the brain. It can also be useful in the study of sleep to assess brain waves during different stages of sleep by detecting changes in the level of activity flowing through the brain while a patient is sleeping. This method can also be used to determine the level of activity of the brain in someone who is believed to be brain dead by seeing whether or not there are neurons firing at all in a patient’s brain.a

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Methods Used To Study Cortical Specialisation. (2016, Jul 06). Retrieved from https://graduateway.com/methods-used-to-study-cortical-specialisation/

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