Advances in brain imaging technology (BIT’s) enable us to investigate the relationship between biological factors and human behaviours in greater depth. BIT’s are used to move away from more invasive techniques of studying the brain, such as liasoning – intentional scarring of the brain, and ablation – intentionally cutting out pieces of the brain. The brain imaging technologies that will be examined are electroencephalography (EEP), functional magnetic resonance imaging (fMRI), magnetic resonance imaging (MRI), and positron emission tomography (PET). These brain imaging technologies are either functional or structural. Functional BIT’s are ones that are used to identify metabolic disease and lesions on a finer scale, while structural BIT’s are ones that deal with the structural of the brain and the diagnosis of gross, intracranial disease. This essay will offer a considered and balanced review of various brain imaging technologies in the relationship between biological factors and behaviour and related studies that include a range of factors that are supported by appropriate evidence.
In the biological level of analysis, BIT’s are methods used in psychology to examine the human brain. They are useful particularly in the field of neuropsychology, as it provides an opportunity to study the brain in it’s active state. BIT’s also allow researchers to study localisation of function in a living brain as the BIT can show where specific processes take place. The BIT also allows researchers to form a correlation between human behaviour and physiological processes in the brain, however, this is not a causal relationship.
Electroencephalography (EEG) is a type of brain imaging that works through measuring electrical impulses. A large number of electrodes placed on the scalp measure the electrical activity in that area of the scalp. The resulting spikes and waves of electrical activity are recorded. The strengths of the EEG scan are numerous. It is a lot more convenient and easier to use than the other BIT’s as it is fairly tolerant to the subject moving, costs less to perform, and the EEG scanning equipment is smaller and much less bulky compared to other BIT’s. However, an EEG scan has low spatial resolution, meaning it is not easy to tell exactly what parts of the brain are active. The EEG scan also has difficulty measuring some deeper brain regions as they contribute far less to the EEG signal. Thus, EEG scans are most appropriate to use when measuring behaviour such as seizures or epilepsy. One such study is the case study of Clive Wearing. After having been struck down with amnesia, Wearing started to experience episodes of marked shaking, seizures, and repeated burping sounds. These were thought to be epileptic, and thus the EEG scan was appropriate to measure this behaviour. The results of the scan indicated increased activity in the medial temporal lobe, suggesting a relationship between the biological factor of increased activity and epileptic behaviours.
Functional magnetic resonance imaging (fMRI) is another type of brain imaging which works through detecting changes in the use of oxygen in the blood. Areas of the brain that are more active have more oxygen. Through detecting the magnetic component of blood, fMRI scans show full 3D images of brain structures. The fMRI scan has many strengths. It is very safe as no radioactive substances are used; it has high spatial resolution; and it can be used to observe the brain in it’s active state. On the other hand, a fMRI scan only can provide correlations – it cannot establish cause-effect relationships. The fMRI scan is also fairly difficult to use as it is expensive, the material is bulky, and the subject must stay perfectly still in a very small hole (also making it difficult for claustrophobics), while loud sounds are playing (diminishes the ability to use fMRI scan in studies involving auditory stimulus), and while massive magnetic fields are around them (any metal implants cannot be brought inside a fMRI scan, for example.) As a result of being a functional BIT, fMRI is appropriate for use in change in activity in the brain before and after a stimulus.
An example of this is Baumgartner et al. In Baumgartner et. Al’s study on trust, the brain imaging technology of functional magnetic resonance imaging (fMRI scan) enables us to investigate the effect that the amygdala and caudate nucleus have on trust behaviour. Due to fMRI scans being functional, the researchers could examine the change in activity in the amygdala and caudate muscles, and their subsequent role in trust. A low level of activity in the amygdala and caudate nucleus is an indication of lesser amounts of trust, as shown when activity levels decreased in the study after a breach of trust. This study shows how the functional technology of fMRI scan aided in investigating the link between the biological factor of the amygdala and caudate muscles and the behaviour of trust.
Magnetic resonance imaging (MRI) is a BIT which works quite a bit differently to fMRI, despite having similar names. MRI scanning works through by using a superconducting magnet to line up nuclei in the body. Nuclei that do not match up are detected, creating an image. MRI is safe to use as no radioactive material is used, and it can also track blood flow in the brain, which can be used to identify problems with blood circulation, such as a stroke. However, MRI, like fMRI, is difficult to use, as the subject must stay perfectly still in claustrophobic conditions in very loud sounds. It also cannot be used if the subject has metal in their body, such as an implant. This makes MRI scans most appropriate to use where extremely detailed images of the images of internal structures in the brain are required. An example of this is Maguire’s taxi driver study (2000). In Maguire et. Al’s quasi-experiment on the role of the hippocampus in spatial navigation, the brain imaging technology of magnetic resonance imaging (MRI scan) enables us to investigate the effect that the posterior and anterior hippocampus have on spatial navigation. MRI scans can give extremely detailed images of internal structures in the brain, which made MRI a suitable BIT to use in the study. The researchers could use MRI to compare the hippocampus of the taxi drivers to the hippocampus of the regular people. This study shows how MRI scans aided in investigating the link between the posterior and anterior hippocampus and spatial navigation.
Positron emission tomography (PET) scans are a BIT which utilises glucose to help generate an image of the brain. Harmless radioactive glucose is injected into the subject or consumed orally. It travels through the bloodstream to the brain where it metabolises. These radioactive particles are detected by the PET scanner which then produces a 3d image, although most researchers use a 2d slice of the image. The PET scan is non-invasive, can be used in people where MRI and fMRI cannot, can diagnose tumours in the brain, and can record ongoing activity, such as thinking. However, the glucose used in PET decays rapidly, so a PET scan cannot be used for anything other than fairly short tasks. One study that uses PET scans is
Mosconi et al in his study of Alzheimers’ disease. He conducted PET scans on Alzheimer’s patients and regular people. Alzheimer’s disease was supposed to be linked to a malfunctioning in the hippocampal area of the brain. Because an PET scan allows researchers to observe parts of the brain that respond to different functions, the PET scan is appropriate to investigate the connection between biological factors and Alzheimer’s disease. The technology is functional and the activity of the hippocampal region could be determined by the levels of radioactive glucose in the area. Low metabolic activity indicates early onset Alzheimer’s disease. This study shows how the functional technology of PET scan aided in investigating the link between biological factor of decreased hippocampal activity and the behaviour of Alzheimer’s disease.
In conclusion, all of these BIT technologies aid researchers in investigating the link between biological factors and behaviours. The studies of Clive Wearing, Baumgartner et. Al, Mosconi, demonstrate this.
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