Section B – Biopsychology: Q9 [8 Marks]
Functional magnetic resonance imaging (fMRI) is a brain-scanning technique that measures blood flow in the brain when a person performs a task. fMRI works on the idea that the neurons in the brain which are the most active, use the most energy (in the form of oxygen and glucose). Deoxygenated and oxygenated haemoglobin have different magnetic qualities. An fMRI scanner can detect these different magnetic qualities and can be used to create a moving 3D map of the brain.
An electroencephalogram (EEG) measures electrical activity through electrodes attached to the scalp. EEG scanners work on the idea that information is processed in the brain as electrical activity in the form of action potentials or nerve impulses. Small electrical charges are detected by the electrodes that are graphed over a period of time, indicating the level of activity in the brain. EEG can be used to detect illnesses like epilepsy and to diagnose other disorders that affect brain activity, like Alzheimer’s disease.
An advantage of the EEG, in comparison to fMRI, is that it has good temporal resolution. Temporal resolution refers to the accuracy of the scanner in relation to time: or how quickly the scanner can detect changes in brain activity. EEG scanners take readings every millisecond, meaning it can record the brain’s activity in real time as opposed to looking at a passive brain. However, fMRI scans have a temporal resolution of 1-4 seconds which is worse than other techniques (e.g. EEG). This suggests that EEG can provide a high degree of accuracy when examining the onset of brain activity, allowing psychologist to make accurate conclusions in relation to the timing of neural activity, in comparison to fMRI.
However, one strength of fMRI, in comparison to EEG, is that it has good spatial resolution. Spatial resolution refers to the smallest feature (or measurement) that a scanner can detect, and is an important feature of brain scanning techniques. Greater spatial resolution allows psychologists to discriminate between different brain regions with greater accuracy. fMRI scans have a spatial resolution of approximately 1-2 mm which is significantly greater than the other techniques. EEG, on the other hand, can only detect the activity in superficial regions of the brain. Therefore, psychologists can determine the activity of different brain regions with greater accuracy when using fMRI, in comparison to when using EEG, which makes fMRI an ideal choice when trying to pinpoint specific brain regions.
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