This cap contains between 16 and 25 flat metal discs called electrodes, which measure the electrical activity of the brain. ERPs that occur after 100 milliseconds are referred to as cognitive ERPs, as they demonstrate some information processing.During an EEG test, a skilled EEG technician will place an electrode cap on the person’s head. Waves (responses) that occur within 100 milliseconds following the presentation of a stimulus are referred to as sensory ERPs, as they reflect a sensory response to the stimulus. ERPs have a very short latency and can be divided into two broad categories. The time or interval between the presentation of the stimulus and the response is referred to as latency. This procedure, which is called ‘averaging’, reduces any extraneous neural activity which makes the specific response to the stimulus stand out. However, as ERPs are difficult to separate from all of the background EEG data, the stimulus is present many times (usually hundreds), and an average response is graphed. However, the key difference is that a stimulus is presented to a participant (for example a picture/sound) and the researcher looks for activity related to that stimulus.
Furthermore, EEG scanning was responsible for developing our understanding of REM (dream) sleep, which is associated with a fast, desynchronized activity, indicative of dreaming.ĮEG can also be used to detect illnesses like epilepsy and sleep disorders, and to diagnose other disorders that affect brain activity, like Alzheimer’s disease.Įvent-Related Potentials (ERP) use similar equipment to EEG, electrodes attached to the scalp. A synchronised pattern is where a recognised waveform (alpha, beta, delta and theta) can be detected, whereas a desynchronized is where no pattern can be detected.įast desynchronized patterns are usually found when awake and synchronised patterns are typically found during sleep (alpha waves are associated with light sleep, and theta/delta waves are associated with deep sleep). Frequency: the speed or quantity of activityĪlso, EEG patterns produce two distinctive states: synchronised and desynchronized patterns.Amplitude: the intensity or size of the activity.Each of these patterns has two basic properties that psychologists can examine: There are four types of EEG patterns including alpha waves, beta waves, theta waves and delta waves.
Small electrical charges detected by the electrodes are graphed over a period of time, indicating the level of activity in the brain. EEG scanners measure this electrical activity through electrodes attached to the scalp. An electroencephalogram (EEG) works on the premise that information is processed in the brain as electrical activity in the form of action potentials or nerve impulses, transmitted along neurons.
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