Biopsychology: Studying the Brain - Evaluation of EEG & ERP

Here are some key evaluation points relating to Electroencephalogram (EEG) & Event-Related Potentials (ERP).

Invasive or Non-Invasive

An advantage of EEG and ERP is that both techniques are non-invasive. Unlike other scanning techniques, such as Positron Emission Tomography (PET), EEG and ERP do not use radiation or involve inserting instruments directly into the brain and are therefore virtually risk-free. Furthermore, EEG and ERP are much cheaper techniques in comparison with fMRI scanning and are therefore more readily available. Consequently, this should allow more patients/participants to undertake EEG/ERPs, which could help psychologists to gather further data on the functioning human brain and therefore develop our understanding of different psychological phenomena, such as sleeping, and different disorders like Alzheimer's.

Spatial Resolution

However, one disadvantage of EEG/ERP is that these techniques have poor 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. EEGs/ERPs only detect the activity in superficial regions of the brain. Consequently, EEGs and ERPs are unable to provide information on what is happening in the deeper regions of the brain (such as the hypothalamus), making this technique limited in comparison to the fMRI, which has a spatial resolution of 1-2mm.

Temporal Resolution: An advantage of the EEG/ERP technique is that it has good temporal resolution: it takes readings every millisecond, meaning it can record the brain’s activity in real time as opposed to looking at a passive brain. This leads to an accurate measurement of electrical activity when undertaking a specific task.

However, it could be argued that EEG/ERP is uncomfortable for the participant, as electrodes are attached to the scalp. This could result in unrepresentative readings as the patient’s discomfort may be affecting cognitive responses to situations. fMRI scans, on the other hand, are less invasive and would not cause the participants any discomfort, leading to potentially more accurate recordings.

EEG: Another issue with EEG is that electrical activity is often detected in several regions of the brain simultaneously. Consequently, it can be difficult pinpoint the exact area/region of activity, making it difficult for researchers to draw accurate conclusions.

ERP: However, ERPs enable the determination of how processing is affected by a specific experimental manipulation. This makes ERP use a more experimentally robust method as it can eliminate extraneous neutral activity, something that other scanning techniques (and EEG) may struggle to do.