For this reason, an EEG test should not be used to diagnose and is used alongside other clinical tests and inquiries. However, abnormal EEG results do not always prove that the person has a brain disorder, nor does a normal EEG guarantee the absence of brain pathology. They are often characterized by focal or generalized sequences of sharps and spikes components (Emmady and Anilkumar, 2020 Medithe and Nelakuditi, 2016). Epileptic seizures are unusual EEG patterns caused by severely disturbed changes in brain activity. Another typical example of abnormal waveform patterns linked to a neurological disorder is seizures. S ome signs of abnormal EEG include inappropriate scalp location of frequencies or irregularities in brain wave amplitudes.įor example, a persistent “slowing” activity in the EEG background of an awake adult person is not normal (Sazgar and Young, 2019). Normal EEG data shows regular and symmetrical brain wave traces, often characterized by a dominant frequency in a specific scalp location. For instance, in a normal awake person, the Alpha rhythm is detected in posterior head regions while Beta rhythm is typically localized in frontal areas. Normally, this observed EEG pattern varies according to the level of alertness, fatigue or cognitive engagement (Sazgar and Young, 2019).Īn EEG test is considered to be abnormal when the pattern of brain activity shows unusual features which do not match the person's level of alertness, neurodevelopment stage, and other neurobiological factors. Usually, typical brain waves observed in an EEG register are categorized as Alpha (8-15 Hz), Beta (16-30 Hz), Theta (4-7 Hz), Delta (1-3 Hz), and Gamma (>30Hz). These signals are recognized by their morphology and frequency. The electroencephalography is characterized by typical neural rhythms oscillating at specific frequencies known as brain waves (Kumar and Bhuvaneswari, 2012). However, to perform an accurate analysis, it is important to have a basic understanding of what normal/abnormal activity means in EEG (Medithe and Nelakuditi, 2016). The EEG test is the procedure of recording and monitoring brain activity with an electroencephalogram, following specific steps to gather meaningful data for the specific purpose of its application.ĮEG test results can shed light on possible abnormalities in the brain electrical activity. Today´s EEG systems are portable, allowing for more ecological data collection in real-world environments (e.g., at a participant’s home).
Excellent time resolution, allowing non-invasive access to brain activity within tens of milliseconds.These sensors are capable of accurately picking up the activity of neurons in different parts of the brain in the time frame in which brain processes occur (e.g., 80-400ms).ĮEG devices have two clear advantages (Cohen, 2011):
An EEG is an electrophysiological recording device that measures, in real-time, the electrical field that results from neural activity (microvolt signal).Ī typical EEG system uses one or multiple sensors (electrodes usually in the shape of small metal discs) placed in different sites on the head, usually according to the 10/20 system landmarks (Jasper, 1958). When thousands of these brain cells fire at the same time, they generate small currents that can be detected on the head surface with a right device (Jung & Berger, 1979). Our brains contain neurons that are deeply interconnected through synaptic mechanisms.
To better understand what an EEG test is, first we must understand what an EEG is.
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