EEG test: Uses, Procedures and Risks

EEG test: Uses, Procedures and Risks

10 Min.
By Cristina Gil-López and Javier Mínguez
March 26, 2024

The Electroencephalogram (EEG) is a cost-effective, scientifically-proven method to examine brain activity linked to multiple neurocognitive processes that underlie human behavior. The non-invasive nature of EEG makes it an optimal assessment tool to detect abnormal brain activity in different types of patients. The results of the EEG test provide accurate knowledge of the human brain while gaining deeper insights into underlying neural mechanisms of cognition. In this post, we highlight some of these applications, procedures, and advantages of using EEG recordings in research and medical settings.

What is an EEG test?

We must understand what an EEG is to better understand what is an EEG test. 

Neurons in our brains are deeply connected through synaptic mechanisms. When many brain cells in the cerebral cortex fire together, they generate small currents and electrical impulses that a device can measure on the surface of the head. An EEG is a device that records the electrical signals from brain activity in real-time (Jung & Berger, 1979). It measures microvolt signals. 

An EEG system uses sensors, like small metal discs, on the head. These EEG electrodes are placed based on the 10/20 system landmarks (Jasper, 1958). These sensors can accurately detect neuron activity in different areas of the brain. They can do this within the time frame of brain processes, which is typically between 80 and 400 milliseconds.

Although the routine EEG is typically conducted in a stationary setting, ambulatory EEG allows the patient to wear the device during their daily activities or perform an EEG test at home.

EEG systems have two clear advantages (Cohen, 2011): 

  1.  Great time accuracy, can quickly detect changes in brain activity in milliseconds without invasive methods. These changes happen faster than blinking.
  2. Relatively inexpensive and adaptable to different contexts compared with other brain assessment devices such as magnetic resonance imaging. Modern EEG systems are portable and can be easily taken to different locations. This allows for data collection in real-life settings such as a person's home.

The EEG test or electroencephalogram is the procedure of recording electrical activity of the brain with sensors over the scalp.

EEG tests can show if there are abnormalities with the brain's electrical activity. It is important to know what normal and abnormal activity looks like in EEG to analyze the results accurately (Medithe and Nelakuditi, 2016). 

In the next Figure we display different type of EEG system ranging from research to applications:

Versatile EEG, Diadem EEG and Neuroheadband EEG

Normal EEG brain activity

The electroencephalogram (EEG) is characterized by neural rhythms oscillating at specific frequencies, commonly referred to as brain waves (Kumar and Bhuvaneswari, 2012). These signals are identified based on their morphology and frequency. Typically, the EEG registers several types of brain waves, including Alpha (8-15 Hz), Beta (16-30 Hz), Theta (4-7 Hz), Delta (1-3 Hz), and Gamma (>30 Hz).

Brain Waves Bitbrain

In normal EEG data, brain wave patterns and traces exhibit regularity and symmetry, often featuring a dominant frequency at specific scalp locations. For example, in a wakeful individual, the Alpha rhythm is commonly observed in posterior head regions, while the Beta rhythm tends to localize in frontal areas. This pattern typically fluctuates according to the individual's level of alertness, fatigue, or cognitive engagement (Sazgar and Young, 2019).

Abnormal EEG brain activity

An EEG test is considered abnormal when the pattern of brain activity shows unusual features that don't align with the individual's level of alertness, neurodevelopmental stage, or other neurobiological factors. Signs of an abnormal brain activity may include brain activity appearing in inappropriate scalp locations, or irregularities in wave frequencies or amplitudes.

For instance, persistent "slowing" activity in the EEG background of an awake adult is considered abnormal (Sazgar and Young, 2019). Another typical example of abnormal waveform patterns associated with neurological disorders is seizures. Epileptic seizures manifest as unusual EEG patterns resulting from severely disturbed changes in brain activity. They are often characterized by focal or generalized sequences of sharp and spike components (Emmady and Anilkumar, 2020; Medithe and Nelakuditi, 2016).

Seizures Classification Table

It is important to note that abnormal EEG results do not always confirm the presence of a brain disorder, just as a normal EEG does not guarantee the absence of brain pathology. Therefore, an EEG test should not be solely relied upon for diagnosis, but rather used in conjunction with other clinical tests and assessments.

What is an EEG test used for?

The information obtained from EEG tests is highly valuable and has many potential applications.

In medical applications, doctors use EEG recordings to detect patterns of electrical activity associated with various brain conditions or neurological disorders. Achieving accurate the results interpretation and effective patient management requires a comprehensive understanding of brainwaves and a minimal level of technical qualification.

EEG tests are important in research, especially for studying how the brain works during different experiments to understand human thinking. Neuroscientific theories explain how EEG signals are connected to cognition and emotions. (Cohen, 2011; Dvorak et al., 2018).

EEG is a favored method for examining subtle brain activities that are not directly affected by overt behavior, like inhibitory reactions that are automatically initiated during activities like driving a car. (De Sanctis et al., 2012; Zander et al., 2017).

1. The EEG test as a neurological assessment method 

The primary goal of utilizing EEG in healthcare environments is to assist physicians in determining an accurate diagnosis and formulating an appropriate treatment strategy for a possible medical condition. By expertly interpreting EEG data and combining it with a clinical assessment, an EEG test can aid in the detection of various neurological disorders, such as:

  • Seizure/Epilepsy: through the analysis of epileptiform patterns shown by the EEG traces such as 3-Hz spike-and-wave (Westmoreland, 1996), doctors can identify the seizure activity locus and, in some cases, the type of epilepsy.
  • ADHD: Neural markers associated with signs of inattention can be detected using EEG tests. Abnormal EEG patterns linked to this attention deficit include an increase in the Theta/Beta Ratio over frontal and central brain areas (Barry et al., 2003; Lenartowicz & Loo, 2014).
  • Sleep disorders: EEG testing is commonly used to evaluate sleep quality and diagnose related disorders. For example, it is recommended for patients suspected of sleep anomalies such as sleep deprivation, insomnia, and hypersomnia, among others (Verma et al., 2016; Zhu, Li & Wen, 2014).
  • Other uses in health care include detection of neurological impairments such as head injuries, strokes, tumors and dementia. Also used to monitor neural activity during brain surgery, coma states, or to confirm brain death (Teplan, 2002). 

Bitbrain Neuroheadband EEG

2. The EEG test as a brain research method

EEG is an excellent research tool in the study of neural correlates and mechanisms of cognitive functions. The insights provided contribute significantly to our understanding of the human brain, with findings having valuable applications in clinical, epidemiological, and healthcare settings.

Often, researchers use EEG to study the following two aspects: 

  • Spontaneous EEG: the investigation of brain changes associated with certain mental states such as cognitive workload or fatigue (Charbonnier et al., 2016). 
  • Task-related EEG activity: it involves the examination of evoked or event-related potentials triggered by the presentation of visual or auditory stimuli, or in conjunction with the performance of specific cognitive tasks (Luck, 2014). Examples of stimuli used to study evoked responses include the presentation of words, images, and sounds in various task contexts.

By focusing on contributions to cognition and brain health domains, EEG is particularly enlightening to address the following areas of research:

Rehabilitation brain-computer interface

  • Cognitive Sciences: they encompass the study of underlying brain correlates associated with cognitive domains such as perception, attention, memory, learning, and emotion. EEG research in this field focuses on identifying key features such as the time course, event related potentials ERP waveforms, and dominant brain frequencies that characterize cognitive performance and skills (Pietto et al., 2018; Woodman, 2010).

Bitbrain Versatile EEG

  • Clinical Psychology and Neuropsychology: EEG monitoring offer insights into specific neural markers associated with affective, neurological, and neurodevelopmental disorders. Empirical EEG results play a crucial role in guiding clinicians and therapists in the development of effective interventions (e.g., Lau-Zhu et al., 2019).

Eeg Test Neuropsychology

  • Social Psychology and Educational Sciences: Understanding the underlying brain mechanisms associated with social interaction and teaching-learning processes enables researchers to delve into various aspects of human behavior, such as attitudes, communication, social bias, motivation, and individual differences. This expanded scope of research facilitates exploration in more naturalistic environments, such as studying social interaction in virtual reality settings; Parsons, Gaggioli & Riva, 2017).

Eeg Test Education

Neuromarketing EEG Bitbrain

Procedures, Risks and Side Effects of the EEG test

The EEG process is generally safe and entails minimal risks or side effects, with little discomfort for participants. However, EEG procedures may vary depending on the context like in routine EEG test, ambulatory EEG test or EEG sleep deprived test among others.

In typical health care settings, EEG procedures prioritize patient comfort. While the preparation is painless, it may take at least 20 minutes for experienced EEG technicians to complete.

Patients scheduled for an EEG test should always adhere to specific medical advice provided beforehand, as individual health information may differ. This advice applies equally to participants undergoing EEG tests for research purposes.

Upon arrival at the research lab, clinic unit, or doctor's office, EEG test preparation typically includes:

  1. Set up: EEG preparation, electrode placement attached to the scalp and impedance lowering.
  2. Signal Quality Check: Signal quality testing and calibration.
  3. Instructions to the patient may include lying still and relax, open and/or close your eyes, deep breathing, stimuli attention, etc. Other typical activation procedures include fast eyes opening and closing for several times, photic stimulation (e.g. staring at flashing lights), breathing deeply or rapidly (hyperventilation), and sleep deprivation (staying up the entire night before the test).
  4. Recording interval during which EEG brain data is collected. Sometimes EEG video recording is also carried out.
  5. Disassembling: Remove the electrodes from the patient's scalp after the test is completed. If electrolytic substances were used, you may be asked to wash your hair.

Blog  Collage Egg Test

In the context of research, the procedures are similar, but EEG devices often involve a larger number of electrodes attached to the participant's scalp. This can significantly increase both the preparation time and the total duration of the session.

Additionally, instructions given to volunteers may vary based on the requirements of the experimenter. For example, participants may be asked to engage in mentally stimulating activities such as reading sentences, viewing images, answering questions, or listening to sounds/music, among other tasks (Pivik et al, 1993). 

Recent technological developments have significantly streamlined EEG testing. Many modern EEG devices eliminate the need for electrolytic gel, and thus the requirement to wash the head after the session. Examples are the Bitbrain Versatile EEG (use of tap water), Minimal EEG (dry metal sensors) or Textile EEG (dry textiles sensors). Additionally, adaptations have been made to conduct EEG tests for kids, such as the Bitbrain Versatile EEG. These advancements have not only improved the time and complexity of EEG setup but also made it easier for technicians without extensive prior EEG experience to collect high-quality brain data effortlessly.

What is an EEG technician?

An EEG technician, also referred to as an electroencephalography specialist or EEG professional, is a healthcare expert skilled in conducting EEG examinations and aiding in the assessment of brain function.

Eeg Activity Bitbrain

Their usual duties encompass:

  1. Preparing patients/participants for EEG examination: This includes briefing patients/participants about the process, ensuring they are comfortable throughout the test, and positioning them appropriately for electrode attachment.
  2. Electrode placement: EEG technicians affix small electrodes at specific points on the scalp using a conductive gel or paste. These electrodes capture the electrical signals produced by the brain.
  3. Operating EEG equipment: EEG tech are skilled in operating EEG machines and software to track and record brain activity during the examination.
  4. Monitoring patients/participants during the test: EEG technicians monitor patients for any signs of discomfort or unease during the test and make necessary adjustments.
  5. Troubleshooting technical issues: In case of any technical issues with the EEG equipment or recordings, EEG technicians are tasked with troubleshooting and fixing them.
  6. Record keeping: EEG tech keep precise records of EEG tests, including patients/participants details, test outcomes, and any pertinent medical history.
    In essence, EEG technicians are vital in performing EEG tests, guaranteeing precise recordings, and aiding healthcare professionals in diagnosing and managing neurological disorders.


An EEG test is a brain assessment method in which it is recorded brain activity with an EEG device, allowing high time accuracy in a relatively non-invasive and inexpensive way. The EEG procedure is easy and entails no particular risk for most patients and participants. 

There are many practical applications of this test that include clinical and research contexts. In medical settings, it is mostly used to help diagnose neurological conditions such as seizure disorders. EEG provides a worthwhile, efficient, and safe tool to assess many types of patients.

In research settings, EEG is an efficient method to study brain-behavior relationships linked to many cognitive processes. When combined with other biometric techniques, EEG test results are highly insightful in understanding human cognition and emotion in a more comprehensive way.

About the authors

Cristina Gil-López, Ph.D. (LinkedIn, Scholar, homepage) - Researcher at the Psychology and Neurocognition institute (LPNC), University of Grenoble (France) / Associated Research Scientist at Polytechnic University of Valencia (Spain)

Javier Mínguez (LinkedIn, ScholarTwitter) Associate professor of the University of Zaragoza and co-founder of Bitbrain. 

About Bitbrain solutions

Bitbrain specializes in developing innovative devices with excellent usability for multimodal monitoring, encompassing semi-dry EEG, dry-EEG, and textile-EEG systems, as well as biosignals (ExG, GSR, RESP, TEMP, IMUs, etc.), and eye-tracking solutions (screen-based and mobile platforms).

The software tools facilitate the design of experiments, effortless data gathering with over 35 synchronized sensor types, and extensive data analysis covering a broad spectrum of emotional and cognitive biometrics.

Bitbrain's platforms offer interconnectivity with other systems through LSL, ePrime, Matlab, or Python, providing flexibility and compatibility for diverse research and application needs.

Our systems are used by scientists in high-impact and peer-reviewed publications in a wide range of research applications, including neuroscience, psychology, education, human factors, market research and neuromarketing, and brain-computer interfacing

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