QEEG
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QEEG transforms raw brainwave data into objective, clinically meaningful insights through a structured process of recording, cleaning, analysis and comparison.
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What is a QEEG?
A Quantitative Electroencephalogram (QEEG) is a mathematical and statistical analysis of brain electrical activity recorded through electroencephalography (EEG), usually from 19 or more channels recorded at the same time. It transforms traditional EEG signals into objective measures – such as power, coherence and frequency distribution – that can be compared against normative reference databases.
QEEG is an applied neuro- and psychophysiological assessment tool that supports diagnosis, treatment planning, monitoring and research; it is not a standalone diagnosis. Its goal is to identify and characterise patterns of brain activity and link these to a client’s symptoms. This supports neurofeedback and protocol design, other interventions and precise medication planning appropriate to the practitioner’s scope of practice, and informs referral options. QEEG is also widely applied in cognitive neuroscience.
Reasons for requesting a QEEG
These include, but are not limited to:
Informing clinical decisions
Supporting qualified healthcare practitioners – such as medical doctors, psychologists, psychiatrists, occupational therapists, functional and integrative practitioners and other allied healthcare workers – to make informed decisions about psychotherapy, medication, functional medicine, supplements, interventions, forensic investigation and more.
Guiding brain-training protocols
Guiding sensor placement and treatment protocol choices for brain-modulation techniques such as neurofeedback training, transcranial magnetic stimulation, photobiomodulation and other interventions that facilitate learning and self-regulation.
Assessing attention, mood and sleep
Evaluating attention, cognitive, mood, sleep or neurobehavioural concerns.
Identifying brainwave patterns
Identifying patterns of brainwave dysfunction that may be related to a variety of problems, such as learning and behavioural issues, emotional disorders and brain injury.
Tracking change over time
Providing pre- and post-QEEG information so professionals – and clients on a brain-regulation journey – can track changes in brainwave activity over time, and inform the choice of intervention, protocols and/or medication.
Brain injury and neurology
Assessment, rehabilitation and monitoring in traumatic brain injury (TBI), concussion and other neurological presentations.
EEG and QEEG: what they share and how they differ
Frequently asked questions relate to how EEG, QEEG and neurofeedback interact.
What they have in common
Both rest on the same physiological basis. The scalp EEG is produced by the postsynaptic membrane polarisation of pyramidal cells, and a standard EEG records electrical activity (brainwaves) representative of underlying cortical activity. Both EEG and QEEG provide valuable information about real-time brain functioning at the time of evaluation.
How they differ
Clinical EEG and QEEG share common roots in electrophysiology and instrumentation, but they have different origins, histories and priorities. In practice, EEG practitioners (neurologists and neurophysiologists) generally do not use QEEG, and may not even be aware of it; they use EEG for diagnostic purposes. QEEG, on the other hand, compares brain function from various perspectives against a normative database, and this information can be useful across various scopes of practice to inform protocols, interventions, treatment plans and/or medication.
Adapted from Q-Tips, “Table of Comparison between EEG and QEEG”.
Overlap between disciplines
EEG, QEEG and neurofeedback exist as three separate disciplines, although they overlap. Practitioners may apply each one on its own or combine two of them, while only a small number are competent in, and use, all three.
Source: Clinical EEG and Neuroscience, 2021, 52(2), 79–81. © EEG and Clinical Neuroscience Society (ECNS). Read the full article
How is a QEEG obtained?
1 EEG acquisition
Electrodes are placed on the scalp using an internationally standardised placement system (e.g. the 10–20 system), with proper impedance checks. Electrical activity is amplified and recorded under controlled conditions (e.g. eyes open/closed, resting state).
2 Data quality and artefact control
EEG data is carefully reviewed to remove artefacts (e.g. muscle activity and eye movements). Proper acquisition standards are essential for valid interpretation.
3 Epoch selection
Only artefact-free EEG segments (epochs) are selected for further analysis, although both the recorded EEG and the processed data are retained for review. Professional guidelines emphasise both visual inspection of the raw EEG and automated outputs.
4 Quantification
EEG signals are mathematically transformed (e.g. using a Fast Fourier Transform) into frequency bands: delta (about 1–3 Hz), theta (4–7 Hz), alpha (8–12 Hz), beta (13–25 Hz) and faster activity such as high beta and gamma (above 25 Hz). Exact band limits vary between databases.
5 Normative comparison
Results are compared with age-matched – and sometimes population-specific – normative databases derived from large populations. This produces statistical scores (e.g. z-scores or percentile maps on brain topographies) that show deviation from typical patterns.
6 Visualisation
Data is displayed as topographical brain maps, graphs and statistical summaries. Brain maps give a convenient schematic picture of the results of the spectral analysis. Interpretation should be done by appropriately trained professionals, as a statistical deviation does not equal a diagnosis.
7 Interpretation
QEEG findings complement clinical assessment and require expert interpretation within the full clinical picture. Over-interpretation of single metrics should be avoided.
Common QEEG metrics
Absolute power – the actual power (voltage) in the EEG and its distribution across the brain.
Relative power – the percentage of power in a band compared with the total power (e.g. relative theta as a share of delta, theta, alpha and beta combined).
Frequency ratios – slow-to-fast or fast-to-slow relationships, such as theta/beta or alpha/theta.
Z-scores – how far a value deviates from the norm, showing deficient or excessive activity at each electrode site.
Coherence and connectivity – communication and coordination between two cortical areas; too much (hyper) or too little (hypo) connectivity.
Phase relationships – the timing between two signals, reflecting the speed of information sharing between sites (increased or reduced phase lag).
Peak frequencies – the dominant frequency within a band, e.g. whether alpha is slow (closer to 8 Hz) or fast (closer to 12 Hz).
Symmetry – the left-right and front-back balance of power.
The metrics available depend on the specific database used.
Raw EEG traces are quantified and displayed as statistical brain maps.
What is a QEEG reference database?
A QEEG reference (or normative) database is a structured collection of EEG recordings from healthy individuals, organised by variables such as age, sex and recording conditions. It provides statistical benchmarks against which an individual's EEG can be compared.
Rather than interpreting EEG signals in isolation, the database allows for standardised comparisons, often expressed as z-scores that show how far a value deviates from the population mean. Comparing a person's EEG data against normative values helps identify deviations in brain function, supports a more objective assessment and guides targeted interventions such as neurofeedback.
PLEASE NOTE
A QEEG database does not diagnose conditions; it provides comparative statistical information.
BFSA policy statement on QEEG
To protect the public and maintain professional standards, BFSA has a clear policy statement:
Responsible use
BFSA supports the responsible use of QEEG in accordance with recognised professional standards and applicable guidelines, including those of relevant neurophysiology organisations.
Training and competence
QEEG acquisition and interpretation should be undertaken only by practitioners with appropriate training and competence and, where applicable, equivalent professional certification.
Standards and international guidelines
QEEG practitioners in South Africa are guided by international organisations and professional standards:
ISNR
The International Society for Neurofeedback and Research (ISNR) provides ethical principles and practice guidelines for neurofeedback and related methodologies.
ACNS
The American Clinical Neurophysiology Society (ACNS) sets out minimum technical standards for EEG acquisition.
International alignment
BFSA aligns with international standards, including the ISNR and ACNS guidelines, and with CNSSA at a national level. BFSA supports the evidence-informed, ethical and professionally regulated use of QEEG.
IQCB
The International QEEG Certification Board (IQCB) provides ethical principles and practice guidelines for QEEG, including position papers emphasising that QEEG interpretation requires appropriate training and certification by the IQCB, or supervision by qualified professionals.
Ethical and professional considerations
QEEG is a tool for assessment, not a standalone diagnostic method. Findings must be interpreted within a broader clinical or research context.
Practitioners must accurately represent their qualifications and limitations, and ethical guidelines require working within competence and scope of practice. Read our ethics documents →
Equipment and setup: a high-quality EEG amplifier, appropriate filters, sampling rate and artefact-reduction tools, with documentation of the montage, device, software and referencing method used. View equipment →
Articles and further reading are available in our Resources section.
Disclaimer: The information provided on this page is for professional and public education. Neurofeedback and QEEG should be used only by appropriately trained professionals and interpreted within the context of comprehensive clinical assessment, conventional EEG review and applicable professional standards.