Measure
EEG · QEEG · ERP
- Person
- Sensors
- Recorded data
A measurement describes a recording. It does not by itself train a skill, diagnose a condition, or deliver stimulation.
THE LEARNING CENTERKnowledge that connects
Knowledge that connects
science to practice.
Explore technologies, examine primary sources, and build a more informed clinical conversation.
THE FEEDBACK LOOP
How EEG neurofeedback turns a signal into practice.
The screen is the visible part. Behind it, the provider is selecting a signal feature, checking its quality, and connecting the training to a meaningful goal.
- 01
Record
Scalp sensors read the selected EEG signal.
- 02
Translate
Software turns a chosen signal feature into a training rule.
- 03
Respond
A sound, image, or activity changes when the rule is met.
- 04
Practice and review
You practice while the provider watches signal quality and your response.
Important distinction: In conventional EEG neurofeedback, the scalp sensors record activity. They do not send electricity into the brain. Stimulation methods work differently.
UNDERSTAND THE APPROACH
What is it, and how does it work?
A practical foundation for patients and clinicians beginning to explore these approaches.
THREE DIFFERENT ROLES
Is the technology measuring, training, or stimulating?
Start with what crosses the boundary between the person and the technology. The categories can be combined in research, but they answer different questions.
Train
Neurofeedback · HRV biofeedback
- Signal
- Feedback rule
- Practice
A measured signal changes sound, images, or another cue during practice. Meaningful outcomes still need to be tracked beyond the screen.
Stimulate
PBM · TMS · PEMF
- Device
- Delivered energy
- Target
Light or magnetic energy is applied using a defined protocol. Device, dose, target, screening, and evidence for the intended use all matter.
When categories combine: EEG-timed TMS, for example, uses a measurement to help time stimulation. Naming both parts is clearer than treating every brain technology as the same kind of intervention.
01NeurofeedbackFeedback about brain activity gives a person a way to practice self-regulation. EEG neurofeedback uses small scalp sensors to record electrical signals.
How it works
An amplifier makes the tiny signals readable. Software selects a feature, such as activity within a frequency band, and changes a sound or picture when the training criterion is met. Repeated feedback creates an opportunity for learning. In conventional EEG neurofeedback, the recording sensors do not deliver electricity to the brain.
What a session may involve
You sit with sensors or a cap while watching or listening to feedback. A provider checks signal quality and adjusts the session. You do not need to understand the EEG trace or consciously control each brainwave. Visits also include preparation and discussion, so appointment length is different from training time.
Making sense of the evidence
The intended change is better functioning outside the session. Track agreed goals, such as sleep or attention, alongside signal learning. Evidence varies by protocol and condition. Improvement on a screen alone cannot establish benefit. Report headache, fatigue, irritability or sleep changes so the provider can reassess the plan.
A question to bring
What signal are we training, why was it selected, and how will we decide whether it helps me?
02EEG and QEEGEEG records electrical activity from the scalp. QEEG, or quantitative EEG, uses calculations to describe patterns within that recording.
How it works
Software can summarize the strength of different rhythms or relationships between recording sites. Some reports compare these measures with a reference population. A colored map is a statistical display. It is not a photograph of the brain, and a color by itself is not a diagnosis.
What a session may involve
A provider places sensors, often in a cap, checks contact quality and records under specified conditions, such as eyes open or closed. Eye movements, jaw tension and movement can contaminate the signal and must be identified before interpretation.
FROM RECORDING TO INTERPRETATION
How a QEEG becomes part of a clinical conversation.
- 01
Record under defined conditions
Sensors capture scalp EEG while the person follows instructions such as resting with eyes open or closed.
- 02
Check the signal
Eye movement, jaw tension, loose contacts and other artifacts must be identified before calculations are trusted.
- 03
Summarize selected features
Software can calculate rhythm strength, timing or relationships between recording sites.
- 04
Compare when appropriate
Some reports compare selected measures with a reference population. The database and recording method matter.
- 05
Interpret in context
The recording is considered alongside history, symptoms, other assessments and the question that prompted the test.
A color map is a statistical summary, not a photograph or diagnosis. A useful interpretation depends on recording quality, suitable comparisons and the person’s broader clinical picture.
Making sense of the evidence
Ask about recording conditions, reference choice, artifact handling and the comparison database. Medication, sleep and alertness can affect interpretation. A 19-channel assessment samples multiple scalp locations, but its usefulness depends on a sound recording and a clinically appropriate question.
A question to bring
How does this report fit with my history and assessment, and what will it change about the plan?
032, 4 and 19-channel trainingChannel count describes how many EEG signal channels a system can process simultaneously. It does not tell you how effective a treatment will be.
How it works
A small-channel protocol may focus on selected scalp locations. A larger array can support broader measurements or calculations across sites. The number of recording channels, the number of sensors and the number of features used for feedback are different specifications.
What a session may involve
Setup may involve individual leads or a cap. More recording sites can mean more contact checks and more signals for the provider to inspect. A 19-channel QEEG assessment does not necessarily mean every training session uses 19 channels.
FROM RECORDING SCOPE TO FEEDBACK CHOICE
What channel count changes, and what it does not.
- 01
Name what is recorded
Channel count describes how many EEG signals can be processed at the same time. Sensors, recording locations and feedback features are separate specifications.
- 02
Check every signal
Each added recording site brings another contact and signal to inspect for movement, muscle activity and other artifacts.
- 03
Choose what drives feedback
A provider may use only selected channels or features for training. A 19-channel assessment does not mean all 19 channels are trained.
- 04
Match scope to the question
More channels can support broader measurement and calculations, but they do not by themselves establish a better clinical result.
More channels can add information and setup work, not automatic effectiveness. The number of sensors, processed channels and features used for feedback are related but different.
Making sense of the evidence
Choose an approach around the assessment question, signal quality and supporting evidence. ISNR encourages newcomers to develop competence in simpler power-training methods before progressing to more complex approaches. More channels do not establish superiority for an individual patient.
A question to bring
How many channels are recorded and actually used for feedback, and why is that appropriate for my goals?
04Z-score and Live Z-ScoreA Z-score describes how far a measurement sits from a reference average, expressed in standard-deviation units. Live Z-Score uses such comparisons during feedback.
How it works
Software repeatedly compares selected EEG features with a normative database. Feedback responds to the criteria chosen by the practitioner. This differs from rewarding a fixed amount of activity in one frequency band. The database, age matching and selected measures all matter.
What a session may involve
The experience may look much like other neurofeedback: sensors, sound or visual feedback, and repeated practice. Ask the provider to explain what the comparison means in ordinary language.
FROM REFERENCE TO FEEDBACK
How a Z-score comparison can shape a feedback rule.
- 01
Choose the measures and reference
The provider identifies selected EEG features and an appropriate age-matched reference database.
- 02
Calculate the comparison
Software expresses how far each selected measure sits from the reference average in standard-deviation units.
- 03
Set the feedback rule
The practitioner chooses which measures and thresholds affect the sound, image or other feedback cue.
- 04
Practice and review daily-life goals
Training is considered alongside symptoms, functioning, tolerability and goals that matter away from the screen.
A Z-score is a comparison, not a diagnosis or a universal treatment target. Movement toward the reference average does not by itself establish better health or daily functioning.
Making sense of the evidence
A reference average is not a universal treatment target. Movement toward it does not automatically establish improved health. The library includes a randomized trial with some favorable comparisons and mixed overall results, making symptom and functional tracking essential.
A question to bring
Which database and EEG measures are used, and how do we connect the target to an outcome that matters to me?
Explore the sourcesLink to this explanation
05sLORETA, eLORETA and swLORETAThese names refer to methods that estimate where electrical activity may originate, using signals measured at the scalp and a mathematical model.
How it works
Source estimation works backward from scalp measurements to a possible distribution of activity within the brain. Source-based neurofeedback can use a selected estimated region or relationship between regions for feedback. The result depends on the model and quality of the recording.
What a session may involve
A multi-sensor recording supplies the model. You may see ordinary audiovisual feedback rather than the source map. The clinician selects the estimated feature to train and monitors the recording for contamination.
FROM SCALP SIGNALS TO AN ESTIMATE
How LORETA methods support source-based feedback.
- 01
Record across the scalp
A multi-sensor EEG captures electrical activity at the scalp under defined recording conditions.
- 02
Check recording quality
The provider reviews contacts, movement, muscle activity and other artifacts before modeling the signal.
- 03
Apply a named source model
sLORETA, eLORETA or swLORETA uses mathematical assumptions to estimate a possible distribution of activity.
- 04
Use an estimated feature for feedback
A selected source estimate or relationship may guide ordinary audiovisual feedback during practice.
A source map is a model-based estimate, not a direct measurement from inside the brain. sLORETA, eLORETA and swLORETA are related but not interchangeable, and source-based training is not automatically superior.
Making sense of the evidence
The methods are related but not interchangeable. A detailed-looking map is still an estimate, not direct measurement from inside the brain. A study comparing sLORETA with conventional neurofeedback for tinnitus did not establish superiority of source-based training.
A question to bring
Which source method is used, what does it estimate, and what evidence supports this particular training target?
06ISF and ILF neurofeedbackInfra-slow fluctuation (ISF) and infra-low frequency (ILF) approaches work with very slow signal changes. The labels cover distinct methods and should not be treated as one standardized protocol.
How it works
A compatible recording system and software process slow activity to drive feedback. Providers may individualize the training parameters and sensor placement. The proposed links between slow activity, regulation and symptoms remain an active area of study.
What a session may involve
Feedback may be visual or auditory, and the provider asks about your response during and between visits. Ask how the system handles slow drift and other recording artifacts.
FROM SLOW SIGNAL TO FEEDBACK
How ISF and ILF methods turn slow activity into a training cue.
- 01
Record very slow activity
The system follows slow signal changes while the person sits or practices under the provider’s chosen recording conditions.
- 02
Check drift and artifact
Movement, contact changes and other slow drift can resemble the activity of interest, so signal quality needs ongoing attention.
- 03
Apply the named method
ISF and ILF labels describe related slow-frequency approaches, but software, processing and feedback rules can differ by protocol.
- 04
Review the person’s response
The provider adjusts the plan using tolerability, sleep, symptoms and daily-life functioning rather than a universal ideal frequency.
ISF and ILF are not automatically interchangeable protocols. Very slow signals are sensitive to drift and artifact, and one method or study population does not establish benefit across every approach.
Making sense of the evidence
Evidence is protocol-specific. The library includes promising clinical observations and a placebo-controlled healthy-adult ILF trial that found no significant advantage on tested outcomes. A result from one method or population should not be transferred to every ISF or ILF system.
A question to bring
Which exact ISF or ILF method is this, what is measured, and how will changes or unwanted effects be tracked?
07Event-related potentials (ERP)An ERP is a pattern in EEG activity measured in relation to an event, such as a tone or picture. It helps researchers examine the timing of a response.
How it works
The same kind of event is presented repeatedly. EEG segments are aligned to the event and commonly averaged to make small responses easier to detect. Names such as P300 describe a waveform feature, not a diagnosis.
What a session may involve
You may listen to tones, watch images or respond to selected events while wearing EEG sensors. The task instructions, hearing or vision, attention and number of usable trials can all affect the result.
FROM EVENT TIMING TO AN AVERAGED RESPONSE
How repeated events become an ERP.
- 01
Define the event and task
The protocol specifies a tone, picture or other event, what the person should do and the response the test is designed to examine.
- 02
Record repeated trials
EEG is recorded while the event occurs many times, with timing markers that connect each segment to the event.
- 03
Review usable segments
Eye movement, muscle activity, missed events and other contamination are considered before the selected trials are combined.
- 04
Align and average
Valid EEG segments are aligned to the event and commonly averaged so a small time-locked response can be easier to detect.
- 05
Interpret in task context
Features such as timing or amplitude are considered with the task, recording method, sensory factors, attention and usable trial count.
An ERP is a time-locked average, not a diagnosis or measure of intelligence. Its timing and size depend on the task, recording quality, sensory factors, attention and the number of usable trials.
Making sense of the evidence
ERP assessment is different from neurofeedback training. Its interpretation depends on the task and recording methods. A delayed or smaller response needs context; it cannot by itself explain a person’s symptoms or establish intelligence.
A question to bring
What task and response are being measured, and what question can this test reliably answer?
08Biofeedback and HRVBiofeedback makes a body signal visible or audible so you can practice responding to it. Signals can include muscle tension, skin temperature or heart rhythm.
How it works
Heart rate variability, or HRV, concerns changes in timing between heartbeats. HRV biofeedback uses measured heart-rate patterns alongside breathing practice. A provider helps you observe how the pattern changes; the aim is not simply to make the heart beat as slowly as possible.
What a session may involve
A sensor records the heart signal while you follow comfortable breathing guidance. The session may include practice with and without feedback. Muscle biofeedback instead uses sensors to help identify patterns of tension and relaxation.
A PRACTICE LOOP
What happens during HRV biofeedback practice.
- 01
Measure beat-to-beat timing
A sensor records the changing intervals between heartbeats and checks whether the signal is usable.
- 02
Use comfortable breathing guidance
The person follows a paced breathing cue without forcing a very slow or uncomfortable pattern.
- 03
Watch the live response
Feedback shows how the measured heart-rate pattern changes during practice.
- 04
Review and practice away from the screen
The provider connects the exercise with agreed goals and a practical plan for between-session practice.
The goal is not simply to make the heart beat as slowly as possible. HRV biofeedback pairs a measured signal with comfortable practice and outcomes that matter outside the session.
Making sense of the evidence
A consumer readiness score is not interchangeable with a transparent HRV measurement. Signal quality, measurement conditions and the intended outcome matter. Research on stress and anxiety is promising, but findings do not apply automatically to every device or condition.
A question to bring
Which body signal are we measuring, how is it calculated, and what should I practice between visits?
Explore the sourcesLink to this explanation
09Photobiomodulation (PBM)PBM uses red or near-infrared light from LEDs or lasers. Transcranial PBM applies light to the head with the aim of influencing underlying tissue.
How it works
Researchers study how absorbed light may affect cellular energy processes, including mitochondrial activity, and related blood-flow and signaling pathways. These are proposed mechanisms whose relevance depends on the exposure and tissue. A biological mechanism alone does not demonstrate a clinical benefit.
What a session may involve
A device delivers light for a specified period. Wavelength, intensity, exposure time, pulsing and placement all affect the exposure. Use the device-specific eye-protection and operating instructions; visible brightness does not tell you the dose reaching the brain.
FROM DEVICE DETAILS TO RELEVANT EVIDENCE
What defines a photobiomodulation protocol.
- 01
Identify the light source
Record the wavelength, delivery type and output specified for the device rather than relying on color or brightness alone.
- 02
Define the exposure
Placement, treated area, session time, pulsing and distance all help define the protocol being delivered.
- 03
Follow device-specific safety
Use the operating instructions, eye protection and contraindication guidance for that exact device and application.
- 04
Match evidence to the protocol
Compare human studies using a similar device, dose, placement, population and outcome instead of generalizing across all red-light products.
A wavelength or flashing rate does not define the full exposure. Placement, output, area, time, pulsing and device design matter, and a proposed cellular mechanism does not by itself establish clinical benefit.
Making sense of the evidence
Only part of the applied light reaches deeper tissue. Results from one light device, body location or study cannot be transferred to every red-light product. Ask about human clinical outcomes as well as laboratory mechanisms, and keep emerging brain applications distinct from established uses elsewhere.
A question to bring
What wavelength and dose are used, and which human study tested a comparable device, protocol and population?
10TMS and rTMSTranscranial magnetic stimulation uses a coil near the scalp to create changing magnetic fields that induce electrical activity in brain tissue. rTMS delivers repeated pulses.
How it works
The stimulation pattern, target and intensity influence the intervention. Theta-burst stimulation is one patterned form. Unlike feedback training, TMS applies a physical stimulus directly; some research systems use EEG to help time that stimulus.
What a session may involve
You remain awake while a trained team positions the coil and delivers pulses. You may hear clicking and feel tapping or scalp discomfort. Screening includes relevant medical history, seizure risk and implanted devices; hearing protection is used.
FROM SCREENING TO REVIEW
How a TMS treatment plan becomes a monitored session.
- 01
Confirm the intended use
Name the condition, device and protocol, then separate an authorized use from an experimental target or schedule.
- 02
Complete safety screening
Review seizure risk, relevant medical history, medications and implanted or metallic devices before stimulation.
- 03
Set the stimulation plan
The trained team selects the target, intensity, pulse pattern and session schedule for the proposed use.
- 04
Monitor each session
The person remains awake, uses hearing protection and reports tapping, discomfort, headache or other effects.
- 05
Review benefit and tolerability
Track agreed clinical and daily-life outcomes alongside adverse effects, attendance and reasons to reconsider the plan.
TMS is stimulation, not feedback training. Authorization applies to specific devices and uses, while target, pulse pattern, screening and follow-up remain part of the clinical plan.
Making sense of the evidence
Some TMS devices have authorization for specific clinical uses. That does not authorize every target or protocol. Common effects can include headache or scalp discomfort; seizures are uncommon but a recognized risk. Device instructions and clinical screening govern use.
A question to bring
Which device and protocol are proposed, what is its authorization for this use, and how will benefit and tolerability be assessed?
Explore the sourcesLink to this explanation
11Pulsed electromagnetic fields (PEMF)PEMF devices generate magnetic fields that change over time. The name covers a wide range of devices, field strengths, pulse shapes and intended applications.
How it works
A changing magnetic field can induce electrical effects in tissue. Exposure depends on the field, pulse pattern, coil geometry and distance. A label such as “10 Hz” describes repetition frequency and is not enough to compare two devices.
What a session may involve
An applicator may be positioned near a selected body area. Duration and use instructions vary by device. Inform the provider about implanted electronic devices and follow the manufacturer’s contraindications.
FROM DEVICE DETAILS TO RELEVANT EVIDENCE
What makes one magnetic-field protocol different from another.
- 01
Identify the exact system
Name the device, intended application and whether it delivers pulsed magnetic fields, TMS or a static magnetic field.
- 02
Define the exposure
Field strength, pulse shape, repetition pattern, coil or applicator, distance and placement all help define what is delivered.
- 03
Screen for device-specific risks
Follow the manufacturer’s instructions and review implants, medical conditions and other contraindications for that exact system.
- 04
Match the evidence
Look for research using a comparable device, dose, target, population and outcome instead of generalizing across magnetic products.
A frequency such as 10 Hz does not define the full exposure. PEMF is a broad device class, is not the same as TMS or a static magnet, and evidence for one application does not validate every magnetic product.
Making sense of the evidence
PEMF and TMS should not be treated as equivalent treatments. Evidence for a bone-healing or pain application does not establish a brain-health benefit. Static magnets also differ from pulsed systems. The research library includes a specific depression study, not a class-wide endorsement.
A question to bring
What exact field and waveform reach the target, and is there evidence for this device and intended use?
More guides & practical tools
Neurofeedback / Guide
Neurofeedback for beginners: a clear, practical guide
Understand what EEG neurofeedback measures, what a first visit may involve, how to read the evidence, and how to choose and review care.
Biofeedback / Guide
Biofeedback beyond the brainwave
Meet the wider landscape of physiological feedback, including heart rate variability.
Magnetic stimulation & PEMF / Guide
Magnetic stimulation: the questions that matter
A field guide to reading device descriptions without treating every magnetic technology as interchangeable.
QEEG / Toolkit
Before a QEEG: build a better conversation
A practical checklist for discussing recording quality, interpretation, and next steps with your provider.
Brain health / Toolkit
Build a better brain health technology shortlist
A repeatable framework for comparing tools, services, and the questions behind the claims.
A PRACTICAL TOOL
Your provider conversation checklist
Prepare for a useful first conversation.
0 of 6 discussion points prepared. Selections stay on this page only.
FOLLOW THE SOURCE
Keep learning.
Primary references for your next question.
History of EEG & neurofeedback: meet the pioneers BCIA: neurofeedback education & certification NIMH: brain stimulation therapies PubMed: explore the published research NCCIH: relaxation & biofeedback
Educational resources here do not confer certification or continuing education credit.