Assessment Demonstration

Overview


We have discussed the assessment of the EEG from a variety of perspectives in other sections of Neurofeedback Tutor. This section will provide examples of relatively simple and more complex EEG assessment approaches.

Dr. Ronald Swatzyna has generously permitted the authors to share the Houston Neuroscience Brain Center's client qEEG cap orientation video.





As noted previously, EEG assessment begins with a visual inspection of the EEG recording, using various montages (sensor comparisons) to identify the EEG's basic characteristics and determine whether there are abnormal patterns that warrant a referral for a neurological consultation. Following this inspection, a quantitative analysis may be desired, and this section will demonstrate some examples.

Neurofeedback Tutor describes and demonstrates an example of a 2-channel assessment that uses a series of three pairs of 10-20 sites, with specific tasks for each pair. This should not be confused with an EEG assessment that uses two channels at only two assessment sites, which likely would have limited usefulness because any particular clinical complaint may be associated with deviation from the expected range at different locations depending on the individual.

Since Neurofeedback Tutor is equipment, software, and database agnostic, we will illustrate this unit with products from several manufacturers.

BCIA Blueprint Coverage


This unit covers VI. Patient/Client Assessment - D. Assessment Demonstration: Perform a basic EEG assessment, an abbreviated Q recording and/or attaching electrode cap and completing an abbreviated Q or 19-channel QEEG recording.




This unit covers abbreviated Q and 19-channel recordings.

Please click on the podcast icon below to hear a full-length lecture.





ABBREVIATED Q RECORDINGS



NewQ

The first example is the NewQ, a six-location assessment similar to various other assessments that use a subset of the 19 scalp locations (10-20 system of electrode placement) to produce a somewhat limited but often helpful analysis of client findings.

EEG assessments similar to the NewQ include New Mind Maps, The Learning Curve (TLC), the Clinical Q, and others. Some are designed for specific hardware/software platforms, and some can be used with multiple systems. As a class, they offer the clinician a degree of automation in collecting, processing, and interpreting EEG information that allows beginners and experienced practitioners alike to use expert systems that will ideally improve the assessment process. One commonality with these approaches is using a “Clinical Database” (Swingle, 2014).

Swingle states that clinical databases are superior to normative databases because they are related to clinical findings and variations of results compared to known values such as the typical voltage of alpha activity in a particular region and associated with specific tasks. The development of a clinical database follows the developer's experience and allows other practitioners to benefit from that developer's years of education, training, and experience. The use of a clinical database does not result in a formal diagnosis like that seen in the Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5). Instead, the clinical database assessment suggests possible clinically relevant findings related to the client’s symptoms.

For example, a lack of a typical increase in amplitude (voltage) of 8-12 Hz activity in occipital and parietal areas of the scalp may relate to a variety of symptoms such as anxiety, post-traumatic stress disorder (PTSD), perseveration, rumination, hypervigilance, or other findings. It may be associated with difficulty sleeping, self-calming, physiological exhaustion, and other issues. Once the clinician has this information, they can decide what training protocol may be most helpful for that client. The assessment can also be repeated quite easily to track progress and identify additional training approaches.

The following video describes the NewQ as an example of such an assessment. Next, a video demonstrates collecting the data, processing the data, and interpreting the findings. The video shows only one of the available assessment tools, but it is somewhat representative of them all. Some identify more sites, and some collect the data all at once. Some use individual sensors and an EEG “cap” or array of EEG sensors in mesh material, as seen in the images below.

 



Video © J. S. Anderson.



Abbreviated Q assessments can provide useful information about the client, help validate and explain client symptoms and assist with training protocol selection. Two other report examples are seen below:







Clinical Q Assessment Report



19-CHANNEL RECORDINGS


The primary alternative to these assessments is the full 19-channel recording with a normative database comparison. The following video will demonstrate such a recording process. Subsequent videos will give an overview of the much more extensive and involved artifact rejection process while providing an example of a visual inspection of the EEG using various montages and show the results of such an assessment in the form of tables and topographic maps. Finally, we will explore various training approaches with video examples. Video © J. S. Anderson.




EEG Recording, Testing, and Protocol Development

We encourage you to view the next two-hour video in stages. This recording provides a comprehensive overview of assessment, protocol selection, treatment, and qEEG-guided neurofeedback. Video © J. S. Anderson.




Clean Data Extraction and Comparison to a Normative Database

Visual inspection begins with recording 19 EEG channels with the standard configuration of 19 scalp sensors referenced to linked ears compared with a normative database. The following video shows the examination of the original recording, extraction of sections for each recording condition (e.g., eyes open and closed), visual inspection using multiple montages, selection of clean, artifact-free data, and translation of that data into comparisons with the normative database. Video © J. S. Anderson.

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Glossary


A (auricular): International 10-20 system earlobe reference placement.

alpha rhythm: 8-12-Hz activity that depends on the interaction between rhythmic burst firing by a subset of thalamocortical (TC) neurons linked by gap junctions and rhythmic inhibition by widely distributed reticular nucleus neurons. Researchers have correlated the alpha rhythm with relaxed wakefulness. Alpha is the dominant rhythm in adults and is located posteriorly. The alpha rhythm may be divided into alpha 1 (8-10 Hz) and alpha 2 (10-12 Hz).

amplitude: the strength of the EEG signal measured in microvolt or picowatts.

artifact: false signals like 50/60Hz noise produced by line current.

beta rhythm: 12-38-Hz activity associated with arousal and attention generated by brainstem mesencephalic reticular stimulation that depolarizes neurons in the thalamus and cortex. The beta rhythm can be divided into multiple ranges: beta 1 (12-15 Hz), beta 2 (15-18 Hz), beta 3 (18-25 Hz), and beta 4 (25-38 Hz).

bipolar (sequential) montage: a recording method that uses two active electrodes and a common reference.

bridging artifact: a short circuit between adjacent electrodes due to excessive application of electrode paste or a client sweating excessively or arrives with a wet scalp.

C (central): sites in the International 10-20 system that detect frontal, parietal-occipital, and temporal EEG activity.

channel: EEG amplifier input from three leads (active, reference, and ground electrodes) placed on the head.

clinical database: qEEG metrics obtained from a representative sample of participants during resting and active-task conditions related to clinical findings.

delta rhythm: 0.05-3 Hz oscillations generated by thalamocortical neurons during stage 3 sleep.

drowsiness artifact: in adults, 1-Hz (or slower) waveforms can be detected with the greatest amplitude, and reverse polarity at F7 and F8 may progress to 1-2 Hz slowing of the alpha rhythm.

EEG artifacts: noncerebral electrical activity in an EEG recording can be divided into physiological and exogenous artifacts.

electro-ocular artifact: contamination of EEG recordings by potentials generated by eye blinks, eye flutter, and eye movements.

electrode pop artifact: sudden large deflections in at least one channel when an electrode abruptly detaches from the scalp.

EMG artifact: interference in EEG recording by volume-conducted signals from skeletal muscles.

exogenous artifacts: noncerebral electrical activity generated by movement, 50/60 Hz and field effect, bridging, and electrode (electrode “pop" and impedance) artifacts.

F (frontal): sites in the International 10-20 system that detect frontal lobe EEG activity.

Fp (frontopolar or prefrontal): sites in the International 10-20 system that detect prefrontal cortical EEG activity.

hertz (Hz): a unit of frequency measured in cycles per second.

impedance (Z): the complex opposition to an AC signal measured in Kohms.

impedance meter: a device that uses an AC signal to measure impedance in an electric circuit, such as between active and reference electrodes.

impedance test: automated or manual measurement of skin-electrode impedance.

inion: a bony prominence on the back of the skull.

International 10-20 system: a standardized procedure for 21 recording and one ground electrode on adults.

low resolution electromagnetic tomography (LORETA): Pascual-Marqui's (1994) mathematical inverse solution to identify the cortical sources of 19-electrode quantitative data acquired from the scalp.

mastoid bone: bony prominence behind the ear.

microvolt (μV): a unit of amplitude (signal strength) that is one-millionth of a volt.

montage: a grouping of electrodes (combining derivations) to record EEG activity.

movement artifact: voltages caused by client movement or the movement of electrode wires by other individuals.

nasion: the depression at the bridge of the nose.

normative database: qEEG metrics obtained from a representative sample of participants during resting and active-task conditions.

notch filter: a filter that suppresses a narrow band of frequencies, such as those produced by line current at 50/60Hz.

O (occipital): sites in the International 10-20 system that detect occipital lobe EEG activity.

ohm (Ω): a unit of impedance or resistance.

P (parietal): sites in the International 10-20 system that detect parietal lobe EEG activity.

physiological artifacts: noncerebral electrical activity that includes electromyographic, electro-ocular (eye blink and eye movement), cardiac (pulse), sweat (skin impedance), drowsiness, and evoked potential.

posterior dominant rhythm (PDR): the highest-amplitude frequency detected at the posterior scalp when eyes are closed.

power: the amplitude squared and may be expressed as microvolts squared or picowatts/resistance.

preauricular point: the slight depression located in front of the ear and above the earlobe.

protocol: a rigorously organized plan for training.

pulse artifacts: noncerebral voltages due to mechanical movement of an electrode in relation to the skin surface due to the pressure wave of each heartbeat.

Quantitative EEG (qEEG): digitized statistical brain mapping using at least a 19-channel montage to measure EEG amplitude within specific frequency bins.

reference electrode: an electrode placed on the scalp, earlobe, or mastoid.

rhythmic temporal theta of drowsiness (RMTD): bitemporal left is greater than right in this longitudinal bipolar montage. Noted are notched rhythmic waveforms localized to the temporal regions, some of which are sharply contoured.

sensorimotor rhythm (SMR): the 13-15 Hz spindle-shaped sensorimotor rhythm (SMR) detected from the sensorimotor strip when individuals reduce attention to sensory input and reduce motor activity.

standardized LORETA (sLORETA): a refinement of LORETA that estimates each voxel's electrical potentials without regard to their frequency, expresses normalized F-values, and achieves a 1-cubic-cm resolution.

surface Laplacian (SL) analysis: a family of mathematical algorithms that provide two-dimensional images of radial current flow from cortical dipoles to the scalp.

swLORETA: a more precise and accurate iteration of the LORETA source localization method.

theta/beta ratio (T/B ratio): the ratio between 4-7 Hz theta and 13-21 Hz beta, measured most typically along the midline and generally in the anterior midline near the 10-20 system location Fz.

theta rhythm: 4-8-Hz rhythms generated a cholinergic septohippocampal system that receives input from the ascending reticular formation and a noncholinergic system that originates in the entorhinal cortex, which corresponds to Brodmann areas 28 and 34 at the caudal region of the temporal lobe.

z-score training: a neurofeedback protocol that reinforces in real-time closer approximations of client EEG values to those in a normative database.

tragus: the flap at the opening of the ear.

transient: isolated waveforms or complexes that can be distinguished from background activity.

vertex (Cz): the intersection of imaginary lines drawn from the nasion to inion and between the two preauricular points in the International 10-10 and 10-20 systems.


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Assignment


Now that you have completed this unit, explain why the visual inspection of raw EEG waveforms is important.

References


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Hardt, J. V., & Kamiya, J. (1978). Anxiety change through electroencephalographic alpha feedback seen only in high anxiety subjects. Science, 201(4350).79-81. https://doi.org/10.1126/science.663641 PMID: 663641.

John, E. R., Ahn, H., & Prichep, L., Trepetin, M., Brown, D., & Kaye, H. (1980). Developmental equations for the electroencephalogram. Science, 210(4475), 1255-1258. https://doi.org/10.1126/science.7434026

Johnstone, J. & Gunkelman, J. (2003). Use of databases in QEEG evaluation. Journal of Neurotherapy, 7, 3-4, 31-52. https://doi.org/10.1300/J184v07n03_02

Kamiya, J. (1968). Conscious control of brain waves. Psychology Today, 1, 56-60.

Nuwer, M. R., & Coutin-Churchman, P. (2014). Brain mapping and quantitative electroencephalogram. Encyclopedia of the Neurological Sciences (2nd ed.). Elsevier.

Rogala, J., Jurewicz, K., Paluch, K., Kublik, E., Cetnarski, R., & Wróbel, A. (2016). The do's and don'ts of neurofeedback training: A review of the controlled studies using healthy adults. Frontiers in Human Neuroscience, 10, 301. https://doi.org/10.3389/fnhum.2016.00301

Soutar, R., & Longo, R. (2022). Doing neurofeedback: An introduction (2nd ed.). ISNR Research Foundation.

Swingle, P. (2014). Clinical versus normative databases: Case studies of clinical Q assessments. NeuroConnections.

Thatcher, R. W. (1998). Normative EEG databases and EEG biofeedback. Journal of Neurotherapy, 2(4), 8-39. https://doi.org/10.1300/J184v02n04_02

Thatcher, R. W., Lubar, J. F., & Koberda, J. L. (2019). Z-Score EEG biofeedback: Past, present, and future. Biofeedback, 47(4), 89–103. https://doi.org/10.5298/1081-5937-47.4.04

Thomas, C. (2007). What is a montage? EEG instrumentation. American Society of Electroneurodiagnostic Technologists, Inc.

Thompson, M., & Thompson, L. (2015). Neurofeedback Book: An introduction to basic concepts in applied psychophysiology (2nd ed.). Association for the Advancement of Psychophysiology and Biofeedback.