Technical Foundations of Neurofeedback

Thomas F. Collura

• Publisher: Routledge
• Year: 2014
• ISBN:
  9781134467488
• Edition: 1
• Topic: Psychologie
• Subtopic: Neuropsychologie

Technical Foundations of Neurofeedback provides, for the first time, an authoritative and complete account of the scientific and technical basis of EEG biofeedback. Beginning with the physiological origins of EEG rhythms, Collura describes the basis of measuring brain activity from the scalp and how brain rhythms reflect key brain regulatory processes. He then develops the theory as well as the practice of measuring, processing, and feeding back brain activity information for biofeedback training. Combining both a "top down" and a "bottom up" approach, Collura describes the core scientific principles, as well as current clinical experience and practical aspects of neurofeedback assessment and treatment therapy. Whether the reader has a technical need to understand neurofeedback, is a current or future neurofeedback practitioner, or only wants to understand the scientific basis of this important new field, this concise and authoritative book will be a key source of information.

.

1 OVERVIEW

DOI: 10.4324/9780203795132-1

Definition of Neurofeedback

Neurofeedback is a form of biofeedback training that uses the EEG (electroencephalogram), also known as the “brainwave,” as the signal used to control feedback. Sensors applied to the trainee’s scalp record the brainwaves, which are converted into feedback signals by a human/machine interface using a computer and software. By using visual, sound, or tactile feedback to produce learning in the brain, its primary use has been to improve brain relaxation through increasing alpha waves or related rhythms. A variety of additional benefits, derived from the improved ability of the CNS (central nervous system) to modulate the concentration/relaxation cycle and brain connectivity, may also be obtained.

In summary, neurofeedback consists of the following key elements:

• production of the EEG by the brain;
• recording of the EEG using suitable instrumentation;
• digitizing of the EEG into computer form;
• computation of EEG characteristics (signal processing);
• production and presentation of feedback (visual, auditory, tactile, etc.); and
• resulting learning by the brain, leading to physiological change.

This book will describe each of these processes in detail, and will thus encompass the areas of neurophysiology, biomedical engineering, digital signal processing, computer technology, and clinical therapeutics. In this chapter, we will provide an overview of the above concepts and present an integrated view of the process of neurofeedback.

It is important at the outset to distinguish neurofeedback from conventional EEG, and also from quantitative EEG (QEEG). Although these areas are related, they are by no means the same. Electroencephalography (EEG) is a technique by which the brain’s electrical activity is recorded by the use of sensors placed on the scalp, and sensitive amplifiers. The EEG was first recorded by the German psychiatrist Hans Berger in 1932, and has become an accepted clinical tool for neurologists and psychiatrists. Generally, EEG is analyzed by visually inspecting the waveforms, often using a variety of montages. Neurologists are able to identify abnormalities, including epilepsy, head injuries, stroke, and other disease conditions, using the EEG. A clinical EEG practitioner in the medical profession must first be a neurologist or psychiatrist and complete an additional two-year residency and board certification in clinical neurophysiology, sleep disorders, epilepsy, or a related field to be eligible to read and interpret clinical EEGs.

Quantitative EEG (QEEG) is a technique in which EEG recordings are computer-analyzed to produce numbers referred to as “metrics” (e.g. amplitude or power, ratios, coherence, phase, etc.) used to guide decision-making and therapeutic planning. QEEG can also be used to monitor and assess treatment progress. QEEG data typically consist of raw numbers, statistics generally in the form of z-scores, and/or topographic or connectivity maps. QEEG systems currently lack strong standardization, and a wide range of methods and achievable results exist in the field. Although QEEG uses computer software to produce results, an understanding of basic EEG, and the ability to read and understand raw EEG waveforms, is required in order to competently practice QEEG. Generally, a specialist (e.g. a board-certified MD, PhD, QEEG-T, or QEEG-D) is consulted to read and interpret QEEG data and produce reports and treatment recommendations, unless the practitioner has appropriate experience and credentials.

Despite the fact that EEG, QEEG, and neurofeedback all make use of the same signal, they are based upon different sets of assumptions and clinical purposes. It turns out that a good understanding of both conventional EEG and of QEEG is important for the effective use of neurofeedback. In particular, in the areas of assessment and progress monitoring, a grasp of what a clinical neurophysiologist would think of the EEG, as well as what a QEEG practitioner would see, are both helpful in planning and evaluating neurofeedback interventions.

In contrast to clinical EEG and QEEG, neurofeedback can be ethically practiced by a wide range of practitioners with various backgrounds. Neurofeedback is not a “quick cure” or a “one-size-fits-all” intervention guaranteed to fix all ills. Rather, it is an evidence-based adjunctive to existing forms of treatment, and can be used by any practitioner who has reasonable training and is working within his or her own individual scope of practice. Therefore, psychologists, counselors, social workers, occupational therapists, language therapists, educators, and other professionals can incorporate neurofeedback into their work, or refer clients to neurofeedback therapists. Neurofeedback is best used when it takes advantage of brain plasticity to support and reinforce clinical goals in a manner consistent with evidence-based practice. In this regard, neurofeedback is on a par with other interventions such as psychotherapy, eye movement desensitization and reprocessing (EMDR), hypnotherapy, cognitive-behavioral therapy, and a host of other interventions targeting brain plasticity and change. While there are various certifications available for neurofeedback practitioners, there is no strict educational or licensing requirement; practitioners must first and foremost work within their licensure and competence, and add neurofeedback as appropriate.

Figure 1.1 shows a conceptual view of neurofeedback. We focus our attention in this analysis on brain events that represent specific patterns of neuronal activity. Some of these events are internalized in the form of thoughts that are perceived only by the individual as part of his or her internal world. Other brain events lead to external behaviors that are observed by others and also become part of the environment of the individual and are perceived as his or her own behavior. The normal pattern of brain activity is limited to this restricted space of awareness. The best that a clinician can do with regard to brain activity is to use a talk or experiential/behavioral technique to alter the client’s internal processing, or to use medications or stimulators to alter its function directly.

Figure 1.1 A conceptual view of neurofeedback as a component in the client’s overall environment.

Table 1.1 presents a summary view of four of the major modalities available to the mental health practitioner. For each method, we look at whether it is based on learning, or on altering the brain, whether it has a strong biological basis. Specificity refers to whether the method can target specific brain locations or processes. Directedness indicates whether the intervention can be steered or directed, or is simply administered the same way for all clients. While there is room for opinion in this analysis, the general conclusion is that neurofeedback has the potential to be unique as a learning technique that is noninvasive yet biologically based, with high specificity and directedness in its ability to influence brain function.

Summary of Major Mental Health Interventions and their Properties

Neurofeedback introduces an entirely new facet to the experience of the brain events. With neurofeedback, an individual becomes aware of certain of his or her own brain events, and these then enter consciousness in the form of the neurofeedback experience. This is more than a mere therapeutic trick. It introduces an element of voluntary, as well as involuntary, control to critical aspects that have been hidden and now become part of the client’s decision-making repertoire. As we shall see, neurofeedback can be configured in many different ways, so that the external manifestation of brain activity that appears in the computer display provides the potential for change. It is as if someone who had never seen a mirror was suddenly able to see himself or herself, and to modify his or her behavior and appearance based upon this new information.

Table 1.1 Options for mental health interventions

Modality	Method	Invasive	Biological basis	Specificity	Directedness
Talk/behavioral Therapy	Learning (various)	No	Moderate (when neuroscience-driven)	Moderate (cognitive/emotional)	High (can focus on issue or problem)
Pharmaceutical	Altering (chemistry)	Yes	High (chemical change)	Moderate (neurotrans-mitters)	Low (widely distributed in brain, side effects and abreactions can occur)
Stimulation	Altering (electrical)	Yes	High (electrical conduction)	Moderate (location on head)	Moderate (polarity, location)
Neurofeedback	Learning (operant)	No	High (EEG and learning process)	High (site-specific or LORETA)	High (wide range of protocols, settings, sites)

Figure 1.2 shows the simplest possible block diagram of a computerized neurofeedback system. Essentially, all contemporary neurofeedback devices operate according to this plan. Significant differences exist between implementations relating to the details of the amplifier, computer software, display, etc. However, this basic approach is a common factor, regardless of the system designer or manner of use.

Figure 1.3 shows one possible embodiment of neurofeedback, in which two participants are provided with information in the form of the movement of toy cars on a track. As the participants achieve the target set of brainwave condition, their cars move faster, thus providing a simple and intuitive form of feedback.

Figure 1.2 Conceptual block diagram of neurofeedback with client.

Figure 1.3 Two boys playing brain-controlled race cars as a form of neurofeedback.

Source: Photo courtesy of Dr. Doerte Klein

The following section provides, in a single narrative, the end-to-end picture of neurofeedback as it is viewed from a technical point of view.

Generation of the EEG

Pyramidal Cells in the Cerebral Cortex Produce Electrical Potentials

The EEG is a bioelectric potential that is recorded from the surface of the head, using appropriate electrodes and instrumentation. The human EEG was first recorded by Hans Berger in 1929, and within the following 10 years, all of the common brain rhythms had been observed and named, including delta, theta, alpha and beta waves. Measurable surface potentials (microvoltages) are produced by brain cells (neurons) in the upper layers of the cerebral cortex, which contains the outer information-processing layers of the brain, and which underlies essentially the entire scalp. The predominant EEG signals are produced by giant pyramidal cells, which are populous in layers II and IV, and are often oriented in a manner that encourages the production of measurable potentials. The cerebral cortex is divided into areas designated the frontal, parietal, occipital, and temporal lobes.

Based on the underlying physics, we understand that brain electrical sources are dipoles. An electrical dipole is a charged entity that has a positive “plus” side and an opposing negative “minus” side. For example, a battery immersed in a bath of salt water provides a good model of a dipole residing in a conducting medium. If electrodes are placed in the water bath, it is possible to measure the potential difference between any pair of points, thus measuring the voltage that would be analogous to an EEG measurement using two electrodes.

It is important to make two distinctions clear. The first is that the EEG is not there for any physiological reason, and does not reflect the brain’s business in any direct sense. It is rather an “epiphenomenon” not unlike the heat coming from your computer, or the vibration on the hood of your car. It is a useful indicator of some aspects of brain function, but it is not a direct measure of information processing, such as a recording of action potentials might be. Second, even as it is detected, the EEG is not the “activity” of the brain. Rather, as shall be explained, the presence of a rhythm typically indicates that a region is idle and is in a neutral state. However, it may also indicate that region is “offline,” or that it is “disconnected” from other regions. As tempting as it might be to make a value judgment that “large is good” or “smooth is better,” no such simple distinctions can be made in EEG. As shall be explained, the bad news is that the neurofeedback practitioner really needs to learn a lot about the brain, how it works, and how EEG is generated. The good news is that all of this information is relevant, and neurofeedback is in fact a strongly evidence-based, brain-based therapeutic approach with extremely solid scientific foundations. In some cases, our understanding of neurofeedback is equal to, or superior to, our understanding of psychoactive medications, if one takes the time to look at the evidence.

EEG Amplitude Reflects Local Synchrony

Measurable EEG signals occur only when a population of cortical cells is excited (depolarized) in unison, providing a “consensus” potential, which is the sum of many small electrical potentials. If the cells behave independently, as they do when in an excited, active state, then the potential as viewed from the scalp are very small, due to the cancellation. Note that the measured potentials are actually epiphenomena, and are a byproduct of the normal activity of the brain. For example, consider the vibrations that can be sensed from the hood of a car. These are byproducts that can be used to diagnose and understand what is happening inside the car, but these are not fundamental to how the engine works.

Measured Rhythms Reflect Modulation in Activation and Inhibition

As a result of the previous considerations, it can be seen that the presence of a measurable EEG potential at any frequency reflects a measurable rhythm associated with local synchrony. Paradoxically, such synchrony may reflect the fact that a population of cells is actually not involved in active information processing, but is in an idling state. Many brain rhythms, in particular the alpha rhythm, are mediated by thalamo-cortical mechanisms that lead to the rhythmic interaction of different brain locations. In the course of its normal activity, the brain puts particular brain areas into a state of relative activation, or deactivation (inhibition). It is the modulation of these states that produces the characteristic waxing and waning that is visible ...