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Background Reading / Media
What is Neurofeedback and How Does it Work?
In the 1950s neuroscientists developed equipment that allowed rats to stimulate the pleasure centers of the brain. A lever was connected to a weak electrical generator which itself was connected by a wire to the deepest part of the rat’s brain. Whenever a rat tapped the lever, a miniscule amount of electricity flowed from the generator into the rat’s brain, into the pleasure center of the brain. Rats wired in this fashion quickly caught on to the nature of the task and after little training would tap the lever thousands of times an hour to receive the impulse. The rodent wireheads would pass up sleep, comfort, food, and even a receptive mate to work the bar. It was found to be the strongest form of learning ever to occur on the planet, and extremely resistant to extinction, to use the terminology of the day. Most rats would indulge in day-long binges of self-stimulation without a moment’s rest and even when an electrified grid was placed between them and the lever, the rats would risk a gauntlet of shocks to gain access to their beloved.
The implications for studying addiction were obvious; the implications for learning and brain normalization training less so. But rats are rats. Would humans fare any better if allowed to reward themselves similarly, that is, intra-cranially without restraint?
What do you think? A few epileptic patients stimulated themselves into convulsions before the experiments were called off.
EEG operant conditioning does not stimulate the brain directly -- rewards come in through the eyes and ears and mind of the individual -- but by rewarding EEG changes with visual and auditory rewards a therapist is able to help shape an individual’s brainwave activity toward normal patterns of activity. The advent of powerful personal computers and advances in miniaturization and amplification has allowed anyone who doesn’t mind getting gel in their hair the ability to visualize the electrical activity of their own brain and once you can visualize your behavior, you can change it.
Brainwaves are minute electrical voltages generated by the top layer of the brain (cortex) which can be detected by modern electrical equipment. Sensors placed on the scalp record these tiny voltage changes across the scalp and analyze the signals looking for specific rhythms. When brain rhythms are normal, an individual is rewarded, usually by means of a sound (bell or chime) or light or video event. But when his or her brainwave activity deviates from normal, this positive feedback stops and a negative response may be provided such as a red flashing light or even a buzzer. In this fashion good brain-behaviors are exercised and undesirable brain-behaviors are not reinforced, with a goal being the accumulation of good brain-behaviors. A reasonably large repertoire of healthy behaviors is the basis for cognitive flexibility and self-regulation. An important point to realize is that no electrical current is put into the brain. The brain’s electrical activity are merely registered passively at the scalp and these brain energies are relayed to a computer.
Human EEG consists of random events and rhythms. By means of operant conditioning -- rewarding the presence of certain brain activity patterns and not others -- healthy brain behaviors can be learned and unhealthy brain behaviors unlearned. Therapists typically focus on brain rhythms which have been studied for decades, which are called alpha (8-12 Hertz or cycles per second), beta (15-40 Hz), gamma (40+ Hz), delta (0.1-4 Hz) -- the first four letters of the Greek alphabet -- plus theta (4-8 Hz), the 8th letter, and the more English-sounding SMR (12-15 Hz) which stands for sensorimotor rhythm. Because these rhythms encompass a variety of physiological processes, however, each rhythm is often also dissected into smaller frequency ranges and such "narrow bands" are identified by their numerical range (8-10 Hz, 10-11 Hz).
When someone closes their eyes, alpha activity occurs across most or all of the brain. When he or she opens his eyes in a well-lighted room, alpha rhythms are replaced by beta rhythms, which are fast and low-amplitude waves. The amount of replacement and brain locations where these replacements occur varies depending upon the complexity, novelty, and meaningfulness of the environment, among other factors. Alpha rhythm replacement may involve all of the electrode positions or be selective and only occur at a few sites. Drugs, drowsiness, drive, and time of day generally influence every part of the brain whereas sensory and cognitive demands activate only a selected few brain areas.
Electrodes are positioned on the scalp according to a 50-year standard known as the International 10-20 system which divides the head into proportional distances --10% or 20 % of the way between the dent of the nose (nasion), protrusion in the back of the head (inion), and preauricular points directly in front of each ear. Labels reflect underlying brain areas: FP for frontal pole, F for frontal, P for parietal, C for central, T for temporal, and O for occipital. Sites are numbered with zero or "z" in the middle of the head (midline), followed by larger numbers as electrodes are positioned farther out to either side, with odd numbers alternating with even numbers between the left and right hemispheres (i.e., odd on the left, even on the right). Electrodes are spaced 6 or 7 cm apart on most heads. If more coverage is needed, additional electrodes may be placed halfway between any pair of electrodes. This system owes its endurance to its simplicity and fortuitous division of the scalp into brain regions that remain useful for cognitive and psychiatric research. Finally an EEG signal is always the difference in electrical potential between two electrodes on the scalp. Each electrode may be compared to its neighbor (e.g., C3 to Cz, P3 to Pz), or every electrode can be compared to the same electrode (C3 to Cz, P3 to Cz, O1 to Cz, etc).
EEG training allows an individual to monitor his or her own brain behavior, making visible and discrete what is normally hidden and continuous. This transformation of the invisible to the visible allows anyone to alter the behavior of his or her own brain. Without technological assistance, brain behaviors would be simply too subtle or ambiguous for proper detection and training (i.e., operational conditioning). This is the strength of neurofeedback -- operant conditioning of psychophysiological responses beyond the level of normal (unassisted) observation. EEG biofeedback acts like a telescope to the mental sky. But with this strength comes some ambiguity as brain behaviors (neurophysiological responses) are not so readily classified as good or bad as motor actions can be. That is why children are often trained towards a database norm. The rationale is that if most children on average show a specific brain behavior, a certain incidence of this or that brain rhythm, this behavior ought to be generally healthy and positive. Many neurotherapists guide training by performing a quantitative EEG assessment of an individual before training and even at regular intervals during training.
Behavioral and mental states such as mathematical processing, reading, or relaxation are believed to consist of unique and distinct perceptual and cognitive operations and every mental operation has its own unique EEG profile -- that is, a unique pattern of rhythmic activity in various parts of the brain. This concept is the foundation of functional neuroimaging including functional magnetic resonance imaging (fMRI), a popular method of investigating cerebral blood flow. This concept also provides the rationale for EEG normalization training: One’s brain activity is trained toward a population norm because any deficit or excess of rhythmic activities is likely a result of abnormal neurophysiology and mental irregularity.
Running on a treadmill helps a physician determine how well a patient's heart handles work or stress. Running through a test battery of reading, math, and problem-solving during the acquisition of EEG signals helps determine how well an individual's brain handles work or stress. Eyes closed relaxation or simply opening the eyes may reveal mental shortcomings for some individuals while others require challenges such a general test battery to reveal suspected or known deficits. Continuous attention tasks are often used to reveal processing deficits in attention deficit hyperactivity disorder (ADHD) children and executive control and inhibition tasks for identifying disturbances in the frontal lobe.
A minute of EEG contains a vast amount of information. Frequency analysis reduces EEG to a manageable handful of numbers. Spectral information, as it is called because we examine the entire frequency spectrum for rhythmic patterns, can be presented in tables, histograms, line graphs or the popular brain maps. Brain maps convert numbers into colors, which allows the human eye to quickly detect important patterns. In addition to unusual amounts of energy in various parts of the brain, we can also depict abnormal network activity. Too little or too much reciprocity between brain areas is quantified by means of comodulation and coherence analysis. Comodulation captures the reciprocity of energies between brain areas and coherence captures the timing relationships.
The figure above is an example of a brain-network map of a healthy adult compared to a brain-injured adult of similar age. We are looking down on the head of each person, with their nose on top and ears to either side. Each circle is positioned at one of the 19 electrode sites sitting atop the head and depicts within itself all of the connections between electrodes relative to its position. The color yellow indicates normal function (i.e., database average), green and orange mostly normal, with blue and red indicating too little and too much connectivity, respectively.
As you can see, the healthy adult (left) shows relatively normal amounts of shared energy between electrodes for the rhythm under investigation while the brain-injured individual (right) shows too little communication or reciprocity between areas, notably between the frontal areas of the brain.
The theta rhythm dominates a child’s spectral energy while an adult brain contains most of its spectral energy in a faster rhythm, the alpha rhythm.
When we evaluate children we have to take into account a degree of neurological immaturity. Most of the energy of an infant’s brain resides in the slow-wave delta rhythm and more than a decade of development may pass before an adult brainwave pattern emerges. Theta rhythms are prominent in many children diagnosed with attention deficit hyperactivity disorder (ADHD) because this reflects the immaturity of the ADHD brain. Theta rhythms in an adult or non-ADHD teenager often indicate brain-injury or neurological disease. The brainwave activity of any child may be compared to a database of many normal children in order to identify what parts of the brain, if any, differ in activity and what frequency rhythms are present at these locations.
Many psychiatric and neurological conditions manifest themselves more as disturbances in brain connections than as local damage or disorder. Therapy can focus on restoring activity to isolated brain areas or focus on re-establishing brain networks. Through trial and error any individual gradually develops mental strategies that modify his or her brain rhythms so as to maximize reward and in so doing alter these rhythms for the better. Neurofeedback works at the level of one’s will, as in will power. An individual explores what is and what is not healthy willful behaviors, however indirectly, through the impact one’s will has on one’s brain rhythms. The brain is enormously plastic in terms of function as well as structure and is capable of altering neural pathways in response to reward. Much like our body, our brain also responds to exercise. Neurofeedback provides one of the best forms of exercise -- regulatory practice, the brain practicing at regulating itself.