Brain waves occur at various frequencies, that is, some are quick, some quite slow. The classic names for these "EEG bands" are delta, theta, alpha and beta. The dominant wave pattern you see above is alpha; these waves happen between 8 and 13 times per second, or 8-13 Hertz (Hz). Alpha represents a sort of "idle" state, or "ready but not doing much" state and is normally fairly large over the back third of the brain when the eyes are closed and when you are awake. Alpha disappears when we either get mentally busy (e.g., open the eyes, start doing intense mental work even eyes closed) or when we become drowsy. Thus the presence of alpha can show the presence of an awake, resting state. If it is present at a fairly high voltage when the eyes are open, this would usually indicate an inattentive, daydreamy state. In fact we often see this sign in adolescents and adults with attentional difficulties.
When we get mentally busy and engaged, we should see alpha "block," or reduce significantly in size. In its place we see mostly smaller, quicker "beta" waves. The beta family of waves happen at frequencies from 16-35 Hz, with higher frequencies known as "gamma".
Delta and theta waves are relatively slow. Delta is usually defined as waves occurring from 1-4 times per second (1-4 Hz). Theta occurs at 4-7 Hz. During drowsiness, first alpha disappears, then the size of theta waves begins to increase. As sleep begins, theta waves get quite large, then become mixed with and eventually give way to slower delta waves.
The presence of delta and theta waves in the waking, eyes open EEG is normal, but only if the waves are fairly small. High amplitude slow waves can be signs of various neurological and psychological problems, ranging from epilepsy to ADHD.
For years all that was possible was recording these waves on paper with the traditional polygraph. Over the last 25 years, advances in signal processing made it possible to sample these waves many times per second (usually 128 or 256 samples per second; our current equipment samples at 4096 per second) and to analyze them in various ways. Using this technology we can now measure precisely the amplitude and frequency of waves of interest, be fairly exact about the scalp distribution of the waves, and even compare a client's qEEG to a normative life-span wide reference database that shows how the person's brain activity compares, on the average across a particular task, to healthy people of similar age and same sex.
We use a 32
EEG system, the Truscan 32 by Deymed Diagnostic,
which allows high quality digital recording as well as EEG biofeedback.
quantitative EEG (qEEG) shows the actual brain electrical events
associated with periods of inattention very clearly, for example the
"sleepy" signals. The recording below shows big "theta" waves over the
front of the brain, indicating periodic "sleepiness" in these critical
The excess theta pattern is the most common pattern seen in
children with ADHD diagnoses. About 80% show this pattern. A
recent study (Synder & Hall, 2006) meta-analyzed 9 QEEG studies
covering a total of 1498 children diagnosed with ADHD. The study showed
an amazing sensitivity and specificity of 94% for identifying ADHD from
the QEEG alone. That means that if excess theta and diminished beta
activity is present, there is very likely going to be an ADHD
diagnosis. The pattern correctly predicts ADHD 94% of the time.
Department of Psychology, University of North Texas Health Science Center at Fort Worth, Fort Worth, Texas, USA.
A meta-analysis was performed on quantitative EEG (QEEG) studies that evaluated attention-deficit hyperactivity disorder (ADHD) using the criteria of the DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, 4th edition). The nine eligible studies (N = 1498) observed QEEG traits of a theta power increase and a beta power decrease, summarized in the theta/beta ratio with a pooled effect size of 3.08 (95% confidence interval, 2.90, 3.26) for ADHD versus controls (normal children, adolescents, and adults). By statistical extrapolation, an effect size of 3.08 predicts a sensitivity and specificity of 94%, which is similar to previous results 86% to 90% sensitivity and 94% to 98% specificity. It is important to note that the controlled group studies were often with retrospectively set limits, and that in practice the sensitivity and specificity results would likely be more modest. The literature search also uncovered 32 pre-DSM-IV studies of ADHD and EEG power, and 29 of the 32 studies demonstrated results consistent with the meta-analysis. The meta-analytic results are also supported by the observation that the theta/beta ratio trait follows age-related changes in ADHD symptom presentation (Pearson correlation coefficient, 0.996, P = 0.004). In conclusion, this meta-analysis supports that a theta/beta ratio increase is a commonly observed trait in ADHD relative to normal controls. Because it is known that the theta/beta ratio trait may arise with other conditions, a prospective study covering differential diagnosis would be required to determine generalizability to clinical applications. Standardization of the QEEG technique is also needed, specifically with control of mental state, drowsiness, and medication.
pattern is very responsive to the stimulant drug methylphenidate, since
it "wakes up" the frontal and prefrontal cortex enough so that it can
do the critical jobs of motivation, impulse control. Until the
medication wears off.
Many adolescents, some pre-adolescents and many adults with ADHD
diagnoses show too much alpha, with normal levels of theta. This is a
different type of brain. The excess alpha pattern does not commonly
respond to methylphenidate or amphetamine very well. The excess alpha
pattern represents vast processing regions that are "awake" but are
failing to "allocate" their resources to the job at hand. This causes
the experience of "I heard your voice but I have no idea what you just
said." The pattern looks like this:
This recording shows high amplitude alpha waves over most of the
back half of the head. Notice the first example, the excess theta waves
were over the front of the head (top four tracings plus the third one
from the bottom).
Some people, often with more severe difficulties, show a mixture
of alpha, theta and often delta waves. This next example is from an 11
year old girl previously diagnosed with Pervasive Devlopmental Disorder
NOS, a major failure to develop age-appropriate social and academic
Some of the big waves are alpha, the wider ones are theta and the widest ones are delta. Contrast these patterns with the following example of entirely normal activation during a task:
Notice all the waves are much smaller. There are some little
alpha waves, e.g. immediately above the word "normal", but they don't
go on for a long time and they are not big. This indicates "pretty
good" allocation of brain resources to the job.
You can see clear signs of over-excitement in some
people, correlating with high anxiety. The next recording shows
an anxious adult female with her eyes closed. Notice there is very
little alpha activity, but a whole lot of beta (the small, close
together waves). This person was also diagnosed with "ADHD", but
reacted very badly to a stimulant medication given by a physician who
was simply "going by the book" and diagnosing ADHD by the symptoms, or
complaints. Examining the QEEG would easily have suggested this person
is already very aroused, over-excited and that anxiety and distracting
thoughts were causing the inattention. Contrast this eyes closed
"resting" recording with the normal recording at the top of this
QEEG is not intended to be a "stand alone" diagnostic or as a substitute for other medical diagnostics. It is, however, a helpful adjunct which can guide prognosis and intervention. qEEG is best used as an tool to aid in the clinical diagnosis of various dysfunctional states and not as a substitute for clinical judgment and medical opinion. The qEEG should be combined with other medical, psychological and neuropsychological data to best aid the patient.
The sister technology to qEEG is called EEG biofeedback, neurofeedback or neurotherapy. The qEEG provides the "targeting" information. That is, it tells us where and under what conditions (reading, listening, math, etc.) the problem is worst. This analysis allows accurate electrode placement for feedback and suggests the tasks that should be used during therapy. Neurotherapy is EEG feedback-assisted cognitive behavior modification. It couples EEG feedback with the full range of traditional cognitive behavior therapy methods, including imaginal rehearsal, correction of maladaptive thought patterns, and rehearsal of new skills. We commonly utilize intensely activating, challenging tasks during the sessions to enhance brain activation and teach what it feels like to be focused and functional again. The EEG feedback signals the patient when their brain is in fact in a more activated state, indexed by decreased delta and theta brain wave amplitudes, and increased beta and/or alpha amplitudes.
Neurotherapy is no panacea. Like any therapy it works best with people who are motivated, who want to improve, who are experiencing some significant suffering from their symptoms and who are not so discouraged by years of trouble that they don't even want to try any more. In this latter case, depression, helplessness and negative attitudes toward the self - and often others - may have to be treated before the underlying attention, organization or learning problems can really be addressed.
Behavioral Medicine Associates, Inc. has many very satisfied patients who can testify that neurotherapy has reduced their symptoms of ADHD, anxiety, depression and brain injury. Memory has been improved, emotional instability has been decreased or eliminated, and executive function has been improved.
The instrumentation is expensive and requires serious study and training to use competently. Proper instrumentation has only recently become generally available. Two national organizations to promote and develop this approach have been formed in the last three years. Attendance at the ISNR national conference has grown to 450 this year. More clinicians are using neurotherapy each year. For psychologists and others who did not have extensive graduate training in neurobiology in graduate school, it takes some serious study and work, including supervision, to become competent in neurotherapy. So the spread is slow, but steady.
Certification in neurotherapy is advancing and, we believe, necessary so that insurers can choose to reimburse only certified clinicians. A national biofeedback organization, the Biofeedback Certification Institute of America, certifies health care practioners as competent to perform a wide range of types of biofeedback. The BCIA was established in 1981 to certify practitioners in peripheral (EMG, temperature, GSR) biofeedback techniques and now has certification in EEG biofeedback (neurofeedback) available via tests administered at the major annual conferences of the ISNR and AAPB.
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