Neuroconcepts

Applied Neuroscience website of
Behavioural Neurotherapy Clinic

Quantitative EEG (QEEG)

Quantitative EEG topography, sometimes referred to as "Topometric Brain Mapping" measures the electrical patterns present on the surface of the scalp. Accessed and analysed through digital technology, these measurements primarily reflect cortical electrical activity or "brainwaves." QEEG databases are used to enable the QEEG of patients to be statistically compared to those of a "normative" data base.

When QEEG deviances from normal correlate with areas known to usually perform specific functions it is suggestive of dysfunction in that particularly area and may become the target for Neurotherapy

Brainwave frequencies
Some brainwaves occur at faster frequencies, or wave speeds; some are quite slow. The classic names of these EEG bands are delta, theta, alpha, SMR and beta and are identified according to their frequency, which is measured in terms of repetitions (or "cycles") per second ("cps") or "Hertz" (Hz). There are some variations in opinion as to the best way to group brain waves into clinical bands, but generally, it is agreed that, from slow to fast, brain waves should be grouped as follows:
  • Delta brain waves (1-3 Hz) are the slowest, highest amplitude brainwaves, and are present primarily during sleep or when in an empathetic state. Excess delta activity in the awake state is usually indicative of dysfunction.
  • Theta waves (4-8 Hz) are present when daydreaming or fantasising. At the same time, creativity and intuition are also associated with theta waves. This contrast occurs because theta waves occur at two levels: The lower range of theta (4-5 Hz) basically represents the twilight zone between waking and sleep. It is a profoundly calm, serene, floaty, drifty state. In this range, conscious intellectual activity is not occurring. It is also the range of frequencies produced in excess by children and adults with ADHD.

By contrast the higher range of theta (6-8 Hz), when present at midline frontal sites is associated with a state of highly inwardly focused attention. This is where the mind goes when we are engaging in complex, inwardly focused problem solving, such as mental arithmetic. This is also the level people enter when they go into in a deep hypnotic or meditative state. Persons experienced in self-hypnosis and highly hypnotizable persons (as well as very proficient meditators) produce more 6-8Hz theta brainwaves in both a waking state and in hypnosis.

  • Alpha waves (8-11 Hz) are slower and larger. They are associated with a state of relaxation and basically represent the brain shifting into idling gear, relaxed and disengaged, waiting to respond when needed. If one merely closes his or her eyes and begins picturing something peaceful, in less than half a minute there will be an increase in alpha brainwaves. Alpha is present typically when one feels at ease and calm or in a position to change one's mind efficiently and effectively in order to accomplish a task.
  • Sensory Motor Rhythm (12-15 Hz) measured over the sensorimotor cortex are brain waves associated with mental alertness and readiness for action, combined with behavioural stillness.
  • Beta waves (16 Hz and above) are small, faster brainwaves associated with a state of mental or intellectual activity and outwardly focused concentration. Beta waves are present when one is thinking, problem solving, processing information, or anxious.

Having made these differentiations among the various brain wave bands, it must also be pointed out that at any one time everyone has a mix of all those brainwave frequencies present in different parts of the brain. However research has shown that:

  • In the awake state, delta brainwaves also occur when areas of the brain go "off line" to take up nourishment.
  • If one is becoming drowsy, there are more delta and slow theta brainwaves present. If someone is inattentive to external events and daydreaming (internalising), there is more low frequency 4-5 Hz theta present.
  • If individuals are exceptionally anxious and tense, excess high frequency beta activity is present.
  • Persons with  ADHD, learning disabilities, and head injuries tend to have excess slow waves (usually delta, slow theta, and sometimes excess alpha). When excess slow wave activity is present in the executive (frontal) part of the brain, it is difficult to control attention, behaviour, and emotions. Such persons may have serious problems with concentration, memory, controlling impulses and moods, or with hyperactivity. They cannot focus well and exhibit diminished intellectual efficiency.

While all types of brain waves are always present regardless of the state of mind, the dominant frequency generally describes an individual’s state of consciousness. No frequency is "better" or "worse" than any other. In fact, each is essential to healthy mental functioning. Problems arise when humans have the improper mix of frequencies for dealing with the task at hand.

Brain Wave analysis or Topometric brainmapping

QEEG.JPG

In the Above QEEG maps, The rows represent QEEG measures, while the columns represent frequency bands. Black is exactly on the database mean while one colour on either side is considered the normal range. The hotter the colours, the more the measure is in excess, while the cooler colours indicate deficits.

QEEG is an assessment tool used to aid in identifying mental health conditions by means of statistical evaluations of the EEG. The QEEG is useful to the clinician as an adjunct to traditional clinical assessment, as it provides a sensitive and specific method to detect subtle variations in the activity of the brain. Subtle brain wave variations might otherwise go unnoticed by the clinician, even with a traditional, visually inspected EEG. But the computer-based QEEG may provide evidence of an underlying dysfunction that needs to be recognised, evaluated and treated.

QEEG is the only widely available technology that can be used for this purpose today.

In the past QEEG reports have not been readily understandable to the average clinician, who does not have extensive training in QEEG physiological correlates or clinical neuroscience. Up until now, these factors have been barriers to the broader acceptance of QEEG as a clinical science. Nowadays however, the use of a scientifically validated QEEG database (John &  Prichep, 1988) whose establishment and validation has been extensively peer reviewed in the literature, provides well normed data sets, standardisation of processes and clarification of information reported. This makes the resulting reports and interpretations more readily understood and more useable by healthcare practitioners.

High Specificity of QEEG

Research has found that QEEG has a high level of reliability that is equal or superior to routinely used clinical tests such as mammograms, cervical screenings, blood tests, MRI and CAT scans. A comprehensive literature review (Hughes & John, 1999) in the Journal of Neuropsychiatry and Clinical Neurosciences reported,

"Of all the imaging modalities, the greatest body of replicated evidence regarding pathophysiological concomitants of psychiatric and developmental disorders has been provided by EEG and QEEG studies."

QEEG measures the minute electrical activity of a person's brain and then, using proprietary software, compares that unique pattern to known databases of "normal" and "abnormal" patterns. This type of computer-driven statistical analysis is particularly useful in evaluating difficult and borderline cases.


Neuroconcepts: 2/314 Manningham Rd. Doncaster VIC 3108

Email: neuroconcepts@adhd.com.au  Tel: 03 9848 9100  Fax: 03 9848 9300

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