Delta

Delta is the slowest electrical frequency that may sometimes be trained using neurofeedback. The rhythm generator for the delta rhythm is the brain stem and hind-brain—so it does not part of the autonomic nervous system.  Delta is unconscious.

Generally, delta in the 0-2 Hz range indicates that part of the brain is in a state of deep sleep. At times this is not good.  Delta in the range of 2-5 Hz indicates drowsiness and may be the result of the training being done. Sometimes a change of diet does more to alleviate this problem than biofeedback. The culprit is usually sugar, processed flour and cereals or the drinking water.

Delta isn’t a really common thing to find.  Spikes of it can be related to head injuries or artifacts.   (Delta is also the frequency of the coma), and it can be resistant to training.  Sometimes when it falls, other things appear, which is why I like to leave the squash in place.

Generalized slow activity is often effectively trained on the midline.

Defining Delta

We may define delta differently from a neurologist, and there are many definitions of it.  Neurologists often look at the morphology of wave patterns, especially looking for epileptiform activity.  We look at numerical values representing amplitudes in each frequency.  If we define delta as 1-3 Hz, as we do in the TQ Assessment, then a fair portion of that is 1-2 Hz., and there is no argument that activity this low in a waking EEG is largely artifact.  However, saying that finding delta anywhere in any amount in someone in a resting state is abnormal would be a stretch in my experience–and I’m guessing also in that of those who use QEEG’s.

Delta can be present without being abnormal.  It’s a matter of how much of it and where it is and what happens to it when we activate.  It’s perfectly possible that we are more likely to be asked to do assessments of folks who are “abnormal” in a neurologist’s terms.  Certainly a preponderance of slow activity is a very common finding in our clients, and that’s not “normal.”  I’ve looked at my assessment a number of times.  Look at your own.  See any delta there?  I see it in mine.  But you and I and many of our clients are functioning fairly effectively.  So maybe “normal” isn’t a very useful concept in this case.  When we see delta levels higher than we expect, then we have a training option, especially if there are performance issues that appear to be related.

Delta Amplitude

If you find a spike of delta in one site or some contiguous sites, it can be an indicator of a lesion–normally white-matter damage, with neurons still functional but not connected, so they aren’t sending or receiving signals and drop to the lowest common-denominator rhythm, delta.  This is not likely the issue if you are seeing delta all over the brain.

As a general rule, evenly distributed, high amplitude delta is indicative of slow brain maturation, and training to decrease Delta amplitude usually proves beneficial. Almost any location will work but FZ, CZ and PZ seem to work better most of the time.

Temporal high amplitude Delta in the 0-2 Hz range usually accompanies a brain that is not very alert. Temporal high frequency high amplitude Delta in the 2-4 Hz range is an indication of an intuitive mind. This can be confirmed with high amplitude 100 Hz on either the right or both temporal lobes. (Training 100 Hz to increase intuition did not work.)

Frontal high amplitude Delta usually accompanies low levels of concentration, focus, attention and awareness. The lower the frequency of the Delta the more difficult to resolve these issues. Obsessive behaviors tend to manifest more with lower frequency frontal Delta. Training to decrease frontal Delta usually proves beneficial. I had good luck by training to decrease frontal Delta (0-3 Hz) while increasing parietal Alpha (10-14 Hz) either concurrently or following the Delta work.  I would definitely try a squash or windowed squash, starting, say, at Afz/A1 and Fpz/A1.

I never did much work with high amplitude central or parietal Delta but I did observe that training to increase parietal Alpha tended to decrease parietal Delta and that excessive central Delta tended to decrease while the client was working to decrease frontal Delta.

According to the research done at the research center I ran while working for Lexicor, it all depends upon where the high amplitude delta is located in the brain, the frequency of the delta and the delta coherence between any two locations. In my opinion and experience, anytime inhibiting delta is not working well, the problem is hyper coherent Delta. Find the locations involved and break up the hyper coherence and the delta “problem” is quickly resolved.

Generalized delta can be an indication of dissociation as well.  People who have had traumatic experience will often have high levels of delta in which are buried the experiences that could not be processed.

And generalized delta can also be related to poor blood supply and hypo-oxygenation, which results in neurons being unable to sustain higher frequency pulse rates.  Very often we see children who had early births or long or difficult birth processes (cord wrapped around the neck, long time in the birth canal, etc.) whose brains simply don’t provide much oxygen.

When delta increases at task at the F and even C sites, you might want to rule out that it is simply eye movement or eye blink activity.

Synchronous Delta

There is some evidence that, as delta is the unconscious mind, Synchronous delta (not just delta) can be related to a kind of connection to the collective unconscious.

With delta and theta and even some of alpha there is a difference between synchronous and de-synchronized activity.  Synchronous delta might be related to tuning in to the whole., but delta in most brains during waking states is not synchronous.  It just represents very low metabolic activity, and perhaps low oxygenation.

Delta Coherence

As a rule, hyper-coherent delta is indicative of a closed head trauma while hypo-coherent delta usually accompanies learning disorders. Break up the coherence by training in the opposite direction for five minute intervals using an A – B – A format of 1, 3, 5 or 7 five minute mini sessions or until the client tires of the process. Change the direction of the training.  Repeat this process but always end by training in the same direction as your first mini session training.