About Us Downloads Contact
Low voltage EEG
Beta Spindles
EEG vs. Perfusion
Neurological EEG

Diffuse Slow Activity

This Phenotype is characterized by the following:

  • Increased slow activity (Theta and Delta)
  • Sometimes slowed alpha peak frequency
  • Examples: Alzheimer’s dementia, TBI

Treatment advice:
Neurofeedback: Reward higher frequencies (12-18 Hz) at Cz or sensorimotor strip, depending on other localized effects (frontal alpha) include other locations. If lower alpha peak frequency is present, gradually uptrain alpha peak frequency to normal levels (inhibit lower alpha and reward higher alpha.
Medication: Stimulants

The above is only a brief summary, for more detailed information please read the original paper by Johnstone, Gunkelman & Lunt (2005).

Example 1: Male 18yrs, sleeping problems.

The raw EEG during Eyes Closed showed a posterior slow rhythm in the raw EEG of 7-8 Hz. In the FFT's this is also indicated as an alpha peak around 7-8 Hz. Given the distribution of this slow rhythm (posterior), it's occurence during Eyes Closed and it's relation to impaired memory it can be characterized as a Slowed Alpha Peak Frequency. NOTE: this activity is NOT Theta.

EEG tracings with slow posterior EEG rhythm

QEEG frequency content (FFT)

QEEG spectral content compared to normative database

Raw EEG: Note the slow alpha

QEEG: Spectral content

QEEG: Spectral content

Below also see the specifically impaired memory recall which is often seen with decreased alpha peak frequency (also see studies from Klimesch) and the decreased Alpha-2 or high-alpha (10-11 Hz). Also note the slightly elevated 16-17 Hz being a harmonic of the alpha and no real effect.

Neuropsychology: Memory recall scores QEEG: Single Hertz bins, note the shifted content of the alpha band, with decreased low alpha and slightly increased slow alpha

Cognition: Memory recall scores

QEEG: Single Hertz bins, note the shifted content of the alpha band, with decreased low alpha and slightly increased slow alpha

The concurrent evidence shows a slowed EEG marked by a severely slowed alpha peak frequency which is further supported by the impaired memory performance. Therapy should focus on increasing the alpha peak frequency by rewarding high alpha and inhibiting low alpha (6-8 Hz) at Pz during Eyes Closed. If the therapy has an effect an improved memory recall should be noted.

Example 2: Male 69 yrs.

This example is a similar case with a posterior slow rhythm of around 6-7 Hz and severely impaired memory recall. Interestingly, note that the alpha peak frequency of this client is slower as Example 1 and this client also has a more severely impaired memory recall, demonstrating the close relation between Alpha Peak Frequency and memory recall!

Raw EEG example QEEG Spectral content
Neuropsychology: memory recall scores

Raw EEG, QEEG Spectral content and memory recall: Note the clear relation between very slow alpha peak frequency (8 Hz) and impaired memory recall.

In the pictures below however, look carefully. The increased Theta is NO THETA! We saw above that this posterior slow activity was a slowed alpha peak frequency, which was also related to impaired memory recall. This slowed alpha activity will show up as Theta but in fact is still alpha.

In this respect always think about the following example: Say that a guitar most of the times plays between 8-12 Hz, and now suddenly during a solo my guitar produced a 14 Hz note...did my guitar at that moment transform into a violin or is it still a guitar...? Hence alpha is alpha by it's characteristics (posterior, sinusoidal rhythmic activity attenuated by eyes opening) NOT alone by it's frequency!

QEEG spectral power for delta, theta, alpha and beta

QEEG spectral power (FFT): single hertz bins from 1-40 Hz.

QEEG Single Hertz bins: Note the increased 6-7 Hz and increased 'Theta'
band; but in reality this is due to a very slow alpha peak frequency.


Example 3: TBI patient pre- and post-neurofeedback

Below see the pre- and post-QEEG for a client with Traumatic Brain Injury after a car accident. This client showed a specific right frontal slowed alpha peak frequency and impaired neuropsychological function on the pre-assessments (about 3 years after the accident). The right-frontal slowing is related to the TBI. This client underwent a lot of Neurofeedback sessions and made a lot of progress clinically. Note the normalization of most QEEG parameters as indicated by most P-values being close to 1 after treatment.

This example demonstrates that the clinical improvements clearly correlate to the normalized QEEG and that this Phenotype can be treated effectively.


pre-treatment QEEG TBI

pre-treatment QEEG FFT and topographical distribution


QEEG post-treatment TBI

QEEG post treatment TBI spectral content

For more information on the QEEG methods used by Brainquiry also see the professional section on QEEG.