Use of EEG technology is shared by at least two disciplines

As EEG is used for different goals by different groups, the same is true for other tools such as hammers We do not require a gavel to be manufactured using specifications of a carpenter’s hammer

Standard 19 electrode positions

Survey of 2009 EEG papers on Medline for humans waking state, 25% clinical, 75% quantitative Over 40,000 QEEG papers since 1965 First QEEG paper = 1932 Dietsch (1932) analyzed EEG using discrete Fourier transforms (1831). Fast Fourier Transform (FFT) algorithm invented (Cooley & Tukey, 1965), allowing practical spectral applications – Dumermuth & Fluhler (1967) applied FFT to EEG

Frequency analysis Jean Baptiste Joseph Fourier ( )

Energy (Amplitude) & Speed (Frequency)

SKIL Database – Individual dominant frequency

Some of the signal properties that can be quantified

Evaluation of cortical activity. Each brain map consists of 19 electrode sites evenly spaced across the head. Color indicates microvolts (data or raw view) or statistical deviation from a comparison group average (stat view). Spectral magnitude coefficients that exceed +/- 2 standard deviations are indicative of localized hyper- or hypo-excitability in cortical neuronal pools, depending upon the frequency of interest

SKIL Database Peer review publications of SKIL database Johnston et al, 2005 (Clinical EEG) Lorensen & Dickson, 2003 (J Neurotherapy) Mean 28.2 years+/- 6.4 years 75% male n=135 using replicated files from each participant

Why amplify? 10 2 volts - Wall socket volts - EKG (millivolts) volts – EOG volts – EEG (microvolts)

Sources of Artifact Equipment Computational Neural, non-cerebral (muscle) Neural, cerebral, mixed states – alertness changes, sleep, unstable background – transients Inferential – Improper mental processes – Improper frequency correspondence

Brain Maturation Healthy Adult Healthy Child 4-8 Hz 8-12 Hz

The more neurons recruited into a rhythm, the higher the spectral magnitude (or power)

Time delay between brain areas recruited into the same rhythm is indicated by phase

Activity and Connectivity

How to show 361 (19x19) site-pairs Raw Data VIEWS Statistical

Data and Statistical (z) views

Network Maps (anterior callosotomy case)

Behavioral differences from norma Activity Connectivity

Frequency information localized and shared Coherence – (Wiener, 1930; Goodman, 1957; Walter, 1968) Comodulation – (Pearson, 1896; Kaiser, 1994)

…coherent when phase difference is stable …comodulated when magnitude difference is stable Signals are …