From: Grant Bright, Ph.D. (gbright_at_b...)
Date: 2001-06-13 21:16:56
Jim makes a good point I would agree with completely...Frans, for testing a14hz @ 5 to 50 uv sine wave or saw tooth from a signal generator will givegood results. There are times in eeg we see values of over 200uv...so the amplifiers should not be swamped by this level and should remain linear.
Jim also raises another very good point to examine in software issues lateron, digital filters in real time depicting the waveform the various "bands" delta, theta, alpha, beta would be very good to have.
In doing clinical analysis, from which I am taking a break right now, I always look at the characteristics of the raw waves, are they "pointy or sharp?" or are they well formed sinus? or do they look like molars? are there "spindles?" These qualities are important to examine in addition to the actual numbers.
Within "numbers" it is important also to distinguish RMS, average, and Peakto Peak voltage values. I also look at power. For you RF engineers, this is not the power (VxI) in radio. In eeg is V squared. This was created to cause elevations to stand out. 1 squared is still one, but 10 squared is 100...so it shows more.
At first I thought in eeg, this power measure is silly, But after examininga several hundred Qeeg records, I see its usefulness and use it.
Best regards to all
Grant
----- Original Message -----
From: peterson_at_d...
To: buildcheapeeg_at_yahoogroups.com
Sent: Wednesday, June 13, 2001 11:31 AM
Subject: [buildcheapeeg] Re: BrainWaveSimulator.
--- In buildcheapeeg_at_yahoogroups.com, "frans smith" <f.smith_at_c...> wrote:
> Hi,
> Simpel question.
> Is the shape of a brainwave important ???
> Can i just use a sinus 14hz, to act as a brainwave at 14hz ?.
> That is, to use the signal to build software ?
> (not raw brainwaves) but just software wich respond when
> a special brainwave frequency is present, not diagnostic.
> thanks
> frans
For our purposes, I think you can use a sine wave to represent the
brain signal. However, as a sort of side-note, some theorists do
think that the shapes of the waveforms are important because they can
indicate the presence of harmonics, which would be indicative of
otherwise concealed higher-frequency patterns. Thus a "saw-toothed"
theta wave might have a different clinical meaning than a square-wave
delta, etc., or at least these theorists say so. I've heard Joel
Lubar and Marvin Sams discussing this issue and disagreeing with each
other. However, I know of no commonly available neurofeedback
equipment that is capable of distinguishing one waveform from another
"on the fly." This is accomplished, at least in the biofeedback
world, by "eyeballing" the raw wave forms. No feedback systems
exist, to my knowledge, which would provide differential feedback
based on wave form characteristics. Once again this motley pack of
brilliant amateurs has found its way onto the front lines of the
field. Hope this is helpful.
Yahoo! Groups Sponsor
To unsubscribe from this group, send an email to:
buildcheapeeg-unsubscribe_at_egroups.com
Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:31 BST