Differential EEG

Glen M. Sizemore gmsizemore2 at yahoo.com
Sat Mar 13 07:42:57 EST 2004


> GS: The crucial sentence is the last one - the one in parentheses. First,
> have there been any failures to replicate? Second, you haven't described
the
> procedure(s) and there are a number of variables that could be relevant -
> but I understand why you wouldn't go into details....don't get me wrong.
But
> still, as controversial as this sounds to me, one has to be skeptical.
>
> If you really wish to demonstrate the effect, expose each of four subjects
> to all of the conditions, multiple times. If you can get the effect
> repeatedly in individual subjects, then you've got something.
>

NMF: Very good point. I agree whole-heartedly that one should be very
skeptical
and look at the data first and foremost. For me, I believe electromagnetic
fields can interact with biological systems. It makes sense from a physics
and physiological basis. Whether or not these fields can produce the same
effects outside of the controlled laboratory environment (i.e. can
exogeneous source of magnetic fields elicit the complex effects we see in
the laboratory) is something that will still be needed to be debated and
further investigated.

All subjects were exposed to all conditions of the magnetic fields and there
presentation was counterbalanced for each subject. Baseline time
stimulation were recorded and time estimation following field exposures were
also recorded (hence each subject served as their own control). The only
difference was the rotational application of the field. This was to answer
the question whether or not counterclockwise applied fields would effect
subjective time estimations. In addition, there was six configurations of
the magnetic fields used for the exposures. (i.e. three configurations for
one field type and three for another field type). Thus the experimental
design is essentially a two-way analysis of variance with one level repeated
(configuration). The only thing that would have been better for this study
would have been to include the rotation condition as an additional
within-subject factor. (For example, include all field presentations and
rotations, as you suggested, to the subject. There were reasons for not
include it in this study. One potential factor would be a fatigue factor for
the long duration of the experiment. However, a later studies have used both
approaches and found the same thing. The reference is provided below).

GS: Hmmm. Sounds intriguing. I would like to see the individual-subject
data. Any chance you could provide them? For the record, in experiments like
this, it is unnecessary to average the data from individual subjects
together, despite the widespread practice of doing so. If one has plausible
baseline data, then one may demonstrate the effect repeatedly in each
subject (i.e., several replications right there) and repeatedly in the other
subjects (i.e., several replications within each subject as well as the
across-subject replications). Data obtained and analyzed in this fashion can
be used to DIRECTLY DEMONSTRATE the reliability of the finding, and rarely
prove to be spurious.

Err....you may have mentioned, but I'm guessing that you are talking about
humans here? Have you considered using non-humans? Is this done? What has
been found? Off-hand, I can think of about 4000 experiments (assuming one
can show some kind of effect).

BTW, was the procedure supposedly free of experimenter-induced artifact?
What was the nature of the "time estimation" task?

NMF: You are completely correct, there are numerous variables that could
interact
and influence the effects. With respect to the findings, explained variance
was over 50% in most cases, which equates to a correlation coefficient of
approximately 0.7 (In terms of statistical power and robustness, that would
be a relatively moderate to strong effect and was actually an impressive
effect size in my opinion. I would have thought the effect size is
smaller). In my opinion there is no doubt an effect. I provided the
reference citation, so I wasn't trying to be cryptic regarding the
methodology, thus anyone interested could read it. (I realized now that I
forgot to put the journal citation, which I can imagine probably makes it
questionable. Anyhow. The paper was published in Neuroscience Letters
(1999) for all those interested in the exact methodology.) I included the
point at the bottom that the study had been replicated b/c obviously some
people would raise that point. The good thing is that it was replicated and
found the same exact trend. Actually they even extended the findings to
control for other potential and influencing variables. That replication
study, I believe, was published in 2002 in Perceptual and Motor Skills by
Richards and colleagues.

GS: I know you weren't trying to be tricky. Anyway....I'd like to see the
individual data; I can't emphasize this enough despite the minority status
of the position. It is easily possible to "get an effect" in less than ½ the
subjects and still obtain statistical significance. Where individual-subject
data CAN be examined (as when each subject is exposed to the levels of the
independent variable, and where the baseline is replicable - one may return
to the baseline conditions after each exposure, for example) they SHOULD be
examined. Again, if you can turn the effect on and off at will in, say, 4 of
4 individuals, then there is no need to "infer" the effect with inferential
statistics, the reliability is directly demonstrated and the generality may
be established in similar ways via systematic replication in other
laboratories).

Now, if one does keep obtaining a statistically significant effect that is
not demonstrable in most of the individuals, then one must track down the
source of this difference - of course, one only knows of this if one
examines the individual-subject data.
NMF: (NOTE: The problem for the skepticism, in my opinion, stems from the
rather
grossly poor and incorrect methodological approaches undertaken in the
childhood leukemia studies and the cancer incidence studies regarding
exposure to ELF electromagnetic fields. The general public is given a
completely mixed signal regarding the effects of ELF EMFs. The problem is
obvious to anyone reading the literature. One study reports one thing,
another reports something different. With all of this aside, when one
actually seriously looks into this area of research one immediately sees an
interesting trend regarding those authors who report one thing and those
reporting another. When you look at the government funding agencies
supplying resources for these studies the reason for the direction of the
trend often becomes apparent. (By the way, this goes for both sides
investigating the research question). With the continual emergence of TMS
for clinical and experimental research, the eventual probing into the
mechanisms underlying these processes will be eventually (hopefully)
elucidated.

GS: I am definitely intrigued, but unconvinced there is an effect there. I
am, however, completely open to the possibility that there is, and I think
that it should be relatively easy to establish using a few non-humans in
extended studies.

Cordially,

Glen

"NMF" <nm_fournier at ns.sympatico.ca> wrote in message news:Xwa4c.28595





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