linked ears

[Guest guest]

The reason the linked ears are important is that they remove any effect of differential activation patterns in the temporal lobes. Since the earlobe or mastoid references, which are largely but not completely inert, do pick up fields from the temporals, if the temporal lobes are quite different, that difference will appear throughout the EEG.

For example, if F3 and F4 have amplitudes in, let's say, alpha of 9u on both sides, but the temporal lobes have alpha levels of 1 at A1 and 2 at A2, when we subtract the reference signal from the active, we'll end up with a reading of 8u (9-1) at F3/A1 and 7u (9-2) at F4/A2. In other words, what is really a difference in the temporals will APPEAR to be a difference in the frontals, which really is not there.

If we link the ear references, then an averaged value of 1.5 will be used against both F3 and F4, and the F3 and F4 values will both be 7.5u and appear equal, as they in fact are.

So, if the temporals are pretty much alike, linking the ears has a minimal effect. If they are quite different (not uncommon, since they are the furthest apart of the sites we measure, they have very different functions and they are very susceptible to blows to the head), then the whole assessment can be skewed by not linking the ears.

Also, any coherence measurements will be less valuable, since they are measured against different signals instead of the same signal.

Does that make the assessment " invalid " or useless? Probably not in most cases, though it can result in a less-than-accurate picture and perhaps less successful training plans.

Pete

Pete,

Pursuant to our discussion last evening, is there any value to an assessment done without linking the ears? Does omitting the jumper invalidate any part of the assessment? Or should one be wary about forming conclusions about any one part of the reports page, e.g. locking?

Jill

-- Van Deusen

pvdtlc@...http://www.brain-trainer.com305/433-3160The Learning Curve, Inc.

[Guest guest]

Marc~

Here is a post Pete wrote back in April that might answer some of your questions.

~

Re: linked ears

The reason the linked ears are important is that they remove any effect of differential activation patterns in the temporal lobes. Since the earlobe or mastoid references, which are largely but not completely inert, do pick up fields from the temporals, if the temporal lobes are quite different, that difference will appear throughout the EEG.

For example, if F3 and F4 have amplitudes in, let's say, alpha of 9u on both sides, but the temporal lobes have alpha levels of 1 at A1 and 2 at A2, when we subtract the reference signal from the active, we'll end up with a reading of 8u (9-1) at F3/A1 and 7u (9-2) at F4/A2. In other words, what is really a difference in the temporals will APPEAR to be a difference in the frontals, which really is not there.

If we link the ear references, then an averaged value of 1.5 will be used against both F3 and F4, and the F3 and F4 values will both be 7.5u and appear equal, as they in fact are.

So, if the temporals are pretty much alike, linking the ears has a minimal effect. If they are quite different (not uncommon, since they are the furthest apart of the sites we measure, they have very different functions and they are very susceptible to blows to the head), then the whole assessment can be skewed by not linking the ears.

Also, any coherence measurements will be less valuable, since they are measured against different signals instead of the same signal.

Does that make the assessment "invalid" or useless? Probably not in most cases, though it can result in a less-than-accurate picture and perhaps less successful training plans.

Pete

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