Inhibit Options

by Sue Othmer | April 12th, 2006

I have been using wide inhibits recently with just about everyone. Wide inhibits are typically 2-13 and 14-30 Hz, and easily cover the entire 0-30 Hz frequency band of interest. I moved to wide inhibits a few years ago, first for a stronger effect on fibromyalgia symptoms. I then gradually tried the wide inhibits with more and more clients with different symptom profiles and was pleased with the stronger training effects they produced.

We can think of the wide inhibits as catching inappropriately high amplitude activity at any frequency. In awake-state training an appropriately activated EEG will be desynchronized and low amplitude across the entire band. So the wide inhibits are effective at detecting and inhibiting abnormal bursts of activity at any frequency. Separating the entire band into high and low components allows us to set thresholds separately on the two segments that might have rather different amplitudes.

The wide inhibits are clearly stronger in their clinical effect than more narrowly targeted inhibits. As such they require a more careful adjustment of the reward frequencies. There has been some thought that moving to wide inhibits requires a lowering of the reward frequency, but at this point I think that it is more about a stronger effect and stronger need to optimize the reward.

I am usually looking for ways to make the training stronger and more specific, but there certainly are times when we would like a less powerful effect. One way to achieve a milder training effect is to back off on the inhibits. This could mean using narrower inhibit bands tailored to the EEG. Or it could mean decreasing the percent time over threshold in the inhibit bands — say from 10 or 15% (low inhibit) and 5% (high inhibit) down to 5% and 2%.

I have been setting up new training screens with BrainMaster and BioExplorer that will allow us to explore other inhibit options. With multiple inhibits we might break the entire frequency range into six or seven segments instead of just high and low. This should allow a more accurate fit of the thresholds to the EEG during training. And my expectation is that it will give us again a stronger effect than the wide inhibits. If you want to try training with multiple inhibits with the BrainMaster, download the EEG settings files and EEG Demo folders included in this EEG Newsletter. Use the EEG 1- Channel Multiple Inhibits settings.

We are also preparing to use two-channel training as a means of strengthening our inhibit strategy. If we train T3-T4 with a one-channel bipolar placement, then we are both rewarding and inhibiting on the difference signal. We have found, at least in the general case, that rewarding the difference is more effective than rewarding the sum. We have argued that rewarding the difference promotes desynchronization within the reward band and thereby increased stability of brain function. Inhibiting the difference effectively catches asynchronous disturbances in the EEG, but misses excess coherent activity. If we set inhibits on the sum, then we can more effectively catch and inhibit the abnormal synchronous activity. Just as rewarding the difference is usually the better choice, inhibiting the sum is likely to be the more important piece. Actually we are now choosing to inhibit on both the sum and the difference so as to detect both types of abnormal activity. The new EEG 2-Channel Sum and Difference with High and Low Inhibits settings file allow this on the BrainMaster. The two channels can be referential or bipolar, but it is important to keep the active and reference electrodes arranged similarly for both channels. For example we might use channel 1 active = C3, reference = T3, and channel 2 active = C4, reference = T4. Or with a referential hookup, channel 1 active = T3, reference = A1, and channel 2 active = T4, reference = A2.

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