I dont understand what you mean by taper off. This paper might be of interest: http://dx.doi.org/10.5665/sleep.3138

They count high amplitude slow waves during wake in rodents and find that they occur more often with increasing sleep pressure. The idea is that these correspond to the sleep-like off states that occur during wake when sleep deprived, as has been shown by Vlad Vyazovskiy.

I didnt have much success with this measure in rodent EEG, though. Small movement artifacts occur preferentially in the slow wave range, which confounded my wave-detection.

This is an important research question which is currently under investigation and (as far as I know) there are no published reports. However, the theta band is chosen in those studies because it is the frequency band that shows the most amount of change related to prolonged time awake. I do know from unpublished data that there are some small general increases in lower frequency ranges (1-5Hz) during wakefulness, but these are usually not signficant and may be caused by artifacts related to sleepiness (such as increased blinking).

Dear Lars,

Thanks for your information.  Let me elaborate on 'taper off'.  I classify low frequency oscillations in the noninvasive human EEG in frequency space, because they are really hard to count and measure out in the signal.  In frequency space the beginning and end of the 'physiological' frequency bands are not very well defined, not even for the Berger alpha waves.  My question is what are the limits of the frequency bands related to sleepiness.

The article you cited is incredibly helpful in this regard.  Thanks.

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Dear Armand,

thanks to you as well.  It's good to know that I'm not the only one that is bothered by the low-frequency wake EEG.   Eye blinks are indeed a problem, which is why I do most of my preprocessing by hand.  However,  the blink rate does not necessarily increase with sleepiness (see Ref.).

Best Regards,  Justus

Article Eye Spontaneous eye blink rates and dopaminergic systems