Not the gravity can have effect onto the EEG rhythms and sleep stages... The changing of the gravity field...

Dear Mr. László-Attila Horváth,

Why? -----  It is just a idea!

Do you have any article to reject of this title?

Best  Regards.

Dear Seyed, this is a very interesting question not for the already studied and known phenomena related to the sleep/awake changing regime but I think for a series of "second" order phenomena that could be very interesting to investigate on EEG traces acquired in weak or without gravity conditions (and at a suitable time resolution).

Mr. Moradi,

That is an interesting question and can be interpreted in several different ways. For example effect of gravity on EEG when you are at sea level or when on top of a mountain or high altitude. You may wish to know the effect of gravity on EEG during space travel. Alternatively you may have an interest in EEG activity when the human body is subjected to hypergravity as in parabolic flight. Since you have not given much detail I think you might like to look at the following papers

Artificial gravity results in changes in frontal lobe activity measured by EEG tomographyOriginal Research Article: Brain Research, Volume 1285, 18 August 2009, Pages 119-126

by Stefan Schneider et al

and also the paper

Degraded EEG response of the human brain in function of gravity levels by the method of chaotic attractor: Acta Astronautica, Volume 52, Issue 7, April 2003, Pages 581-589

By Vladimir Pletser & Olga Quadens

But if you think changes in gravity due to day-night variations may influence EEG, then you may want to look at the paper

Day–night variations in plasma melatonin and arginine vasotocin concentrations in chronically cannulated flounder: Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, Volume 130, Issue 4, November 2001, Pages 827–834

by Kulczykowska et al

they measured melatonin changes and found some differences between night and day.

Since melatonin is mainly produced by pineal gland in the centre of the brain then that might have some influence on EEG.

I hope this helps and when you find out more you let me know.