Hi,

While we have a normal night sleep, NREM is more frequent during the first half of the night and REM is more frequent during the second half. Thus, if the experiment tests the influence of REM sleep, the subjects may be sleep deprived, starting from 3 AM for example. I would like to know, what happens, when sleep schedule changes abruptly. For example, suppose somebody goes to sleep every day at 10 PM and wakes up at 6 AM, but one day he changes sleeping hours to 3 PM – 11 PM. I would expect, that his NREM and REM stages order remain the same (just start 5 hours later). However, as far as I could understand from different experiments in the following review: GÉRALDINE RAUCHS, BÉATRICE DESGRANGES, JEAN FORET, FRANCIS EUSTACHE (2005)
The relationships between memory systems and sleep stages
Journal of Sleep Research 14 (2), 123–140.
doi:10.1111/j.1365-2869.2005.00450.x
the stages are constant and this person will get REM stage at 3 PM in any case. So, what stage will he get then at 10 AM, when he is awake? What happens then to person after large jet-legs?

Thanks for help!

Vadim

if you shift your sleep-wake cycle, your REM and NREM also get shifted. I don't see what the misunderstanding is.

Also, with sleep deprivation, the participant will enter REM sleep quicker when longer period of deprived sleep goes on. So say the first night you interrupt their sleep pattern just before they enter REM sleep. The second night your interrupt their sleep patter just before they enter REM sleep and so on. The next night, they will enter REM sleep #quicker#, almost like they are making up for 'lost REM time.' Also, REM is important for memory consolidation.

Sleep is triggered by a zeitgeber. Light is often the dominant cue of when to go and when to wake from sleep. With jet lag, a disruption of circadian rhythms due to cross time zones occur. These problems of sleepiness stem from the mismatch between internal circadian clock and the external time and zeitgeber of light. Some individuals react more violently to jet lag. This increases stress levels, which increase the hormone cortisol, and prolonged cortisol can lead to a loss of neurons in the hippocampus (used for consolidation during sleep). So, if you often experience jet lag (flight attendants, pilots, cross-seas travelers, etc...) often, stress levels increase because of these reasons; this results in lower hippocampal volume (shown in studies that have examined flight attendants).

So, in your example of this person just adjusting their sleep schedule for one day, nothing much would happen. The person would probably just be groggy. Nothing major. However, if s/he often disrupts their sleep schedule l, then the above may occur.

Ok. Thank you.
According to what you are saying, whenever I will permit the subject to sleep, he will start his standard sleep stages order (if we are talking about only one night experiment). Suppose I want to verify, which sleep phase is more important in procedural memory consolidation. From REM stage the subject can be easily deprived by awaking him at the miidle of the night. But what about NREM? I can't deprive from half night sleep, since the REM stage will not come before the NREM. So, the only way will be to awake the subject every time he enters the NREM (SWS) phase. But this procedure introduces additonal noise to the experiment. Is there a workaround?

Vadim, each NREM phase has special EEG markers of what phase the participant is in.
Example- NREM Stages
Stage 1 = EEG is full of short, rapid, choppy waves.
Stage 2 = sleep spindles (12-14 Hz waves during burst that lasts half second) and K-complex (sharp, high amplitude wave) appear
Stage 3 = slow-wave sleep. Lower frequency waves (hard to distinguish from stage 4)
Stage 4 = appears like stage 3, a bit slower frequency waves, though.

All of these stage characteristics are averages of participants. These are not solid markers of these sleep stages, but most likely they will appear in these stages.
So, if you wanted to see what stage was (most) important for consolidation of procedural memory, you'd have to hook the participant up to an EEG to get a sense of what stage they are in. You would need to do this over several nights and test procedural memory from, say, a lack of stage 3 sleep for 2 days or whatever.
After about an hour of sleep, the person starts to cycle back through from stage 4 through stage 3, 2, and then REM.
This sequence repeats about every 90 minutes.
So, a 7 or 8 hour sleep will produce about 3 to 4 cycles of this 1, 2, 3, 4, REM, 4, 3, 2 cycle

This varies from person to person, however. ** Technically, if the participant goes through 1 round of REM, it does come before subsequent NREM phases. However, this creates noise like you said. Right off the top of my head, I don't have a work-around. Do a search of the literature, and see if there are any journal articles relevant to your hypothesis. They may have done a version of the experiment that you are suggesting, and they may have possibly found a way around this extra noise. (?)

Thank you lcsglvr for detailed reply.