Talk:Phase response curve

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The term 'acrophase' is ambiguous here with respect to the illustration. It could either refer to the hormone level that triggers the precipitous climb from delay to advance, or it could refer to the hump over the van in the diagram legend 'advance'. I was unable to confidently map the textual description to the diagram in less than a minute of hard thinking. MaxEnt 18:30, 25 June 2007 (UTC)

I'm wondering if the article could be improved by just not using the word "acrophase" at all. Anyone new to the concept of a PRC is going to find it confusing enough. It's fine that the curve is described as sigmoidal, an S-curve, as that is well-known. "Acrophase" apparently just means the peak and the nadir of such a curve. Why not just call it that. I'll attempt a bit of rewriting. I won't be insulted if it's reverted, as I just barely understand this stuff myself. Hordaland 19:43, 16 September 2007 (UTC)

Good PRC reference diagram

• How to Trick Mother Nature into Letting You Fly Around or Stay Up All Night

- free full text, see p.354 with full PRC diagram for both light and melatonin

MaxEnt 13:36, 27 June 2007 (UTC)

• I've been looking for an image of the PRC for melatonin, and not found one. Your link only allows me to see the abstract, not the full text. Any way to see full text without being a subscriber to something-or-other?? Thanks. Hordaland 11:31, 8 July 2007 (UTC)

Today I discover this article has disappeared behind a subscriber wall since I posted the previous remark. It was free not long ago, I viewed it a number of times. MaxEnt 16:29, 18 July 2007 (UTC)

From my personal wiki, I cobbled two sentences to self from this article before the coin-op door slammed shut, pertaining to the advance portion of the PRC:

Assuming an 8h sleep interval, rising at 08:00, the melatonin has half max response at 15:00 and 21:00 and full response at 17:00. In this diagram the light PRC flips at 04:00 (shortly after body temp. min. at 03:30) which is more consistent with a baseline sleep of six hours and an 06:00 rising time in other studies.

Several assumptions are built into this representation: body temp. min. 2 hours before waking, DLMO two hours before bedtime. The studies I encountered never made it clear whether min. body temp. or DLMO was the more reliable phase marker relative to the melatonin PRC in the case where these markers are not in a typical phase relationship. MaxEnt 17:17, 18 July 2007 (UTC)

• Thanks. There are indeed many unclear points and many assumptions. Different studies use different formulations of melatonin, different dosages and different ways to measure DLMO, when they even measure it. Temp.nadir is particularly illusive; I've seen that it can vary individually from 1 to 6,5 hrs before spontaneous awakening, with (in one study) female nadir averaging a half-hour earlier than male.

The one PRC for exogenous melatonin which I finally found for my blog, http://blog.360.yahoo.com/blog-EkVtCKc_dqe59aJ1wEY-?cq=1&p=132 , (from 1996!) shows, assuming wake-up = 8 a.m., maximum advance at about 4:30 p.m. and DLMO at about 9-10 p.m. Not too far off your "note to self". Hordaland 14:34, 19 July 2007 (UTC)

At the time of writing this, there's free access to the paper, "How to Trick Mother Nature into Letting You Fly Around or Stay Up All Night" here: http://www.chronotherapeutics.org/docs/other/Revell%202005.pdf And there's a lovely "Human Phase Response Curves to Bright Light and Melatonin" graph on its pg 2. Don't know anything about copyright though. Hope this might help somehow. — Preceding unsigned comment added by 109.153.85.226 (talk) 18:16, 23 March 2012 (UTC)

Light therapy after spontanous awakening

The article talks about how the window for sleep phase advancement is 4 hours total (2 hours before and 2 hours after spontaneous awakening) and that the best time to try it is after spontaneous awakening. However this article on teens and sleep cycles recommended using light therapy 2 hours before natural awakening time.

http://www.sciencedaily.com/videos/2006/0201-waking_up_teens.htm

It seems doing it 2 hours before could be counterproductive, if you are off by an hour in the wrong direction it might cause a sleep delay instead of sleep advancement. Either way, I'm not sure if doing light therapy at spontanerous awakening is considered the de facto best time for sleep advancement light therapy. unsigned comment added by 71.171.254.177 (talk) 03:33, 3 September 2010 (UTC)

Better Light PRC Needed

Hey thanks for all the recent edits Hordaland, the article is looking a lot better. I noticed that the article is still using the ugly PRC for light I made a while back. I put it in there because the article needed one but I couldn't find a good free one online. I tried to make it in accordance with the literature but also simple enough for most people to understand (hence the use of the vague terms on the x-axis instead of circadian time). Also, I remember from class that humans have a much easier time delaying than advancing in response to light but I forget if that is due to the maximum phase shift per day being greater for delays than for advances, or due to the fact that it is just easier to stay up late than to get up early. If the difference is due to the maximum phase shift for delays being greater than that for advances, then the graph should reflect that. At any rate, if someone is able, it would be greatly appreciated if they could make a more visually appealing (and perhaps more accurate?) PRC for light. I would do it myself but unfortunately the current version represents the pinnacle of my artistic ability. Nathanaver 21:59, 3 November 2007 (UTC)

Thanks for your kind words! I've not been at Wikipedia for long, and I'm not a scientist nor terribly computer-wise, so I held my breath about what response I'd get here (and on the new article I just wrote, Chronotype). My main point in editing the PRC article was to try to explain what it's for, why it was invented in the first place.

As to the drawing of PRC for light, I have two in my own blog. I drew them both myself (in Paint), and I'm no artist either: http://blog.360.yahoo.com/blog-EkVtCKc_dqe59aJ1wEY-?cq=1&p=36 and http://blog.360.yahoo.com/blog-EkVtCKc_dqe59aJ1wEY-?cq=1&p=37 (there must be a prettier way to link here...). In one of them I also used vague terms on the x-axis, which is plenty good enough for the reasons you state. Sources for both of them, both gif, are linked in the accompanying blog entries. I also have done a drawing of PRC for melatonin http://blog.360.yahoo.com/blog-EkVtCKc_dqe59aJ1wEY-?cq=1&p=132 which I'm less satisfied with. There I used "circadian time" without really understanding what I'm talking about, I fear...

The reason for delaying being easier than advancing for almost all humans is that our intrinsic period is a bit longer than 24 hours. I'm not sure what you mean by "the maximum phase shift for delays being greater than that for advances" as that depends on timing and light intensity. But perhaps it does make sense, as almost all of us would delay just a tad daily if there were no outside input at all. As I explain to my illustration borrowed from Harvard, "The horizontal line, about a half an hour below zero, shows how great the delay would have been anyway during the course of the experiment, due to the built-in pacemaker's longer-than-24-hour period, had there been no light exposure at all." Hordaland 15:09, 4 November 2007 (UTC)

Oh, I like that first one with both bright and dim light on it. I don't know if you wanted to donate it to WP or not, but if you did I think it is a step up from mine in the aesthetics department plus it illustrates an additional concept.

I just meant that for a given light intensity and assuming ideal timing in each case, the maximum advance achievable will be less than the maximum delay achievable. That may or may not be true and based on your graphs it looks like the opposite might be true. So anyway, just ignore that, I think I might have been making stuff up again.

I forgot to take the free-running period into account, of course that would account for the fact that it is easier to delay than advance. Funny cause those cave experiments are some of my favorites yet I still forget the important implications of them. Nathanaver 22:09, 4 November 2007 (UTC)

Wikipedia is welcome to my drawing, if that's legal (it is just copied from the original). Or one could contact the right people about using the original. Computer challenged as I am, I'd rather send my "HumanPRC.bmp (719 kB)" to someone to be converted/uploaded. Need only an e-mail address. Hordaland 23:36, 4 November 2007 (UTC)

Need to generalize the article

Phase response curve can be applied to any oscillatory system to describe how a perturbation changes the phase of the oscillation. I do not know the history of the terminology, but it would be nice if someone can fill that up. In physics and computational neuroscience, there have been quite a bit of work for PRCs. Memming (talk) 13:29, 12 August 2008 (UTC)

Interesting comment, thanks. It would be interesting to know when/where the term first was used. I've only seen PRCs in regard to biological circadian rhythms, probably because that's where I've looked for them :-). Here is a source for other areas of use. I don't know if it is allowable here, but it's sources may be. --Hordaland (talk) 16:25, 12 August 2008 (UTC)

Yes, that scholarpedia article is a good example. Perhaps, I can asks some of my physicist friends to put some mathematical details to this article. :) --Memming (talk) 14:13, 17 August 2008 (UTC)

It was I who credited Dr. DeCoursey with "inventing" the PRC in 1960, sourced to ScienceBlogs -- which, thankfully, no one has argued with. But I meant, of course, the use of the PRC as a tool in chronobiology. I hope you find out more about it in other fields; that would be interesting. --Hordaland (talk) 19:05, 17 August 2008 (UTC)

Top image

I want to use this image at the top of this page but I'm not sure how to upload it or whether copyright issues allow me to do so. If anyone else is willing to look at this I'd appreciate it.Docfaust (talk) 20:25, 30 April 2011 (UTC)

Mish-mash unlove

I've long thought this page was too much of a mish-mash. Looking at it now, I'm tempted to factor out the chronobiology to a page titled chronobiotic phase response curve or chronobiotic PRC (I'm tempted to let the former redirect to the latter).

This is the kind of mish-mash that earns an article the long-term cold editorial shoulder. It's so disorganized and awkwardly straddled, one is reluctant to dive in for a quick edit, and with no quick edits, substantive edits rarely follow. — MaxEnt 02:10, 16 March 2017 (UTC)

Mathematical material

I've reverted the extensive math that has been added to the page. I think it needs to be clarified whether this satisfies WP:NOR and WP:NOTESSAY. --Tryptofish (talk) 23:31, 26 December 2018 (UTC)