Jimmy Dooley

Of course, the full paper has more details (oscillations, state transitions, developmental timing, behavioral correlates, etc.) but these are the main highlights.

Happy to answer questions - and stay tuned for more about how sleep states shape early motor development!
12/end

The broader point:

Infant REM isn’t a tiny version of adult REM.

It’s a developing state that gains new structure over time - and this new structure likely changes the plasticity that’s possible during REM sleep.

“Sleep like a baby” turns out to be…a lot more complicated than we thought.
11/x

So why does this matter?

Because REM sleep isn’t just “sleep.”

It’s a major driver of early sensorimotor development.

By showing how tonic REM emerges (and becomes distinct from phasic REM) we can start to understand what neural representations are even possible in the developing brain.
10/x

So here’s the key result:

At P12, REM doesn’t have two substates - it’s one undifferentiated state. The two-stage structure of adult REM just doesn’t exist yet

That two-stage structure emerges during the 3rd postnatal week via a progression that looks a bit like the development of NREM sleep
9/x

Meanwhile, phasic REM keeps looking like the REM seen in early infancy, complete with:
• High neural activity
• Frequent twitches
• Elevated gamma

And by P20, phasic REM also has theta oscillations
8/x

Importantly, tonic REM doesn't just appear, fully formed. Instead, its features appear one-by-one

At P16, early REM bouts are mostly twitch free

At P20, tonic REM has slower theta oscillations than phasic REM

At P24, the alpha rhythm characteristic of tonic REM first appears
7/x

From P16–P24, this starts to change.

REM bouts start to start to show a predictable pattern:
a low twitch rate at the start, with twitches becoming more likely as the bout moves on.

This pattern becomes more reliable with age - by P24, it looks a lot like adults.
6/x

Looking at all REM bouts at once, at P12, REM is basically one big noisy chunk of time. Lots of twitches, lots of movement, and occasional (but brief) twitch-free pauses.

But those pauses aren’t tonic REM. They lack the oscillations, structure, and sequence that define tonic REM in adults.
5/x

That’s the central question.
From postnatal day 12–24 in rats (roughly early → late infancy) we asked:

How does REM sleep go from a chaotic twitch-fest into the ordered tonic → phasic REM we see in adults?

First, we noticed that the time to first twitch (blue box) got longer as pups aged.
4/x

In particular, in adults, REM sleep - the wake-like, dreamy sleep state - has two substates:

Tonic REM (REM without eye or body movements)
Phasic REM (REM with movement)

But we didn’t know when or how these substates emerge in infancy.

(image from Boscher et al., 2024)
3/x

Most people know babies sleep a lot.

But fewer know that infant sleep isn’t just “adult sleep but shorter.”

Infant sleep has its own rules, rhythms, and states. And critically, many of the states that we see in adults don’t exist yet in newborns.

(Image: Blumberg, Dooley and Tiriac, 2022)

2/x

Creepy art from the middle ages showing a baby as a tiny adult

New preprint!
www.biorxiv.org/content/10.1...

You've heard the phrase “sleep like a baby” - but what does it actually mean?

Turns out, infant sleep is way different from adult sleep. And we still don’t understand the journey from infancy to adulthood.

tl;dr babies are not just tiny adults

1/x

Data gods be willing 🤞🤞🤞

I was just thinking about this because I posted a new paper on biorxiv yesterday - and thought "what if I have papers go live on Thanksgiving 2 years in a row"

id say worth it - but my share of the spam burden seems to be a bit lower...

It's great seeing a list thats half full of books you loved - and half full of books you haven't read - yet!

They did more than compare these two species - they crossed them!

Super super cool sounding paper that must've been an unimaginable amount of work

I've got to say this is one of the COOLEST sounding papers I've seen in over a year! I skimmed the figures last night and can't wait for a proper read through soon

What an amazingly cool project!

I think the fact that this post is resonating so strongly says something very important about present-day academia.

Just had a DM convo with Mike about it - we've both had people tell us "your postdoc is your best stage in academia" - an idea we agree with (but wish wasn't the case...)

An argument always worth repeating.

@marksblumberg.bsky.social

I read this entire thread in your voice.

guess they're pulling out everything to get to 100% of spending

If you are funded by NIMH and only received 85% of your budget this year (like we did), check era commons to see if you have a new award notice. We just got the remaining 15% today.

Two years of (non-federal!) funding for the lab! Should be able to fund science and (nearly) all salaries in that time. I guess people weren't lying - you need at least 10 rejections before the funding gods give you a win.

Done!

Look what just moved to the top of our labs summer journal club reading list.

Can't wait to take a look! So far, gorgeous visuals!

We argue that instead of focusing on when in development "REM sleep" can be unambiguously called REM sleep, we should focus on how these REM sleep features map onto REM sleep functions. Understanding the relationships of features to functions is a key part of the next decade of sleep science.

Basically, REM sleep (as it's defined in adults) has a bunch of components, or features, that all develop at their own rate. Gao et al.'s recent publication (Ontogenetic development of PGO waves during paradoxical sleep in kittens) shows us that PGO waves are the last of these features to show up

Building the dream: uncovering the development of REM sleep’s features Imagine a factory that builds cars. Raw materials come in one end, the individual components are progressively assembled, and complete cars come out the ot

An editorial from the lab was published today about a recent paper published in the journal Sleep that characterizes the development of PGO waves. It's short, so if you have ~5 minutes, go ahead and click through. Still, a quick summary in the 🧵 that follows.

academic.oup.com/sleep/articl...

Part of me thinks a piece of the problem is data analysis is so (relatively) easy now

I know some of this is survivor bias but I'm amazed at the depth of the theory (given the limited data) in the 60s and 70s classics

If analysis was still done by hand we'd think a lot more deeply before analyzing

Sky's are likely turning colors tonight. If you're in the Midwest, you should have cloudless sky's tonight - take a look at 10-11pm. And even if you can't see anything, point your phone to the northern skies, just in case