Animals coordinate groups of muscles — like arms and legs — to move. Coordination develops. A newborn baby is basically luggage; she stays where she’s put. 2/25pic.twitter.com/jCB8C2QzjZ
Show this thread
Would you believe baby fish can teach us how movement develops? Amazingly, we found that a sense of balance is KEY. Come see why in this thread! 1/25https://www.biorxiv.org/content/10.1101/538546v1 …
-
-
-
But a couple of years later, that same baby skillfully coordinates her arms, legs, and trunk to walk — even when posture is challenged & balancing is hard!
#prouddad 3/25pic.twitter.com/chTmNZ2V6BShow this thread -
David Ehrlich wanted to figure out how coordinated locomotion develops. Thanks to baby zebrafish, he figured out that the challenge of staying balanced is incredibly important. 4/25pic.twitter.com/IsJedp5sn8
Show this thread -
Before he could crack the development of coordination, he needed to understand the physics of vertical movement. Let’s think about how flying machines might go up. 5/25pic.twitter.com/OEK9xUbHKK
Show this thread -
Consider a rocket. A rocket goes where it is pointed. If you want it to go up, point it up & launch. If you want it to go up at an angle, well, you’ve got to change where its nose is pointed. 6/25pic.twitter.com/Pq7uC6MItl
Show this thread -
Now this is true for fish — they mostly go (Trajectory) where their nose is pointed (Posture). The diagonal line would be perfect Rocket Style, like in the movie. 7a/25pic.twitter.com/z2VaTQvIJa
Show this thread -
Check this movie out: the baby fish goes where its nose is pointed!pic.twitter.com/VkqnASZhpk
Show this thread -
But there’s another way to go up. A helicopter’s rotors generate lift, so it can go up without rotating it’s “body.” 8/25pic.twitter.com/zVIPzGha37
Show this thread -
How about a fish? Can baby fish climb without rotating their bodies?, Oh can they ever! 9a/25pic.twitter.com/u4wCZShZqg
Show this thread -
And check out those adorable fins! You're looking at a fish from behind, so the tail is pointing towards you and is slightly out of focus. 9b/25pic.twitter.com/USK6UxUZ7j
Show this thread -
Are the fins really generating lift? David checked. Without fins, baby fish go all Rocket Style. To climb, they have to change their posture. 10/25pic.twitter.com/bpBSSQ8HTU
Show this thread -
So baby fish use their fins to climb. But are they really -coordinating- their fin and body movements? Great question! David compared the body and fin movements to measure fin-body synergies, like so: 11/25pic.twitter.com/t8AgzIdJAX
Show this thread -
Instead of the No Synergy flat line he saw a strong relationship: the more baby fish rotate their bodies, the more they engage their fins. Do you want synergistic climbs? That’s how you get synergistic climbs. 12/25pic.twitter.com/d9LD2RSXaN
Show this thread -
Not only that, but check it out: the relationship between body and fins gets stronger as fish develop. Older fish (3 wpf = 3 weeks old) couple bigger fin movements w/smaller body rotations to climb. So older fish climb more stably… 13/25pic.twitter.com/fGTA4brETx
Show this thread -
Maybe. Is the nervous system really responsible for this “coordination?” David did two key experiments that revealed that yes, yes it is. 14/25pic.twitter.com/tsflOgAPGD
Show this thread -
First, he looked at mutant fish with broken inner ears. These baby fish can’t sense gravity’s pull. How do they climb? 15/25pic.twitter.com/eufJAf58QE
Show this thread -
Gravity-blind mutant fish make similar body and fin movements to their normal siblings. But look! The synergy David saw before is gone! This is a Big Deal because…. 16/25pic.twitter.com/oMW46jqggU
Show this thread -
If the mutants can’t coordinate, but otherwise swim normally, synergies don’t come from passive biomechanics. PLUS now David linked sensed balance (broken ears) to coordination (broken synergy). Super cool! 17/25pic.twitter.com/xSGdbJzvVu
Show this thread -
Next, David knew that the cerebellum (or “little brain”) coordinates movement. Guess what? Fish with a broken a cerebellum engage their fins too much (steep) — even when diving (LOL wut)! 18/25pic.twitter.com/tDazs55X72
Show this thread -
Once again, another Big Deal. The cerebellum is telling the fish when NOT to use its fins. David’s work on climbing offers a new way to understand this most important brain region. 19/25pic.twitter.com/xCRPLDqV9N
Show this thread -
So David showed how coordinated fin use facilitates balanced climbing (which gets better as fish develop). But is it really balance that defines the development of coordination? 20/25pic.twitter.com/w1izmKLlwa
Show this thread -
How much do fish care about balance? David reasoned that coordinating the fins and body would take effort. So he built a model to play effort against balance. 21/25pic.twitter.com/vHWXJb2dsm
Show this thread -
The model works well to recapitulate the features of climbing that David observed. 22/25pic.twitter.com/BWmDK7AiMx
Show this thread -
If fish try to minimize effort (because really, who wants to work hard?) then David could infer how much they cared about balance. As they get older, they value balanced climbing more. 23/25pic.twitter.com/b2NDJ8DasW
Show this thread -
So: 1. To climb, baby fish coordinate their fins & bodies (f&b) 2. Developing fish come to climb in a more balanced way 3. Gravity-blind fish don’t coordinate f&b 4. The cerebellum regulates f&b coordination 5. David modeled how the value of balance increases as fish grow 24/25
Show this thread -
Work was all done by David Ehrlich, Ph.D.
@nyulangone with support from@NIDCD and@HearingHealthFn. Thanks so much for reading! 25/25Show this thread -
Handy link to the preprint here: https://www.biorxiv.org/content/10.1101/538546v1 … Enjoy!
Show this thread
End of conversation
New conversation -
Loading seems to be taking a while.
Twitter may be over capacity or experiencing a momentary hiccup. Try again or visit Twitter Status for more information.