Modifications for larger rodents?

[Vyash]

Hello all! 

I was wondering if anyone has tried modifying the FED for use in larger rodents such as rats? Specifically, I don't know if the photogates used would be tall enough to accommodate a larger snout size. Perhaps there is an alternative part that can be used for this purpose?

Also, I noticed that only the STL files are available on GitHub - I can modify on top of that to enlarge the nose-poke holes as necessary, but are the original 3D files (Solidworks, Inventor, or whatever other 3D program that was used) available elsewhere? That would make modifications much easier to work with.

Thanks for the amazing design, and I look forward to playing with it further!

[Kevin Myers]

Hi Vyash and everyone. A while ago I did quite a bit of tinkering to modify the FED design for rats and it ended up being much more challenging than first I expected. There were two main challenges: First, like you said, the nose-poke holes are too small for rats. But the nose-poke holes are sized based on the dimensions of the Sparkfun IR photointerrupter, which does not come in a larger size.  Increasing the inner diameter of the nose poke holes thus requires either physically cutting apart the two arms of the IR photointerruptor (which tremendously complicates the assembly, in terms of getting the two halves soldered into the circuit board via jumper wires so you can insert each half into the front housing before the board is installed) or using something like these which also requires physical redesign of the 3d printed front of the FED and some complexity at assembly. Second, it's a problem if you want to use 45 mg pellets which are standard for rats instead of the 20 mg pellets. This also required more extensive redesign of the pellet delivery apparatus than I initially thought.  I first thought all I'd need to do is change the thickness and hole size of the pellet disk inside the hopper, but actually the chute the pellets drop through is too narrow for 45 mg pellets, and it also requires modifying the nose piece (which you absolutely want printed in metal if a rat is getting anywhere near it!) since a 45 mg pellet will not fit into the slot in the nose piece where pellet delivery is detected.  Also I felt with the scaled up size of the nose pokes, it sort of blocks the visibility of the LED strip.

So anyway, my original goal was to make a rat version that required the minimum possible changes to Lex's original design. After working on it for quite a while I did get a working unit (see pic), but came to the conclusion that starting from scratch with complete redesign of the housing would yield something much easier to assemble. It has remained on my to-do list but I'd love to hear if anyone else has made an attempt at this.

Take care,

Kevin

--

Kevin Myers

Professor of Psychology
Bucknell University
Lewisburg, PA 17837
(570) 577-3493

kmy...@bucknell.edu

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[Lex Kravitz]

Hi Vyash!  And thanks for the info and updates Kevin that's super cool! 

The 3D designs were made in TinkerCAD and editable files are available here:

https://www.tinkercad.com/things/0QaiVw7KR3Y

Please post back if you have any success with making a rat version! 

[Vyash]

Thanks Kevin and Lex! I'll take a look and see what I can do.

Kevin, just out of curiosity, approximately what size were the rats that you were using? What was the diameter of the port you ended up using? I can remake the front piece in the next few weeks with mounting points for the IR break beam sensor that you linked. Unfortunately I won't be able to test anything until the other components arrive, but I'll let you know when things start to come together.

-Vyash

[Lex Kravitz]

I'll also throw out that the PCB design files are on the Github, they were made in Eagle.  I'm happy to help with PCB modifications too if you need help with this, but you should be able to substitute the photointerrupters we used for the IR beam sensor Kevin suggested, soldering right into the points outlined in red on the PCB:

-Lex

[Lex Kravitz]

To re-up this topic, I came up with an idea for a very simple modification to use FED3 with rats.  I am really curious if anyone is able to try this out, I don't have rats in our lab.

I think the main issue with using it with rats is not so much the size of the nose-pokes as the size of the pellet well, which I think is too small for rats to get the pellet out easily.  However, the pellet well part is not critical, it can be removed and FED3 will still detect when a pellet drops (it will basically conclude it was dispensed and removed immediately as it passes through the pellet well).  In this configuration FED3 can no longer detect the time that the pellet was removed by the animal, but that may be OK depending on the experimental goals.

I am attaching a video of FED3 operating without the pellet well that I made for someone who inquired about this, but thought it was worth posting here too.  If anyone can try this out with a rat please post feedback!

[Lex Kravitz]

Here's the video!

[David Haggerty]

Hi Lex, 

I’ve actually been thinking about a re-designed pellet well for mice to allow the pooling of pellets below the beam break in attempt to replicate some of our habit tasks from the med-associates boxes. Glad to know that the beam break will count the pellet as it passes by. Do you think that designing some sort of cup or bowl that sticks out in front of the light bar would be possible? I can take a stab at it if the nose piece files are on tinkercad?

On Jun 15, 2021, at 9:57 PM, Lex Kravitz <lex.k...@gmail.com> wrote:

Here's the video!

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<Fed3 For Rats-2.mp4>

[Matias Andina]

Hi all,

If somebody wants to redesign using the solid instead of the stl on tinkercad, we are about to submit the solid files for all versions since july soon to the github repository (before the end of the week).

Best,

Matias

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[Lex Kravitz]

Hi David! Yes redesigning the to add a little dish is pretty simple in TinkerCAD.  See an example here - looks like he is sticking it his tongue! 

I guess it could be used for dispensing 1 vs. 2 pellets this way too, that might be useful.  

[Lex Kravitz]

Thanks Matias for making those and putting them online!!

[Kevin Myers]

Hi everybody.  In my experience in tinkering with the rat-usability for the FED3, one thing I learned is the feeder chute cannot accommodate 45mg pellets which are typical for rats, so one would need to stick to using the 20mg mouse-sized pellets (at least that was true in the housing design as of 2018. I know you've done some redesign since then). Next time I'm in the lab I'll get out the digital calipers to take some rat snout measurements. I think the IR beam break sensors could probably work fine for younger rats but might be a tight squeeze for adult males.  I'll let you know what I come up with.

Kevin

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[Alison Kreisler]

Anyone have updates on modifications for adult rats? I just found this device/group and read through this thread, but it appears it's been latent for 9 months or so. Has anyone actually tried it in rats? 

[Gwenaëlle Le Pen]

Hi everybody,

I would be very interested to use FED3 in rats. Has anyone made and tested a rat prototype?

Thanks.

Best R.

Gwen

[Kevin Myers]

Hi everyone, happy new year.  Alison and Gwen thanks for reviving this question.  I did continue to tinker with modifications for a rat adaptation that I mentioned early on in this same thread a couple years ago. I eventually had a complete redesign of the whole device (on paper, at least) that moves away from a 3-d printed housing for the sake of physical robustness against rats, instead mounting the electronics into standard sized electrical junction boxes (for example). The design would have had a steel face plate custom laser-cut by SendCutSend*, with a 3d printed pellet well/dispenser assembly mounted on top of the metal box through one of the pre-punched cutouts. The aim was for DIY assembly (since I was always enamored with Lex's original approach of designing something any lab could build with mostly off-the-shelf parts). I stopped when I reached the point the best next step would be to modify the physical layout of the circuit board, and when paused at that point, I then learned (and this is probably the answer to your actual question...) from Claire Foldi at Monash that she and her group have had good success using the current mouse FED3 device for rats. Specifically, females SD rats up to ~15 weeks old, I believe she said.  A few caveats:  #1, the standard FED3 can only accommodate 20mg pellets, not the 45 mg pellets more commonly used with rats, and Claire said they do use 20mg and rats actually learn quickly and you get a lot of behavior for the 20mg pellets because rats are not getting quickly satiated. #2, at the start, baiting the nose poke wells with sucrose pellets helps them learn the task. #3 very important is to glue metal washers (this is a good size) on the front of the nose-poke ports to deter rats from chewing up the plastic face (you also want the nose piece that the pellet drops into printed in brass or other metal).  

I don't want to speak for Claire (who I think may be in this group) but I can confirm I assembled one recently and tested it with a couple young adult female rats (9-10 weeks old, ~200 g) successfully.

Hope this is useful info!

Kevin

*tangentially- just a plug from a satisfied customer. If you ever need laser cut metal parts or very large acrylic parts I've been thrilled with SendCutSend. I had a Barnes maze top and a few other small pieces made and the prices and customer service are amazing. If you need a few metal parts laser cut they can often make it for less $ than the typical retail price you'd pay yourself just for the the materials. I don't know how they manage that but I'm willing to believe there's magic involved.

[Alison Kreisler]

Thanks so much Kevin! This is super timely as I was JUST about to start my own pilot attempts with rats + FED3. For the pellet drop piece adjustment, how do you/Claire recommend printing those in metal? With FED3 or SendCutSend? Can this piece be done independently from the rest of the device and then replaced? I already purchased several complete FED3 units. 

If I can get these adjustments in time, I will give it a go with older females, since that's what we have at the moment, to confirm if there is a body size cutoff. 

[Kevin Myers]

Alison, Yes - just the small nose-piece that inserts into the front to catch the pellet when its dispensed -- you can have just that part 3d printed in metal by many professional 3d printing services.  Shapeways is one of the main companies that a lot of FED3 users have used for this. I believe they're fairly competitive price-wise too.  (If your university has good professional shop facilities they may have the capability to do it. Many high-end/industrial grade 3d printers do have the ability to 3d print metal pieces, though this is beyond the capability of your typical hobbyist/consumer/lab 3d printer)

I've attached a copy of the STL file of the specific part that needs to be printed in metal, and bronze or steel is recommended I believe (Lex, please chime in if this file is not the most up to date version or if there's newer advice on this step).  With this file you can get an online quote from Shapeways or any other major service.

Good luck!

Kevin

[Lex Kravitz]

Thanks for the advice Kevin!  Yes that's the correct STL.  I made a shop on Shapeways to make it easy for people to order parts.  I don't receive any proceeds from the shop BTW, it's just an way easy way for people to order these designs from Shapeways.  Shapeways has great quality but they are a bit pricier than other options.  Their price for this little nosepiece in steel increased from $15 to $30 over the last 2 years! 

I've also used a cheaper company in China called WeNext, we've had good results with them but I don't think their quality control is as stringent as Shapeways.  They also offer steel printing. 

Please post back with your results from rats!

[Alison Kreisler]

It appears that some of our adult female rats can indeed remove the 20mg pellet from the FED3. We're going to keep trying to get a better sense of how easy it is. Does anyone have any suggestions for stabilizing the device within a standard rat cage (plastic tub)? The adult rats are capable of tipping it and moving it around the cage, especially if removing the pellet is difficult. 

[Lex]

Cool thanks for the update!  

One idea could be to glue a strong magnet (like this) inside the bottom panel of FED3, and then stick a cell phone magnet plate to the bottom of your box.  We have done this to stabilize FED3 on a plastic plate - not sure how strong your rats but there is room inside FED3 for a big magnet :)

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