"What I’d really like to see is a study monitoring the brain activity of rattlesnakes carrying out maternal care tasks and comparing it to brain activity during activities such as “kissing” when interacting with handlers. Would the same regions of the brain light up? How would the results then compare to acts of affection in birds or mammals? But the biggest question is; who would pay for such research?"
Yo, I absolutely would, let's get a kickstarter going

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Honestly, I think a bigger question is how you would get a rattlesnake to engage in maternal care tasks while in a functional MRI scan. You'd then have to get in there with it and let it kiss you, no fair using some other species of snake.
I all seriousness, good on you for researching, and if you stumble across anything free you can link to for those of us outside the ivory tower, please do! I was actually trying to read about the limbic system of reptiles earlier today because of this thread.
Excerpts and price tags. Boo.