Do chickens go brain dead at night?

They do go into a deeper state of sleep, that is why a lot of people recommend picking up hard to catch chickens off of the roost at night rather than chasing them around during the day.  Its also why they are so extra vulnerable to attack at night.  They also have worse night vision than us, I have found.

Yes, they do. LOL
Seriously, it does seem that way, doesn't it? I don't think simply being unable to see in the dark explains it either!  I don't care how dead dark it is, if something grabs ME I will be screaming and flailing. Chickens just sit there. What IS up with that?

Actually, as a preventive measure most birds go into less of a deep sleep as compared to most mammals as a means to avoid predators.  The fight or flight mechanism will kick in if scared and I have had birds flee aimlessly from the perch if startled.  The reason birds act lethargic at night is because they are not designed to see well in the dark  With the exception of owls, birds in general do not see well at night at all and therefore they generally get on the perches before it gets dark and settle in for the night.  If you observe them at night they are actually not in a deep sleep but open their eyes periodically to 'check things out'.

I call them "Zombie Chickens." It's weird how they just go limp.

This is an interesting point.  But I don't think this light sleep state is true of all birds all the time.  Here is an good link if you want to learn more about partial awareness during sleep:  http://www.sciencenews.org/sn_arc99/2_6_99/fob5.htm

I have noticed that the my ducks and geese seem easier to wake than roosting chickens  (the water fowl also have better night vision than chickens).  But I have noticed when chickens can be woken they can startle and flap and run off.  I have read that other birds like the hummingbird actually do go into a stupor and their body temp falls a lot, so I guess it depends on the type of bird.

They're also nearly blind in the dark.

I have no idea what kind of sleep they go into but after years of keeping fairly wild guineas, peafowl and chickens, I've learned that it's incredibly easy to pluck them off the roost or out of a tree once it's completely dark outside. Even the wild ones will let me go right up to them and grab them. The wilder ones will squawk like they've been caught by a predator once I've caught them so they do wake up. I usually use a flashlight but keep the light pointing downwards.
I recently had to catch a bunch of my chciken's who had decided they wanted to roost high up in the lemon and pine trees. I used this method and climbed up with a ladder. The Egyptians, silver leghorns and Hamburgs were not getting caught any other way. I locked them all in the coop and clipped their wings so they would have to relearn where their roost is.

Here is an interesting article on how chickens see.  It appears they have better color vision than us but worse night vision (which we know)

http://www.livescience.com/8099-chickens-color-humans.html

I was just thinking about the same thing. My polish hen has taken to roosting on the fence between our yard and the run, and when it comes time to move her into the coop she seems practically comatose and I have to kind of balance her on the roost.
She's exceptionally gifted in the crest department, so I guess it makes sense that she just can't see well enough to figure out the roost by herself.