It has come to my attention recently that the last version released contains a dysfunctional script that failed to add a couple of the dog brains back to the player if they had defeated them in their save prior to adding this mod. I'm working on a newer version of this mod currently, but before then you can correct this problem by adding the brains with the console commands below.

Reyplayer.additem 0013D852 1
Lupaplayer.additem 0013D851 1 
Violettaplayer.additem 0013E5BA 1
GhashBone(M)player.additem XX000AE0 1 (where XX is my mods placement in your load order)
BoneGnash(D)player.additem XX000ADF 1 (where XX is my mods placement in your load order)
Cheyenneplayer.additem XX00280A 1 (where XX is my mods placement in your load order)

I believe this only occurs with the vanilla brains (Rey, Lupa, Violetta), but I've included the commands to add the brains of GhashBone (Marie), BoneGnash (Donnie), and Cheyenne as well. Just in case.



Update Log:

Update 0.62b 1/6/2016

-fixed an issue which prevented the mod from running after an update
-with that being said, if you've ever updated this mod, you need this update for it to run properly
-fixed a sound directory error that prevented voiced dialogued
-fixed the motor runner dialogue, there were no recordings prior to this, so dialogue must have been impossible to read
-as a side note, a lot of mod elements will reset upon updating (replaying messages and whatnot). don't be alarmed, this is normal, but will not happen again in future updates or any other of my mods for that matter, because I've learned from my mistake of changing the esm names from update to update


Update 0.61 12/28/2015

-cheyenne's brain is now available for use, added a little dialogue for sunny smiles(read more in the new brains section)
-fixed some quest condition errors in the motor-runner quest
-fixed some dialogue errors
-fixed some script conditions with the GhashBone perk quest
-fixed an incorrect message showing when GhashBone's brain was removed
-doubled the time for the item finding chance on GhashBone's brain (now its about every 18 minutes)
-dog refs will now disappear upon taking their brains, this fixes a glitch (and prevents the possibility of creating a similar glitch) that would have allowed the player to get multiple of the same brain
-now incompatible with the sunny smiles companion mod (read the compatibility section below)
-Rex Brain Swap objectives will reset for cheyenne's brain if the quest has previously been completed
-the Rex Brain Swap quest objectives have been changed to say "(Optional)"


Description:

Now you don't have to just pick one brain and stick with it. And just three brains to choose from isn't enough! You can now try up to six brains! In short, this incredibly immersive mod is sort of an expansion on the quest "Nothin' But a Hound Dog" that allows the player to swap Rex's brain any time they wish. Don't like being defensive with Lupa's brain? Switch to Violetta's for speed! As of now there are also two extra brains with their own effects to choose from, which are Motor-Runner's dogs BoneGnash and GhashBone (their effects are listed below in the "Current Features" section). And with all of the tactical brain changes Rex could possibly take on with this mod, I dare to say that Rex is now your most useful follower!


Why I Created This Mod:

I initially wanted to add more brains to the "Nothin' But a Hound Dog" quest when I figured out that there are more unique dogs like BoneGnash and GhashBone. One day as I was searching the net for a mod that might do this before I created one of my own, I stumbled upon a mod suggestion (link in the credits below) which was for a mod that allowed the player to swap Rex's brains. I decided that this would be a perfect idea, especially if there were more brains. And why if a doctor can swap out a brain once, can they not do it again? Thus, Rex Brain Swap was born!


How It Works:

After the quest "Nothin' But a Hound Dog" is completed, you will be able to then talk to either Doctor Henry, Calamity, or Rex (with 75 Science or 75 Medicine) and choose a special (and also voiced) dialogue option will which open the Rex Brain Swap option menu. From there you can choose another brain to swap with Rex's current brain! It works similarly to the vanilla quest where the screen blacks out and hours pass by (6 to be exact). I've created this mod so that it will work regardless of whether you have completed the quest previously or not! It will re-add brains that should've remained in your inventory had the prior completion of the quest not removed them. It will also add objectives so you can find the brains you've missed! You'll now also have the option of finding and using the brains of BoneGnash, or Ghashbone.


Installation:

If you're downloading by manager everything will go where it needs to go automatically, just make sure you activate this mod in your mod manager. I HIGHLY SUGGEST YOU DOWNLOAD WITH MANAGER. It will place the sound files in their appropriate directory. If you must download manually, place the .esm in the data folder like any other, however, make sure you copy and paste the "Sound" folder and merge it to the one in your New Vegas data folder. 


Requirements:

*These requirements must be met for this mod's features to work, not necessarily for it to RUN as would a DLC requirement
- quest "Nothin' But a Hound Dog" completed (for brain swap menu, extra brains are available during the quest also)
- Rex is your follower and must be alive (which should be obvious)


Current Features:

-a menu feature which can be accessed at any time (and possibly anywhere) to swap brains with Rex
-2 different ways to access the brain swap option menu (doctors in Jacobstown or talking to Rex with skill requirements)
-full voiced dialogue for Doctor Henry, Calamity and Rex
-3 new brains that can be acquired, Motor-Runner's dogs BoneGnash aka Donnie, or GhashBone aka Marie (their names depend on whether or
not you have the "Wild Wasteland" trait), and the brain of Sunny Smile's dog Cheyenne
-a bit of dialogue for sunny smiles regarding Cheyenne's brain
-intricate dialogue/mini quest added to Motor-Runner to get brains from BoneGnash and GhashBone (so you don't have to kill them)
-a separate objective list in the "Rex Brain Swap" quest if you've missed any brains
-renamed brains to "Brain, ..." to sort better in the player's inventory

New Brains:

-BoneGnash's brain gives Rex the "Heavily Medicated" perk, which allows Rex to process chems better, making Stimpaks more
effective (+20 medicine which is equivalent to +12 hp per stimpak).
-GhashBone's brain gives Rex the "Drug Sniffer" perk, every so often for as long as Rex is the player's teammate, he'll acquire a
hidden/buried chem which is added directly to the player's inventory (about 1 every 18 minutes of either Stimpak, Med-X,
Jet, Psycho, or Buffout).
-Cheyenne's brain gives Rex the "Best of Friends" perk, which gives you +2 Charisma, +2 Endurance, and +2 Luck as long as Rex
is your follower. Note that this brain may be difficult to acquire. Cheyenne is young and useful to Sunny Smiles, so she won't
give up Cheyenne willingly. I've tried to make this perk better than the rest so far to compensate for this difficulty. You may
have to kill her, but there is a way around this if you don't want to be mean. Sometimes in the battle between Goodsprings
and the Powder Gangers, Cheyenne will die in the crossfire. This will allow you to easily obtain her brain and early in the game.


Future Versions Will Probably Have:

-brain usage/splicing from creatures besides dogs (most notably deathclaw brains)
-brain case upgrading to make the above feature possible
-re-adding of Rex's old, deteriorating brain (with it's own effect)
-more brains/dog choices 
-brain splicing (combine two brains for more effects)
-brain upgrading/stronger brains
-custom cutscene ending narrated by yours truly
-full integration of the Wild Wasteland perk for Donnie and Marie
-more/better dialogue (creating immersive, voiced dialogue is difficult, but I'm looking into it)



Uninstallation:

In the current version of this mod, there is unfortunately no support for uninstallation. So you can deactivate this mod, but the extra brains will remain in your inventory, so to remove them you will have to figure out their IDs and remove them via script. GhashBone's brain will also become useless if Rex has it in his head after this mod is uninstalled, so make sure IF YOU DO uninstall this mod that you switch his brain to a vanilla brain first . Whatever other changes Rex has received via a brain he had previously will remain if you do not switch to a vanilla brain first.


Compatibility:

Slightly incompatible with Yukichigai's Unofficial Patch. You can put this mod lower in your load order than YUP and it will work perfectly, but YUP tries to make changes to the dialogue which the vanilla quest (and thus my mod) use. It's probably not game breaking, but I'm not sure how it will affect YUP.

Slightly incompatible with the Sunny Smiles Companion mod (one with most downloads and endorsements). This is because the SSC mod does not account for Cheyenne possibly being dead before the player gains sunny as a follower. if the player already has Cheyenne's brain, Cheyenne will
disappear, but the dialogue with Sunny will still be as if Cheyenne weren't dead. In addition to this, if the player is not playing in hardcore mode, and does not yet have Cheyenne's brain, Cheyenne will resurrect if she is dead after some glitching and twitching on the ground for a few minutes. 

There are no other known compatibility issues at this time, but this mod will be incompatible with anything that changes the dialogue for the "Nothin' But a Hound Dog" quest, the script for the quest, or changes the script that's attached to Rex. These were all 100% necessary edits to make this mod flow as wonderfully as it does.


Credits and Thanks To:

-My fiance for some text editing.
-dubbedmk3 for the suggestion/idea, which can be found here forums.nexusmods.com/index.php?/topic/253441-rex-brain-mods/, even though I have never talked to him text or otherwise
-YOU for downloading and endorsing!
-The entire Nexus community for being so awesome! I've found answers to nearly all my problems on the Nexus forums. Cheers guys!