Fallout: New Vegas implants

Talking to Doctor Usanagi reveals that she sells physical implants to augment your S.P.E.C.I.A.L. abilities, and two special implants, a sub-dermal implant that makes you more resistant to damage and a implant that allows you to regenerate health.

General
You can only apply a limited number of implants, the limit being determined by your starting Endurance PLUS any additional increases to Endurance via Intense Training. The implant for Endurance will NOT allow you to get an extra implant. For example, if your starting endurance = 6, you can get 6 of the 9 possible implants. If you boost endurance to 7 with the implant you still will only be able to get a total of 6 implants. Endurance-increasing items (chems like Buffout or apparel like Wasteland outfit) will NOT be taken in account for implants, either, as they are temporary.

Having an implant installed will affect the perks available to you when you level up, treating the increased stat as a permanent change. In this regard implants behave the same as Intense Training.

Using console commands to increase your endurance will not increase the number of implants available. It appears that the value of your endurance at the start of the game is what is used. (Unconfirmed: see note regarding Intense Training)

Physical Implant
Each SPECIAL stat can be raised only once via Doctor Usangi's implants, and they're 4,000 caps a piece. If your Special is at 3 or below, she will only charge 3,000 caps(it is possible to lower your SPECIAL through certain aid items to only pay 3000 caps for an implant). You cannot raise a natural stat above 10, i.e. if you started with a base Intelligence of 10, you could not raise it to 11. Should a stat be raised to 10 with the Intense Training perk, the game will permit you to buy that implant without benefit:


 * Strength: Hypertrophy Accelerator
 * Perception: Optics Enchancer
 * Endurance: Nociception Regulator
 * Charisma: Empathy Synthesizer
 * Intelligence: Logic Co-Processor.
 * Agility: Reflex Booster
 * Luck: Probability Calculator

Special Implant
Special implants adds special effects.


 * NEMEAN Sub Dermal Armor: adds 4 to your Damage Threshold and the price is 8,000 caps.
 * PHOENIX Monocyte Breeder: adds hitpoint regeneration at a rate similar to that of the Solar Powered Perk (1 HP / 10 sec). The price is 12,000 caps.

Videos
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Bugs

 * Sometimes purchasing the strength implant does not increase strength.
 * Sometimes there is no dialogue option for intelligence implant. If you experience this bug it may be fixed by temporarily lowering intelligence with alcohol.
 * Removing an implant's related perk through the use of console does not refund your total number of implants available. Meaning if you have Endurance 5 and have 5 implants, removing an implant perk will not allow another implant to be installed. Furthermore simply adding an Endurance point from the console does not adjust the "5 of 5" capacity from the example above. The only known solution is to add the Intense Training perk, select endurance (assuming the character does not have 10 endurance already), purchase the "replacement" implant normally, and then remove both the Intense Training perk and the leftover endurance point afterwards.