Neural Net
From Megaman Mush Wiki
The 'brain' of a Reploid, it can be considered more or less the robot analog of its human counterpart. Neural net damage can be extremely serious and debilitating, and it is commonly held that destroying the neural net of a reploid is the only way to kill one permanently, whether by damaging it beyond repair, depriving it of power, or outright smashing it to pieces.
