Originally Posted by 0311

Hey dude, I feel your pain. Unfortunately, I've found that you cannot specifically target a portion or area of a muscle, only shift some emphasis on it. Your chest muscle operates as a whole. Running on this train of thought, can you flex your inner chest without flexing your entire pec? The answer is no. ;) Therefore, if you start getting into the mindset of using cables and the like trying to "isolate" your inner chest, you'll never grow.

Fortunately, your chest will grow as a whole as long as you continue to have faith in moving progressively heavier weight with compound lifts (ie. flat/incline/decline/whatever) If you continue to build the thickness of your chest, your deficiencies will iron themselves out.