Rogue and Young are right, bro. The pecs are serviced
by the same tendon of insertion. There really IS no
upper, middle, lower, inner, or outer pecs, though you
can hit certain portions a bit harder than others
with certain exercises.
The question is, though, *why* focus on a particular
area when you could do an exercise that hits them ALL
really hard? I've seen people do weighted dips exclusively
and get very good, complete pec development (check
out some of the gymnasts...for their bodyweight, they're
supporting light or middleweight-competitive pecs).
If you want inner pec stimulation, just train hard and
be sure to spend more time with your girlfriend than
you do in the gym or even THINKING about the gym. Whether
or not your inner pecs are really freaky depends on
how lean you are--that is, what you can SEE--and
your genetics. Lt. Heavy Team Universe champion Ron
Coleman had a gigantic cleft between his "inner pecs"
purely by birthright. Others have pecs that touch yet
cannot flat bench the bar and one wheel/side.