1. Straight bar pushdowns ( more lateral, but could work long head if lean body forward)
2. Rope pushdowns (lateral, again ditto)
3. Underhand pushdowns (long head)
All different grips puts more stress on different head, note I mentione " more stresss", does not mean other heads don't come into play.
Normal grip ( lateral)
Neutral grip ( Medial)
Reverse grip ( long)
Also, body movement plays a role. eg. leaning forwards.
Hope this helps.
bk