The biceps have two heads, a short (inner) and long (outer) head. No matter what biceps curl variation you use, the short and long head work together to accomplish the movement. You can't "isolate" one head. But it may be possible to put slightly more focus on one region of your biceps over the other.
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If we look at the anatomy of the biceps, we see that the long head of the bicep crosses the shoulder joint. Because of this, the long head of the bicesp is placed at a more lengthened position when you perform bicep curls while your arms are behind your body. So based on the length-tension relationship, the long head of your bicep needs to work slightly harder during biceps exercises with your arms behind the body, like incline bicep curls.
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On the flip side, when you keep your arms in front of your body (e.g. preacher or spider curls), the short head of your bicep will need to take on more of the work. This is because the long head of your bicep will be more shortened and won't be in a favorable position to maximally contribute to the movement.