This comes up daily for me...
I notice how a sense of a separate I is placed on sensations in the center of the lower head and upper neck area, serving almost as an anchor for this sense of separate I.
The experience of the rest of the body is of space, with just a few sensations here and there appearing in space, but these particular sensations appear as more dense, more substantial, as a tension, a contraction. It is almost as if there is a tensing there to allow for a better anchor for the sense of I.
And when this sense of a separate I is anchored there, the sense of (separate) Other is placed at other locations in space... on certain sensations, thoughts, images, people, situations, land/cityscapes and so on.
It is very curious, and almost comical when it is noticed.
There is a contraction in some muscles in the upper neck/lower head area, making this area appear more dense than the rest of the body (which is just space). And these serve as an anchor for a sense of a separate I, allowing other things in the field to appear as Other.
And when this is noticed, and allowed fully, it all softens. The sensations become more transparent and as space. The sense of a separate I is not anchored anywhere in space and is relaxed, or falls away. And with it falls away the sense of a separate Other as well. Now, the field as it is, without any separate I or Other, arises more as it is. As a field without the sense of a center of a separate I (placed on sensations, tensions, somewhere in this physical body.)