p143fig04.21 Oriented simple cells can respond at the ends of thick enough bar ends, but not at the ends of thin enough lines.  See the text for an explanation of why this is true, and its implications for visual system design.<BR>|| Hierarchical resolution of uncertainty. For a given field size. Different responses occur at bar ends and line ends.  For a thin line no detector perpendicular to line end can respond enough to close the boundary there.  Network activity.