transmit the sensory impulse to the appropriate part of the brain or spinal cord for interpretation and processing; also known as association neurons.
depth. 1  the distance from the top downward, from the surface inward, or from front to back. 2  perspective, as in a painting. 3  the quality or condition of being deep; deepness; specif., 4  intensity, as of colors, silence, or emotion.
Hints: It is useful to use a concept of depth in an expression. I have labeled the spaces in the expression below by their depth. The depth of a space is the number of inward crossings needed to reach it. There must be rectangles enclosing spaces of maximal depth in the expression.