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.
Shallow means not very deep. Used metaphorically it is a derogative term used to describe people who are perceived to be superficial or without depth. There is no standard definition of what constitutes depth in this sense, but usually an individual is considered deep if they seem to be philosophical. By contrast, somebody who appears superficial, materialistic, or petty is likely to be denounced as shallow.