Bottom Up (BU) (sensory) and Top Down (TD) (cognitive)
systems analyze the details and use existing knowledge to reconstruct them into a recognizable "whole"-- to produce a behavioral response
systems take in details through the senses and relay them to the brain to form an initial perception
Perception is the ability to make sense of the environment
Attention is the deliberate choice to concentrate on a sensation
When we see a bluebird --
BU systems simultaneously relay multiple details such as color, depth, form and movement to the brain. TD systems put the details together into a mental image.