The cognitive system is organized hierarchically. The most basic perceptual systems are located at the bottom of the hierarchy, and the most complex cogntive (e.g. memory, problem solving) systems are located at the top of the hierarchy.
Information can flow both from the bottom of the system to the top of the system and from the top of the system to the bottom of the system. When information flows from the bottom of the sytstem to the top of the system this is called "bottom-up" processing. Lower level systems categorize and describe incoming perceptual information and pass this descriptive information onto hiher levels for more complex processing.
Contributed by Jeff Stepnisky, November 30, 1995 Dictionary Home Page