Sketchpads In and Beyond the Brain

Abstract

A model of human cognition is presented in which peripheral sensory images are selectively enhanced by corticofugal pathways. The same processes also generate quasi-sensory mental images even in the absence of sensory stimulation. This inversion of forward sensory processing can come about through hillclimbing algorithms or a type of Hebbian synaptic facilitation I call inverse learning. The neural mechanisms that enable us to simulate actions and evaluate alternative scenarios, are described as internal sketchpads. It is further argued that early artistic expression and language origin can be understood as natural extensions of cognitive processes in which central symbolic neural activity is projected outward to generate images and symbols.