Visual-spatial working memory, attention, and scene representation: a neuro-cognitive theory

This paper addresses the issue of how visual-spatial working memory, attention, and scene representation are related. The first section introduces a modified two-stage conception of visual-spatial processing. "Stage one" refers to low-level visual-spatial processing and computes in parallel for the currently available retinal information "object candidates," here called "visual-spatial units." An attentional process called "unit selection" allows access to stage two for one of these units at a time. Stage two contains high-level visual-spatial information that can be used for goal-directions (e.g., verbal report, grasping). It consists of three parallel processing streams. First, the currently selected unit is recognized; second, a spatial-motor program for the selected unit is computed; and third, an "object file" is set up for the selected unit. An object file contains temporary episodic representations of detailed high-level visual-spatial attributes of an "object" plus an "index." An index acts as a pointer and is bound via temporary connections to the attributes of the file. Section two of this paper specifies one part of stage two in more detail, namely visual-spatial working memory (VSWM). It can contain up to four object files. A first central claim is that during sensory-based processing for working memory ("access"), one object file is always "on-line," and up to three other object files are "off-line". A second central claim is that the process of setting up an object file depends on the number and the activation level of already stored files. Based on the concept of activation-based competition between object files, it is postulated that the more files that are stored and the higher their activation is, the longer it takes for a newly set up object file to reach a sufficient level of activation. Activation-based competition is also used to explain "short-term forgetting" by "interference." A third central claim about VSWM is that a "refreshment" process exists that increases the activation level of an index of an object file in order to prevent forgetting or in order to bring the file back to the state of controlling the current action. Finally, section three gives a selective look at a number of experimental data such as the attentional blink, backward masking, dwell time effects, transsaccadic memory, and change blindness. New explanations are offered and new predictions made.