Neural Mechanisms of Attention

Abstract

The brain is capable of carrying out multiple information processes simultaneously, but the capacity of our consciousness is limited and therefore must concentrate on part of the information process. This selection mechanism is called attention. How attention is allocated determines the efficiency of our mental processes; it is probably a central issue of the brain function. Specifically, our action is controlled in parallel by both conscious and unconscious processes. Unconscious processes include many kinds of reflexes and learned actions. Learned actions are particularly interesting because they initially (be fore practice) require consciousness and attention but become automatic after repeated practice (characterized as procedural learning). Therefore, we eventually acquire a large repertoire of learned actions that can be performed automatically and simultaneously. This allows us to perform a complex action, such as keyboard typing, because elementary movements that constitute the complex action can be performed automatically.
We examined spatial attention using a new visual illusion of motion called “line motion effect”. A line, which is presented physically at once, is perceived to be drawn from one side when attention is captured to that side of the line by a preceding visual cue stimulus. This effect is due to acceleration of visual information processing at the locus of attention. The motion illusion is produced by both stimulus-induced (bottom-up) and voluntary (top-down) attention, suggesting that the two kinds of attention act on relatively early stages of visual processing. Using the induction of illusory line motion as a measure we identified how various modes of spatial attention may be represented and reorganized in the brain. Based on these findings, we proposed a model that allows multiple functional modules in the brain to operate simultaneously but as an integrated system.