Cooperating brain systems in selective perception and action

A neuropsychological hypothesis - the integrated competition hypothesis - is introduced to account for visual attention in the context of distributed brain activity engendered by visual input. Relevant data concern attentional modulation of single-neuron activity in the macaque, extinction phenomena following human and animal brain lesions, and the time course of the attentional state in normal human vision. According to the hypothesis, objects compete for representation in multiple brain systems, sensory and motor, cortical and subcortical. Competition is integrated, however, such that multiple systems converge to work concurrently on the same object. Local priming of target-selective units is used to give a competitive advantage to currently relevant objects. In single cells of monkey cortex, we see direct evidence for both priming and competition. In the human and monkey, multiple brain lesions produce a tendency to extinction, or bias against objects most affected by the lesion. Both spatial and nonspatial forms of extinction are described. In normal behavior, interference between two attended objects lasts for hundreds of milliseconds. These findings suggest that "attention" is a slowly evolving state in which multiple brain systems settle together on the selected object, making its different properties available together for control of behavior.