Although the human brain is an incredibly powerful computational device, it does not have sufficient capacity to process the thousands of sights, sounds, memories, thoughts, and emotions that may arise at any given moment. Mechanisms of selective attention are therefore used to focus the brain's processing resources onto a subset of the many possible sources of information. Previously, attention has been considered to be a unitary cognitive process, but recent evidence has suggested that separable attention mechanisms operate at different stages of processing. The goal of the present project is to isolate and characterize these multiple attention mechanisms, focusing on the stages of visual perception, short-term memory, and response selection. Because these separate attention mechanisms may concurrently influence overt behavior, it is difficult to isolate them by means of traditional behavioral measures of performance. We will therefore use electrophysiological recordings of the brain's activity (colloquially known as `brain waves` and technically as `event-related potentials`) to measure the influence of selective attention at different stages of processing. Although selective processing may be necessary at different stages of processing and may require different neural mechanisms, the brain must also maintain unity of behavioral output, and we will therefore also study how the different attention mechanisms are linked together into a coherent system. This research will help us to understand how the brain copes with an overload of input sources, which will have important implications for the design of future computing devices, and for remediating disorders of cognition.
