Recent years have seen substantial gains in our understanding of the organization of the cerebral cortex, in parallel with many insights into the nature of perception. This knowledge can now be used to forge a complementary union of neurophysiology and psychophysics, affording unprecedented opportunities to bridge views on perception and its neural counterparts. Cortical processing of visual motion has emerged as a model system for studying the relationship between neural activity and perception. Unlike many other problems in perception and cognition, knowledge of cortical motion processing stages, relevant perceptual phenomena, and computational strategies is now sufficiently well-established to permit facile exploration of their interrelations. One central issue concerns the neural events that underlie perceptual integration of locally derived visual motion signals. This integration process is manifest in our ability to see ordered motion of objects in complex dynamic scenes. The phenomenology of vision affirms that motion signal integration is a robust perceptual phenomenon and a rich, behaviorally significant, context for exploring neural-perceptual dependencies. Proposed psychophysical experiments will test the hypothesis that cues allowing segmentation of visual images into component objects have the capacity to "gate" motion signal integration. These experiments will employ simple two-dimensional moving stimuli that permit adjustment of cues (e.g. transparency, depth, color) to manipulate segmentation into one-dimensional components. Complementary neurophysiological experiments will explore the neural events underlying motion signal integration. Efforts will be made to determine whether responses of cortical motion detectors are modifiable by the same factors known to influence the perceptual phenomenon. This project will focus initially on cortical visual area MT. Emphasis will be placed upon evidence for direct links between neural and perceptual events, through physiological recording in conscious behaving animals. Results should provide insights into how these neural events are dynamically controlled and how they, thereby, mediate perceptual experience. The long-term goal of this project is to contribute to the understanding of biological substrates of perception and cognition. Detailed knowledge of the normal functions of visual cortex shall provide insights into the neural events that underlie dreaming, visual imagery, and manifestations of perceptual disorders, such as hallucinations. Such information will ultimately aid in the treatment and prevention of neurologic and neuropsychiatric disorders of visual perception and visually-guided behavior. These aims are pertinent to the development and use of prosthetic, behavioral, and pharmacological therapies for the visually handicapped.