The proposal research is part of a larger research program designed to investigate the respective and conjoint contribution of the cerebral hemispheres to visually guided behavior. The functional organization of the brain is characterized by an asymmetric representation of functions in the two hemispheres such that each hemisphere plays a different role in the realizing of behavior. One part of this project is concerned with specifying the nature and quality of the visual information that each hemisphere can elaborate in early visual processing. This will be examined in unilaterally brain-damaged subjects,starting with a thorough examination of sensory capacities to determine the composition of the representations on which subsequent cognitive operations are performed. Considering that how information is represented greatly influences how it is processed, the nature of the operations underlying face perception will be determined by examining the characteristics of the relevant information that need to be extracted for efficient processing and by modifying task demands to uncover the processing efficiency of the hemispheres as a function of the quality of the information and of the requirements of the tasks. A second part of this project will pursue the investigation of interhemispheric communication and of the role of subcortical structures in the coordination of hemispheric activity by examining the capacity of commissurotomized patients to perform tasks that require exchange of information across the disconnected hemispheres. The experiments will seek to determine the nature, extent, and limit of the functional capacities of subcortical structures in hemispheric integration and will reexamine some of the characteristics of the disconnection syndrome by manipulating the informational contents that have to be communicated between the disconnected hemispheres. The two parts of this research program toward a better specification of the conditions for an integrated functioning of the brain and will provide information concerning the mechanisms by which the two hemispheres complement each other, and cooperate with one another, in the production of unified and purposeful behavior.