ABSTRACT Manual communication, with its very different motoric and perceptual substrate, offers a fresh and exciting opportunity to investigate the biological foundations of language. In a series of experiments, we explore the nature of American Sign Language (ASL) and its neural substrate. Biological and Linguistic constraints on Structure. We investigate the ways in which requirements of production constrain the 'phonological' structure of language, sorting natural constraints imposed by the visual gestural modality from language-particular characteristics. We also initiate new analyses of ASL verbs, which are the blueprint for and the backbone of the ASL sentence. The research aims toward a comprehensive and systematic account of verb class organization, lexical representation, and morphosyntax in ASL. Neurological Control of Language and Movement. The study of sign language probes the interaction of the brain's control of language and of movement. We combine new techniques of three-dimensional computer-graphic movement analyses with linguistic analyses to illuminate neural mechanisms controlling language and movement from an important new perspective: We contrast brain damaged signers with deficits at different levels of linguistic processing and motor control. Biological and Linguistic Constraints on Perception and Action. Signs in American Sign Language are not static, but rather move in complex, highly patterned dynamic arrays. We quantitatively investigate the ability of signers with motor disorders to analyze various types of visual motion stimuli, ranging from the simplest analysis of velocity, to motion with linguistic content. Moreover, we investigate the processing stages underlying their ability to point to memorized target locations in 3-D space. These data sets will help uncover the perceptual-motor underpinnings of the neural substrate for sign language. The convergence of formal linguistic, objective three- dimensional measurement, and neurological approaches in this project will provide fresh perspectives on issues in brain organization for language that are relevant for all natural languages, both spoken and signed.
