This INSPIRE award is partially funded by the Perception, Action, and Cognition Program and the Biological Anthropology Program in the Division of Behavioral and Cognitive Sciences in the Directorate for Social, Behavioral, and Economic Sciences, and the Office of Integrative Activities.
Humans naturally learn to speak and use language. It is one of the defining features of our species. Understanding the biology of this extraordinary capacity is relevant to the fields of neuroscience, linguistics, genetics, psychology, and anthropology. Human speech and language involve intertwined processes, including the perception of signals (i.e., sounds, words, manual gestures, signs in sign language), the learning of phased movements of the mouth, tongue, and larynx to produce combinations of sound elements, as well as the higher-level cognitive aspects of word meaning, language structure, and the understanding of the discourse in which communication occurs. As each of these components may have separate neural and genetic bases, a focus on individual aspects of language helps dissect this complex socio-cognitive behavior. Studies of humans with speech and language disorders have provided insight into candidate genes (FOXP2 and KIAA0319) and brain structures implicated in different elements of language function. However, it is not yet understood the degree to which these genetic and neural building blocks of language are present and vary in nonhuman animals. This research project encompasses an innovative and interdisciplinary approach to investigate this question among humans' closest living relatives, the chimpanzees. A better understanding of these complex interactions will further our knowledge of the neurodevelopmental foundation of disorders affecting language in humans, such as autism spectrum disorder, dyslexia, and verbal dyspraxia.
The project includes a multifaceted examination of individual differences in vocal learning, motor control, and sound-symbol learning in relation to genetic variation, neuroanatomical structure, and molecular expression in the brain. Chimpanzees show marked variation in orofacial motor control that allows some individuals, but not others, to flexibly learn novel vocalizations. To understand the neurobiological differences among chimpanzees related to vocal learning ability, this project will use several cutting-edge analytic approaches, combining detailed MRI brain imagery, sophisticated measurements of microanatomical structure and cellular composition (from an existing histological collection), and innovative computer science-based methods. In addition, genomic analyses will include FOXP2, a gene that plays a critical role in establishing the brain circuitry required for the development of language in humans. However, the function of FOXP2 in communication and orofacial motor control is essentially unknown in primates: this project will be the first to characterize variation in FOXP2 across chimpanzees and examine associations with individual differences in brain structure, gene expression, and vocal learning (behavioral tests that involve minimal encouragement of the chimpanzees and reinforcement with food rewards, without involving any anesthesia, pain, or distress). Another important dimension of human language is the ability to understand words and their meaning, in both the auditory and visual domains. In humans, the gene KIAA0319, which is involved in brain development and dyslexia, is thought to play a key role in this sound-symbol learning. This project will examine how variation in KIAA0319 underlies differences in brain organization and sound-symbol learning in chimpanzees (housed at the Yerkes National Primate Center and the MD Anderson Cancer Center). All DNA samples, MRI scans, and brain tissue to be used in the study has previously been acquired. The combination of these multiple techniques will result in unique data sets that will transform our ability to compare brain structures and behavioral abilities relevant to language and brain function in chimpanzees and humans.
