A Multidisciplinary Investigation of the Neurocognition of First and Second Language

Increasing evidence suggests that language crucially depends on two long-term memory systems in the brain, declarative memory and procedural memory. Because the behavioral, anatomical, physiological, molecular and genetic correlates of these two systems are quite well-studied in animals and humans, they lead to specific predictions about language that would not likely be made in the more circumscribed study of language alone. This approach is thus very powerful in being able to generate a wide range of new predictions for language. I will first give some background on the two memory systems, and then discuss the manner in which language is predicted to depend on them. One of the key concepts is that to some extent the two systems can subserve the same functions (e.g., for navigation, grammar, etc.), and thus they play at least partly redundant roles for these functions. This has a variety of important consequences for normal and disordered language and other cognitive domains. I will then present evidence that basic aspects of language do indeed depend on the two memory systems, though in different ways across different unimpaired and impaired populations. I will discuss normal first and second language, individual and group differences (e.g., sex differences), and our work on disorders, focusing on developmental disorders (e.g., Specific Language Impairment, dyslexia, autism, and Tourette syndrome).