Language Impairment is one of the most common communication disorders treated by speech-language pathologists. The disorder is characterized by impaired development of spoken language that cannot be attributed to hearing loss, intellectual disabilities, or other known neurological deficits (Benton, 1964). A major challenge in developing effective interventions for DLD is that the impaired learning mechanism underling the disorder is not yet understood. The project?s overarching goal is to fill this critical gap, so that treatment can be delivered in a manner that maximizes learning success. A leading theory suggests that the underlying cause for the language learning difficulties in children with DLD is a deficit in the ability to implicitly extract regularities. Within the framework of this theory, explicit learning strategies should be used to support learning in children with this disorder. Indeed, treatment provided to school-age children with DLD relies heavily on explicit learning by breaking down complex linguistic structures and syntactic regularities into small units that are taught explicitly, using verbalization and memorization. However, these teaching techniques may not be effective as rely on language-based explicit learning that is known to be significantly affected in children with DLD. The proposed project will test a novel hypothesis whereby that the learning deficit in DLD is rooted in an ineffective management of the interaction between explicit and implicit learning, caused by an impaired executive function of shifting. The project proposes that children with DLD demonstrate overreliance on explicit learning, and are failing to initiate a shift to implicit learning during complex learning, because of their impaired executive function of shifting. The project will examine behaviorally and at the neurophysiological level learning of complex structures by children with DLD and by their age and gender matched peers. Learning outcomes, use of strategies, and electrophysiological measured of implicit knowledge will be assessed in relation to the children?s shifting abilities, using two learning paradigms. The two learning paradigms will vary in the extent to which explicit learning is suppressed to evaluate whether eliminating the need to overcome the explicit bias and to initiate a shift improves complex learning in DLD. A well-established electrophysiological measure (the P600 event related potential that detects implicit knowledge of grammatical violations) will determine whether explicit learning hinders the acquisition and/or the expression of implicit knowledge in DLD. Understanding whether learning of complex structures in DLD is facilitated by the suppression of explicit learning strategies and by eliminating the need to shift from explicit to implicit learning will lead to improvement in the teaching techniques employed with children with DLD, and to the development of effective interventions that take into consideration these children?s unique learning profile.
The proposed project is aimed at testing a novel hypothesis that the learning deficit in DLD is rooted in an ineffective management of the interaction between explicit and implicit learning, caused by an impaired executive function of shifting. The project proposes that children with DLD demonstrate overreliance on explicit learning, and are failing to initiate a shift to implicit learning during complex learning, because of their impaired executive function of shifting. Children will perform two artificial grammar learning tasks that require the extraction of regularities from a complex structure. Behavioral and electrophysiological measures of learning outcomes, learning strategies, and implicit knowledge will be assessed in relation to the executive function of shifting, and compared between children with DLD and age and gender matched controls. The two learning tasks will differ in the extent to which the use of explicit learning is suppressed. The suppression of explicit learning will allow the evaluation of implicit learning without the interference of explicit learning, and without reliance on shifting. The study will subsequently determine whether the suppression of explicit learning improves learning of complex structures in children with DLD.
