Perceptual learning and memory consolidation in adults with and without language impairment

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PROJECT SUMMARY/ABSTRACT The etiology of (Specific) Language Impairment (LI) has been the subject of long debate. Competing accounts include a bottom-up impairment of grammar via impoverished phonological categories (Phonological Deficit Hypothesis), or via broad impairment in procedural or implicit/statistical memory (Procedural Deficit Theory). These accounts need not be mutually exclusive, in that impaired procedural/implicit memory would likely compromise the development of robust phonological representations. Our recent work has found that, following perceptual training on new (nonnative) acoustic-phonetic information, sleep facilitates improved perceptual ability in adults with typical language, but not in adults with a history of LI. How memory consolidation in perceptual learning relates to broader claims about the time course of memory encoding in LI is not yet clear. To this end, we must establish how performance on these tasks relate to relative strengths and weaknesses in procedural and/or declarative memory. Furthermore, we do not know what the neural consequences are of this observed failure in overnight consolidation to the online processing of speech. Therefore, the research outlined in this proposal aims to determine the association between perceptual learning and declarative and procedural memory, and to identify the consequences of failure in offline memory consolidation to the neural processing of speech. These aims will be addressed by combining behavioral data in established procedural and declarative learning tasks with our perceptual learning task. We will also extend our behavioral protocol on perceptual learning to investigate neural processing of speech before and after sleep using functional magnetic resonance imaging (fMRI) techniques. The knowledge to be gained through this research will inform the time course of memory consolidation in individuals with LI, and inform the cognitive substrates of speech sound acquisition in adulthood more broadly. Furthermore, by defining a potentially critical obstacle to successful treatment, this knowledge may contribute to future endeavors to improve remediation outcomes in this common developmental disability. The knowledge to be gained through the proposed project will contribute to four areas of research: (Specific) Language Impairment, speech perception, second language learning, and memory consolidation.