The long-term goal of this research program is to develop a full explanation of the vocabulary problems associated with developmental language impairment (LI). The current objective is to examine three memory processes that support word learning: encoding, consolidation, and retrieval. Encoding, the experience-dependent process via which a new memory is formed, is followed by consolidation, the slower experience-independent process via which the fragile new memory is stabilized, enhanced and integrated into a network of related memories. Subsequent retrieval of the newly learned information can further strengthen the memory trace and can set in motion the processes of re-encoding and re-consolidation. The central hypothesis is that the word learning problems that characterize LI are a consequence of deficits in experience-dependent memory processes. Experience-independent processes are not affected. This deficit alone is enough to impair word learning over shorter and longer retention intervals and to result, ultimately, in a small and shallow vocabulary.
The specific aims are to 1) determine the integrity of experience-dependent and -independent memory processes of learners with LI;2) identify experiences that promote optimal encoding among learners with LI;and 3) describe the complex interactions between (re)encoding, (re)consolidation, and retention interval that culminate in poorer or stronger retention among learners with LI. The research strategy involves a series of six training experiments wherein the memorial processes that support word learning and retention are detailed across the course of a single week. Manipulation of the number and type of training exposures allows determination of optimal encoding experiences. All experiments will involve comparisons of college students with LI to college students who are unaffected. Three different schedules of testing allow measurement of encoding, all three stages of consolidation, and re-encoding/reconsolidation.
The project will yield new insights about the word learning challenges associated with developmental language impairment (LI), a condition that affects over 12 million adults in the United States. The focus is college students with LI. New information about the experiences that optimize their learning is critical for these citizens who, having made it to college, have an opportunity to contribute to society but who, without adequate support, are at a high risk of failure.
|McGregor, Karla K (2014) What a difference a day makes: change in memory for newly learned word forms over 24 hours. J Speech Lang Hear Res 57:1842-50|
|McGregor, Karla K; Oleson, Jacob; Bahnsen, Alison et al. (2013) Children with developmental language impairment have vocabulary deficits characterized by limited breadth and depth. Int J Lang Commun Disord 48:307-19|
|McGregor, Karla K; Licandro, Ulla; Arenas, Richard et al. (2013) Why words are hard for adults with developmental language impairments. J Speech Lang Hear Res 56:1845-56|