Adaptive functions of neurobehavioral plasticity in language learning and processing

Abstract

This article presents a large scope of issues on early and late language plasticity that increase our understanding of the neurobehavioral dynamics of change, the main property of the learning brain. In their pioneering work, Bates and Kuhl have convincingly demonstrated that plasticity is intrinsic to development. Bates has provided new data on the impressive recovery of language in children with focal brain injury, highlighting that both hemispheres support the early phases of this change, contrary to previous assumptions. The fundamental reorganization of the early phonemic system around the age of 8 months proposed by Kuhl, combining neural commitment and social abilities, has powerful cascading effects for subsequent word learning. Our developmental crosslinguistic research on online sentence processing in monolinguals and simultaneous bilinguals has revealed distinctive linguistic patterns of “cue cost”, a multifactorial concept relevant for capturing the microplasticity of the processing system. Whatever the language, the shift around the age of 9 towards the canonical adult pattern indicates an efficient adaptive processing occurring with a small delay in bilinguals. Most salient, from childhood, bilinguals exhibit specific cue cost patterns with interactions. In older French adults, cue cost variability is mediated by processing speed which preserves online syntactic abilities but reveals plasticity limits in Alzheimer’s patients.