THEME I

BIOLOGICAL FACTORS UNDERLYING THE DEVELOPMENT OF LANGUAGE AND LITERACY SKILLS.

Theme Leader: R. Harrison, The Hospital for Sick Children, Toronto

In an hierarchical model, language and literacy evolve as complex behaviours based on more fundamental building blocks. At a basic level, adequate sensory input from auditory and visual systems is essential. Transmission pathways from periphery to cortex must develop such that there are adequate central representations of speech signals, and their abstracted visual equivalents. Neural information pathways between auditory and visual areas, together with motor cortex have to be established adequately.

What is meant by each of the terms "adequate" is very poorly understood. Full language and reading ability requires that each stage of the process be completed more or less normally. This developmental continuum can be perturbed at any point in time, and the hierarchy can be damaged at any level. However, early deficits are more likely to affect more basic components of the hierarchy (although not always).

The goal of Theme I is to understand more fully the basic developmental neural processes that provide the substrate for all the higher level mechanisms that culminate in language and literacy behaviour.