One of the hallmarks of the young brain is it ability to be sculpted by experience especially during critical periods in development. However, the mechanisms underlying this early learning process and how they relate to learning processes in adult are unknown.

The young brain is structurally different from the adult brain and contains additional circuits that are formed by subplate neurons (SPNs). These neurons reside in the white matter and most of them disappear during development. After the critical period ends – when SPNs are no longer present - only limited plasticity is present. Thus SPNs might participate in types of synaptic plasticity that occur only during the critical period.

We describe functionally the changing circuits present in the developing neocortex. In particular we describe the circuits SPNs are associated with, how these circuits are engaged by sensory activity, and how these neurons can provide a template for the future cortical organization. We then show how the presence of SPN circuits can aid neocortical development. We then show how disruption of these circuits in early development can lead to altered cortical function and cause symptoms of neurological disorders.