Developmental sequences in the maturation of intrinsic and synapse-driven patterns

Postnatal maturation of cortical circuits is marked by changes in connectivity, subunit composition of synaptic receptors, strength, as well as capacity for plasticity of excitatory and inhibitory synapses. Together, these factors shape the responsiveness of cortical neurons to sensory stimuli and contribute to establishing functional circuits. Experience plays a crucial role in the postnatal process of maturation, especially during windows of heightened plasticity known as sensitive periods. In this chapter, we bring together results from studies that examined the mechanisms underlying postnatal development of excitatory and inhibitory synapses and review them in context of studies investigating sensory circuit function. We report extant literature highlighting common mechanisms of maturation across visual, somatosensory, and auditory cortex, discuss similarities and differences in the time course of maturation and experience-dependent plasticity for all three cortices, and highlight emerging ideas about the contribution of excitation and inhibition in developing cortical circuits.