The two-part paper examines the neurobiological processes of synapse overproduction, synapse elimination, and issues of language acquisition and attrition. The first part consists of diagrams and notes explaining some basic terms and concepts of neurobiology: cortex; white matter; neuron; synapse; synaptogenesis; and development and organization of neuronal connections. The second part details, in narrative, two processes correlated with maturation (synaptic elimination and stabilization of the synapses that survive the elimination stage) and their implications for second language learning and first language attrition. These processes are then applied to hypothetical cases of children emigrating from their first-language environments before the age of 8 and after the age of 12 to explain patterns of language acquisition, maintenance, and loss. (MSE)