From a neurobiological perspective, the present paper addresses (1) the input-intake distinction commonly made in applied linguistics, and (2) the role of selective attention in transforming input to intake. Primary emphasis is placed on a neural structure (the nucleus reticularis thalami) that appears to be essential for selective attention. The location, connections, structure, and physiology of the nucleus reticularis thalami are examined to illustrate its critical role in information processing. By orchestrating the selection and enhancement of relevant sensory input, the nucleus reticularis thalami acts as a "conductor" of neural systems involved in learning. It is argued that investigations of brain structures such as the nucleus reticularis thalami provide a more fundamental understanding of language acquisition mechanisms.