The proposed research will test related hypotheses that thalamus plays a heretofore neglected and critical role in cortical processing. In particular, many thalamic nuclei, that together comprise the majority of thalamic volume and that were previously mysterious in function, we now suggest are critically involved in information flow and functional, dynamic binding between cortical areas via cortico-thalamo-cortical pathways. We propose to study these pathways using the mouse somatosensory system as the model involving both in vitro slice preparations and an in vivo behaving preparation. It appears that, in many and perhaps all cases, cortical areas are connected by both direct and these transthalamic pathways. The transthalamic pathways are only recently appreciated, and we aim to explore some basic roles such pathways play in cortical processing. To begin understanding the role of such pathways, we propose to probe basic circuit properties of these pathways to better understand the role of the transthalamic pathways in higher cognitive functioning.