Thesis: Ph. D., Massachusetts Institute of Technology, Department of Brain and Cognitive Sciences, 2014.Cataloged from PDF version of thesis.Includes bibliographical references.In the core of this thesis I test and confirm the hypothesis that separate classes of interneurons respond differentially to sensory stimulation independent of volitional or other top-down control on the part of the animal. I also test and confirm the hypothesis that, based only on bottom-up sensory stimulation the activity of two major classes of interneurons (adapting Parvalbumin positive and facilitating Somatostatin positive interneurons) predominates during different phases of what corresponds to natural sensing cycles in a behaving rodent. These questions are addressed using an in vivo mouse model with intrinsically fluorescent, but differentiable, interneuron populations combined with 2-photon imaging, Ca²+-sensitive dyes. Anesthesia and electrical control of facial muscles allowed for naturalistic stimulation without the confounds presented by volitional whisking and unknown top-down or behavioral states. Additional chapters in this thesis focus on ancillary work related to computational modeling of neural systems and systems' level perspectives on maturation and disease.by Ethan M. Skowronski-Lutz.Ph. D.