Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

Andrew Dacks

Committee Co-Chair

Kevin Daly

Committee Member

Kevin Daly

Committee Member

Gary Marsat

Committee Member

Sarah Farris

Committee Member

Sergiy Yakovenko


Neuromodulation is a ubiquitous feature of neural systems, allowing flexible, context specific control over network dynamics by adjusting the biophysical and synaptic properties of neurons. Neuromodulation was first described in invertebrate motor systems and early work established a basic dichotomy for neuromodulation as having either an intrinsic origin (i.e. neurons that participate in network coding) or an extrinsic origin (i.e. neurons from independent networks). Although this dichotomy has been thoroughly considered in motor systems, it has received far less attention in sensory systems. Furthermore, nervous systems are continually subject to a dynamic cocktail of both intrinsic and extrinsic modulators. However, the mechanisms by which single neurons integrate the influence of multiple modulators to alter network function are relatively unexplored. In this dissertation, I discuss the mechanisms by which intrinsic and extrinsic modulators are integrated by single neurons as well as network wide within the context of olfactory processing in the moth Manduca sexta. I begin by discussing the anatomical basis for the integration of two extrinsic modulators, serotonin and dopamine, on principal olfactory neurons. I then discuss the cell-class specific physiological effects of serotonin and dopamine and their distinct effects on olfactory processing. Finally, I discuss the organizing principles and heterogeneity of a diverse group of intrinsic modulatory local interneurons and their potential role in modulating olfactory network dynamics. The heterogeneous nature of neuromodulation is a recurring theme throughout this dissertation as the effects of both intrinsic and extrinsic modulation are generally non-uniform.