Clarissa Whitmire

PhD Thesis Defense

Date: Tuesday, October 24, 2017

Time: 9:00 AM

Location: EBB 1005

Thesis Committee members:

Advisor: Garrett Stanley (Georgia Institute of Technology)

Dieter Jaeger (Emory University)

Robert Liu (Emory University)

Chris Rozell (Georgia Institute of Technology)

Cornelius Schwarz (University of Tübingen)

Title: The role of thalamic state in dynamic tactile encoding

Abstract: Sensory pathways are critical for extracting information about the local environment to guide our actions and behaviors. The internal representation of the outside world is built on patterns of neural activity, commonly referred to as the ‘neural code’. While we often think of the neural code as a linear mapping from stimulus to spikes, it is actually extremely complicated and nonlinear even very early in the sensory pathway. In particular, the neural code explodes in complexity at the thalamocortical circuit where it has been hypothesized that the thalamus gates information flow to the cortex through dynamic transitions in thalamic state. Mechanistically, the baseline membrane potential of an individual thalamic neuron controls its state, or firing mode. Here, we have found that the thalamic state, and presumably the subthreshold membrane potential, can be externally modulated by sensory stimulation, identifying a role for sensory driven state manipulations. Furthermore, we have found that manipulation of thalamic state affects stimulus-evoked cortical dynamics, consistent with the view that the thalamus can gate information flow to cortex. Finally, we investigated the link between thalamic state transitions and the transmission of precise sensory information. Through this work, we provide evidence that the state of the thalamus determines what types of information are transmitted to cortex as well as the dynamics of the evoked response. Dynamic shifts in thalamic state set the stage for an intricate control strategy upon which cortical computation is built.