Elaida Dimwamwa
BME PhD Defense Presentation

Date: 2024-05-02
Time: 10:30
Location / Meeting Link: Kendeda 230; https://gatech.zoom.us/j/5566530165?omn=97077320181

Committee Members:
Garrett Stanley; Adriana Galvan; Bilal Haider; Dieter Jaeger; Annabelle Singer


Title: Towards demystifying the “mysterious creatures of the deep”: corticothalamic feedback in sensory processing

Abstract:
With a mere double-tap to our pocket, for example, we can immediately assess whether the sensation in our fingers matches our expectations and determine whether our cloth mask is missing amid a wallet and keys. Remarkably and effortlessly, we identify and discriminate between objects on a daily basis. While the neuronal processes underlying our ability to complete such sensory-based tasks are canonically studied as feedforward neuronal pathways, numerous feedback pathways interact with the feedforward pathways to enable us to perceive the world through our senses. Corticothalamic feedback from layer 6 of the cortex (L6CT) is one such process that provides copious inputs back to the thalamus, but its function remains elusive. 40-60% of first-order thalamic inputs derive from L6CT neurons, thus positioning L6CT neurons to play an essential role in thalamocortical sensory signaling for sensory perception, which we elucidate through two studies. Using the somatosensory whisker system of awake, transgenic mice selectively expressing channelrhodopsin-2 in L6CT neurons, we investigate how L6CT neurons modulate thalamic and cortical activity and reveal that L6CT neurons can both enhance and suppress thalamocortical excitability in a manner that is dependent on both the firing rate and synchrony of the L6CT inputs (Chapter 2). We then determine the precise activity patterns of L6CT neurons in mice behaving in a somatosensory detection task and reveal that not only are L6CT neurons sensory responsive in the awake and behaving animal, but that their activity encodes the choice of the animal, both in their sensory response as well as the pre-stimulus synchrony (Chapter 3). Taken together, this thesis provides evidence for L6CT neurons as dynamic regulators of thalamocortical excitability that contribute to performance in sensory detection.