Committee:

Bilal Haider, Ph.D. (Advisor) (Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology)

Christopher Rozell, Ph.D. (School of Electrical Engineering, Georgia Institute of Technology)

Stanislav Emilanov, Ph.D.  (School of Electrical Engineering, Georgia Institute of Technology)

CORTEX-WIDE CALCIUM IMAGING OF VISUALLY EVOKED NEURAL POPULATION ACTIVITY IN MOUSE VISUAL CORTEX

The traditional method of electrophysiology provides cellular-level, millisecond timescale measurements of neural activity, but it has limitations in probing neural activity across large spatial scales. Widefield imaging (WFI) of genetically engineered calcium-sensitive fluorescence proteins in neurons enables measurements of neural population activity across large areas (~ 5 x 5 mm) with temporal resolution of tens to hundreds of milliseconds. In this thesis, we adapted an experimental and analytical framework for WFI investigation of visually evoked neural activity across the mouse visual cortex. We first validated identification of the primary visual cortex (V1) and higher visual areas (HVAs) through retinotopic mapping experiments. We then measured stimulus-triggered calcium signals in mice performing a visual detection task. The activity profiles were analyzed as a function of task performance and were also compared to profiles measured in mice passively viewing the same visual stimuli with no task. We performed region of interest (ROI) analysis based on the retinotopically registered images across multiple visual areas.  The calcium signal amplitude was positively correlated with stimulus contrast, and signal amplitudes were enhanced during visual detection compared to passive viewing. Further work such as optimizing system functionality and applying a more efficient decomposition method on the WFI data could reduce variability across different imaging data sets and provide more accurate understanding of network dynamics across visual areas and other cortical regions.