| Description |
A central goal in neuroscience is to understand how neural circuits generate the computations that underlie neuronal responses, sensory perception, and behavior. This requires manipulating their activity and determining the results of these manipulations. Optogenetics is a versatile laboratory technique that uses light to manipulate the activity of genetically modified neurons to express exogenous light-sensitive opsin proteins. Optogenetics allows control of neurons on a millisecond time scale and targets specific types of neurons. An optrode, or optical electrode, is a device capable of delivering light to the deep layers of the cerebral cortex that cannot be reached by surface illumination alone. The Utah Optrode Array (UOA) is a waveguide array intended to conduct light to deep cortical layers over a large volume of cortical tissue. Developed by the Blair/Angelucci team at the University of Utah, the UOA is a 4 x 4 mm square array, with one hundred, spike-shaped, glass shanks that pierce below the cortical surface. Here, we have tested UOAs in non-human primate (NHP) cortex to determine the efficiency of the UOA in delivering optical signals to deep tissue, and the spatial distribution of the neural excitation obtained via optical stimulation through the array. To this purpose, we have used C-fos expression. C-fos is a marker protein that provides an indirect measure of the spatial pattern of neural activation in the brain after immunohistochemical processing. This thesis presents the c-fos related portion of a larger paper incorporating electrophysiological testing data [1]. Our aim in this thesis was to use this protein marker to determine the excitation of neurons induced after using the UOA in macaque monkeys. We found broad-ranging c-fos expression across the visual cortex after UOA stimulation. A Glutamate Block, which prevents synaptic transmission, reduced c-fos expression to the neurons directly underneath the UOA. Our results indicate the UOA is an effective tool for optogenetically stimulating a large area of neurons across all cortical layers. |
