Mapping cellular and synaptic distributions in the mouse retina
Bleckert, Adam Anthony
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The first step in perception occurs within the circuits of an organism's sensory systems. Throughout many sensory modalities, diverse arrays of neurons are often spatially organized to sample salient features and/or regions within the external environment. Furthermore, within a neuronal circuit, each individual neuron must form correct patterns of connectivity with its synaptic partners to perform the computations necessary to extract and encode these particular features or regions. This thesis attempts to demonstrate how mapping the distributions of the principle output neurons of the retina, the retinal ganglion cells, and their patterns of synaptic connectivity can provide insight to how information within the external environment is sampled and encoded from a synaptic to cellular circuit level within the first stage of the visual system. In Chapter 1, I provide an overview of the importance of understanding cellular and synaptic distributions across neuronal circuits, and how they are established during development. In Chapter 2, I demonstrate that mapping the topographies of functionally and morphologically distinct types of retinal ganglion cells may reveal how visual space is sampled by the mouse retina. In Chapter 3, I utilize a combination of light and electron microscopy to demonstrate that the distributions of inhibitory and excitatory synaptic sites across individual retinal ganglion cells show spatial constraints that may reflect stereotyped patterns of local circuit connectivity. In chapter 4, I assess how inhibitory and excitatory patterns of synaptic connectivity onto individual retinal ganglion cells are established during development by selectively disrupting inhibitory neurotransmission in the retina. In Chapter 5, I summarize the results from each preceding chapter and provide some future directions for questions raised from this work.