Visual Processing in Subcortical and Cortical Circuits
Date of Award
Doctor of Philosophy (PhD)
In 1887 in Zaragoza Spain, Santiago Ramon y Cajal peered through a microscope at retinal tissue stained with silver-nitrate and began to make exquisite drawings of neurons. More importantly, he also postulated that neurons are information processing units that make connections and are organized into dynamic networks that serve various functions. Later work would provide support of these ideas by showing that synaptic contacts between neurons are organized into specific patterns forming local neural ensembles. Today, we refer to these specific patterns of nerve cells as microcircuits. Each region of the brain contains microcircuits that are responsible for carrying out information processing specific to that region. Microcircuits for roughly 50 different regions in the brain have been published and amazingly, there are similarities in the organization of these circuits across different brain regions.
In this thesis, we will shed light on the question “are there basic principles that govern the organization of intrinsic circuits of the visual system of vertebrates?”. To this end, we will examine three microcircuits of the visual system of non-mammalian vertebrates with the specific aim of elucidating the relationship between connectivity patterns and microcircuit function. We will start with the well-studied isthmotectal microcircuit of birds and reptiles and address how recurrent and lateral synaptic connections influence network behavior in a computational model. Secondly, we will examine the isthmotectal microcircuit of amphibians to address whether feedback neurons in the system can be distinguished on the basis of their intracellular properties measured in-vitro or their visual response properties measured in-vivo. Lastly, we will examine the cortical microcircuit of the turtle visual cortex and explore the time-course and laminar locations of excitatory synaptic sinks using current source density analysis.
Chair and Committee
Michael Ariel, Bruce Carlson, Anders Carlsson, John Clark, Zohar Nussinov
Caudill, Matthew S., "Visual Processing in Subcortical and Cortical Circuits" (2011). Arts & Sciences Electronic Theses and Dissertations. 289.