Award Date


Degree Type


Degree Name

Doctor of Philosophy in Biological Sciences


Life Sciences

First Committee Member

J. Steven de Belle, Chair

Second Committee Member

Andrew Andres

Third Committee Member

Jeffery Shen

Fourth Committee Member

David Arnosti

Graduate Faculty Representative

Jefferson Kinney

Number of Pages



Animals possess the ability to associate neutral stimuli in their environment with both rewards and punishment. A conditioned stimulus (CS1) such as a smell or sound, can become associated with an unconditioned stimulus (US), such as a food reward, to elicit what is known as the conditioned response (CR). This type of learning is commonly referred to as classical conditioning or first-order conditioning (FOC). Second-order conditioning (SOC) is an extension of this type of association wherein a novel stimulus is introduced (CS2) and associated with a previously conditioning first-order stimulus (CS1). As a result, the organism may show an attraction or avoidance towards the novel stimulus (CS2) even though it was never directly paired with the original unconditioned stimulus (US). In nature, there is a potential for SOC in almost any circumstance involving exposure to a sequence of learned events. For example, honeybees often memorize complex navigational pathways by associating landmarks with the presence of flowers. While a house or a tree may not reward the insect with nectar, it can be associated with a series of stimuli that eventually lead to a beneficial reward.

My work in this dissertation focuses on conclusively demonstrating SOC for the first time in Drosophila along with utilizing genetic and molecular techniques to in- vestigate the neuronal basis of this behavior. The fruit fly has numerous advantages underlying its usefulness as a model organism: its genome has been sequenced, it possesses a relatively short time of development, it can be easily subjected to genetic alterations, and it is studied by numerous laboratories around the world. Using an au- tomated, computer-controlled olfactory-based learning paradigm, I will demonstrate the ability of Drosophila to form these complex, higher-order memories initially be- lieved to be reserved only for the vertebrate learning model. In addition, I will show that Drosophila are also capable of conditioning in situations of complex odor presen- tations for both first- and second-order conditioning. Furthermore, through the use of a transgenic neuron silencing approach exclusive to the Drosophila animal model, I will examine whether previously studied neuronal circuits fulfill similar roles in both first- and second-order conditioning.


Classical conditioning; Conditioned response; Conditioning; Drosophila; Fruit flies; Pavlov; Second-order conditioning


Animal Sciences | Biology | Neuroscience and Neurobiology

File Format


Degree Grantor

University of Nevada, Las Vegas




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