Undergraduate Honors Theses

Thesis Defended

Spring 2017

Document Type

Thesis

Type of Thesis

Departmental Honors

Department

Psychology & Neuroscience

First Advisor

Michael P. Saddoris

Second Advisor

Heidi E. W. Day

Third Advisor

Carol E. Cleland

Abstract

Electrophysiology is an important technique using chronically-implanted electrode arrays, which allow for recording of neural activity in vivo during behavioral tasks that require cue and reward associations. Recordings are used to study how patterns of neural activity encode behaviorally-relevant information and how the disruption of this encoding can occur following cocaine experience. Behavioral testing and acute manipulations (such as chemogenetics) of associative behaviors can take place over several days. To precisely assess the progress of neural encoding over time, it is important to identify single unit neurons across multiple recording sessions. Here, we examined neurons in the nucleus accumbens (NAc) shell of Sprague-Dawley rats during a Pavlovian first-order conditioning task. To establish whether neurons are identifiable across multiple sessions, cells were identified using multiple metrics. These included principal component analysis, waveform voltage patterns, inter-spike interval patterns, and autocorrelation. We demonstrate that cells show specific, regular features across each metric and could therefore be identified across multiple sessions. Next, we analyzed the associative learning-related encoding of an individual neuron under two conditions: CNO-induced inhibition of hM4Di-expressing DREADDs in the shell on one day, and a control saline injection on the other. To demonstrate the efficacy of this approach, we us as an example a single unit that was determined to be the same across CNO and saline conditions by waveform and autocorrelogram analysis. We found that this cell exhibited differential firing patterns under each condition, indicating variable selectivity of cue encoding and motivated approaches to cues and foodcups.

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