Psychology Ph.D. Dissertations

Title

The Homing Pigeon Hippocampus and the Spatial or Feature Encoding of Reward Probability and Risk

Date of Award

2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Psychology/Experimental

First Advisor

Verner Bingman (Advisor)

Second Advisor

HeeSoon Lee (Other)

Third Advisor

Richard Anderson (Committee Member)

Fourth Advisor

Howard Casey Cromwell (Committee Member)

Fifth Advisor

Sherona Garrett-Ruffin (Committee Member)

Abstract

The current study examined reward probability associative learning to either spatial or feature information in homing pigeons in an open-field, laboratory setting. Additionally, the role of the avian hippocampal formation (HF) was examined in the current study by using both control sham-lesioned and hippocampal-lesioned animals in spatial or feature contexts in which rewarded goals varied in differential risk-reward properties. Homing pigeons were divided into two main experimental conditions, space or feature, and were then divided again into two brain manipulation groups, control sham-lesioned or hippocampal-lesioned. Animals were trained to locate three specific risk-reward (High-Variable 75%, Low-Variable 25%, and Constant 100%) dependent food sites (based on locations or colors) in an open-field environment. It was hypothesized that control sham-lesioned homing pigeons would develop a stronger risk-reward association with spatial information than with feature information. Additionally, it was hypothesized that control sham-lesioned and hippocampal-lesioned homing pigeons trained to feature information would perform similarly on a risk-reward based discrimination. Furthermore, it was hypothesized that control sham-lesioned homing pigeons trained to spatial information would perform differently from hippocampal-lesioned homing pigeons on a risk-reward discrimination based on space. Results indicated that homing pigeons that were provided with feature information were more likely to choose the riskier outcome during High-Variable trials, the constant outcome during Low-Variable trials, and made fewer incorrect choices in comparison to homing pigeons that were only provided spatial information. Control sham-lesioned and hippocampal-lesioned homing pigeons trained to feature both learned to seek out risk-reward outcomes and there were no significant differences in performance. By contrast, performances of control sham-lesioned and hippocampal-lesioned homing pigeons trained to space were significantly different. Hippocampal-lesioned space birds made many more first choices to incorrect bowls and were less likely to choose both variable bowls in comparison to control sham-lesioned space homing pigeons, suggesting a development of risk-aversion.

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