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theses

Approach-avoidance conflict occurs when balancing actions intended to obtain a positive outcome against the known and unknown risks of a negative outcome. Here, we use the PORT, developed by Dent et al., (2014), to evoke a natural approach-avoidance conflict by exploiting predator-prey relationships. Briefly, to obtain a reward, animals must traverse through a chamber containing the innately feared odor, 2-Phenylethylamine (PEA), a synthetic volatile component of cat predator urine. Thus, this task nicely mimics the real-life tension between foraging and predation risk and should recruit natural circuits involved in processing innate threats. Both females and males demonstrate an initial apprehension to enter a chamber scented with predator odor, but not one scented with a novel odorant (MV) or clean bedding (CB). This apprehension was followed by increased time spent within those chambers, indicating similar exploratory behaviors to both a novel and predator odor. This is in direct opposition to previous literature demonstrating avoidance to predator odors. Females and males exposed to MV, exhibited similar levels of cFos immunoreactivity within the piriform cortex and when collapsing across all 13 brain regions quantified in this study. However, females had reduced cFos activity within the dorsomedial (DM) hypothalamus compared to males. Unlike MV and CB, behavioral responses between females and males diverged with exposure to PEA. In the presence of the predator cue, all females quickly transited the box to obtain the reward, while males exhibited a highly variable, possibly bi-modal distribution where half the males transited quickly but about half took longer than any female. This differential behavioral response was reflected by a PEA induced enhancement of female cFos immunoreactivity within the piriform cortex, DM hypothalamus, and when collapsing across all brain regions. Interestingly, it was only during PEA exposure, where this behavioral divergence occurred, that females showed greater DM hypothalamic activity than males. In both sexes, PEA exposure evoked heightened cFos activity within the central amygdala which indicates the anxiogenic nature of this stimulus. We also find that regardless of odor condition, females exhibited greater basolateral amygdala activity than males, whereas males demonstrated heightened defensive behaviors such as immobility and time spent close to the chamber walls. Overall, the findings suggest that the behavioral and neural differences between males and females in response to predator threat may reflect sex differences in risk-reward decision-making.

ETD_10187

M.S.

Includes bibliographical references

doi:10.7282/t3-wt0n-kw17

ETD graduate

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