Norepinephrine and second messenger encoding of temporal threat proximity

PROJECT SUMMARY Individuals must predict threats in the environment in order to survive. However, maladaptive threat computation processes can lead to psychiatric disorders such as post-traumatic stress disorder. For threat predictions to be adaptive, they must be temporally accurate and capable of predicting threats which may be

distant in time. However, the mechanisms underlying predictions involving temporal distance are poorly understood. The overall aim of this project is to determine the neural substrates underlying learned encoding of temporal threat proximity and temporally accurate defensive responses to threat. I have recently shown that the in the prefrontal cortex, norepinephrine represents a teaching signal

which also encodes proximity of incoming threat. Furthermore, threat-predictive stimuli evoke increases in prefrontal cyclic AMP (cAMP) concentration that persist past the stimulus and to an aversive event, consistent with temporal linkage of predictive stimulus to outcome. These results are consistent with both the encoding of

temporal information within prefrontal cortex (PFC) and the necessity of PFC for delayed threat prediction. Taken together, current work on the prediction of distant threat suggests an interplay between norepinephrine signaling of threat proximity during learning, second messenger linkage of predictive cue to distant

outcome across learning, and encoding of threat proximity in PFC in order to effect accurate defensive behavior. The proposed project seeks to test this model of threat prediction. The proposed project seeks to understand the roles of norepinephrine, second messengers, and prefrontal neurons in encoding of and effecting behavioral responses to threat proximity. In Aim 1, I will

determine the role of norepinephrine time-to-danger signals in supporting temporally accurate threat responding and encoding of threat proximity information by prefrontal cortex. I will do so by employing behavioral optogenetics and in vivo calcium imaging, techniques essential to this work and my future systems

neuroscience studies. In Aim 2, I will determine whether cAMP links temporally distant events during learning by determining whether sustained cAMP supports delayed threat preparation and elucidating the effect of temporal distance on threat cAMP. I will use optogenetic manipulation and fluorometry of prefrontal

cAMP to complete these aims, as well as to gain personal expertise in future manipulation and measurement of second messengers, which are key to learned behavior but highly understudied in vivo. In total, I seek to understand the neural processes underlying the accurate prediction of threats across timescales.

The proposed project will accomplish the technical training goals aforementioned, and I will also use this fellowship for my personal advancement in science communication, teaching, and mentorship within an environment of technical experts. My sponsors, collaborators, contributors, and research environment are

technically and intellectually equipped to support the proposed training and research under this fellowship.