# Acute vs Chronic Stress-Enhanced Fear Learning

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA LOS ANGELES · 2020 · $380,010

## Abstract

Project Abstract
Stress can have a profound detrimental impact on our behavior, predisposing us to anxiety disorders such as
post-traumatic stress disorder and major depression. Given the high prevalence of these disorders
understanding the basic biological and psychological processes is vitally important if we wish to address these
significant problems and develop effective treatments. One question in the literature is whether a single
(acute) exposure to stress or repeated (chronic) stress has similar effects. A second question is how severe
must stress be in order to produce detrimental effects. Do repeated mild stressful experiences have an added
impact that equals that of a more severe acute stressor? Does chronic stress exposure have a greater impact
than an equally intense acute stressful experience? Surprisingly, while there is a large basic science literature
on stress, that literature simply does not answer these questions. This is because the methods employed have
totally confounded the chronic nature of stress with its severity. Typically what is compared are a series of
repeated stressors to a single instance of the same stress. But repeated instances mean that the stress is not
only chronic it is also, in total, more severe. We have developed a method were we can independently
manipulate the chronicity and severity of stress that will for the first time allow us to accurately answer these
important questions. The work begins from our extensive use of an intense acute stressor and the database
we have collected on its effects on physiology and behavior. The design of our acute stressor allows us to
break it into 15 “bits” than can be administered at one bit a day for 15 days because the acute stress repeats
the same aversive stimulus 15 times over 90 min. We can also systematically vary the intensity of our aversive
experience. Our preliminary data already indicate that chronic and acute stress provokes different behavioral
responses. Our first aim tests the hypothesis that the differences occur because acute stress taps into a set of
automatic “nonassociative” processes while chronic stress taps into learning or associative conditioning
processes. Our second aim focuses on the physiological and neural changes that are differentially provoked
by chronic vs acute stressors. Additionally, we will determine to what extent stress severity and not chronicity
is the culprit. The third aim focuses on manipulations designed to block the effects of stress to help elucidate
how stress chronicity and severity produce their effects via different biological mechanisms. We also
hypothesize that males and females have different thresholds for how severe a stressor must be to provoke
maladaptive changes in behavior. That hypothesis if true can begin to help explain why anxiety disorders and
depression are more prevalent in females.

## Key facts

- **NIH application ID:** 9873070
- **Project number:** 5R01MH115678-03
- **Recipient organization:** UNIVERSITY OF CALIFORNIA LOS ANGELES
- **Principal Investigator:** Michael S Fanselow
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $380,010
- **Award type:** 5
- **Project period:** 2018-05-17 → 2023-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9873070

## Citation

> US National Institutes of Health, RePORTER application 9873070, Acute vs Chronic Stress-Enhanced Fear Learning (5R01MH115678-03). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/9873070. Licensed CC0.

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