Most of us have experienced an emotionally intense moment etched in our memory. The time when you dropped your ice cream at the age of five and the world felt like it was going to end, or the time you got your heart broken and it still feels so easy to relive. When other memories from the past get blurred, these memories remain vivid.
During emotionally charged or threatening situations like these, cortisol is released to help mobilize energy and attention. Yet its effects on memory are paradoxical: stress can sometimes enhance memory and sometimes impair it, depending on context (Joëls et al., 2011).
Cortisol, Emotion, And Memory: What We Already Know
Emotional arousal plays a powerful role in shaping what we remember (McGaugh, 2004). A key biological player in this process is cortisol, the body’s primary stress hormone. Previous research has shown that emotional arousal can strengthen memory consolidation, particularly when stress hormones interact with the amygdala and hippocampus (McGaugh, 2004). Cortisol influences attention, perception, and encoding, which can indirectly shape what gets remembered (Joëls et al., 2011).
However, much of this work has focused on individual brain regions, treating memory as the product of localized activity. This approach overlooks a critical fact: memory depends on interactions between brain systems, not isolated areas.
A Dynamic Approach To Stress And Memory
To address this gap, Huang and colleagues (2025) examined how cortisol alters memory by studying the brain as a dynamic communication network. In their study, healthy adults completed two sessions: one after receiving cortisol and another after receiving a placebo. During brain imaging, participants viewed emotionally arousing and neutral images and rated their level of emotional arousal on each trial. Memory for these images was tested later.
Rather than focusing on which brain regions were active, the researchers analyzed connections between regions, known as edges. An edge reflects how synchronized two brain regions’ activity is over time. Stronger synchronization indicates tighter coordination between regions (Huang et al., 2025). By tracking tens of thousands of these connections moment by moment, the researchers identified predictive networks—specific patterns of brain connectivity that reliably predicted either subjective arousal or later memory performance.
At the behavioral level, the results were clear. Under cortisol, higher emotional arousal during learning predicted better subsequent memory, whereas this relationship was weak or absent under placebo (Huang et al., 2025). Cortisol did not improve memory globally; it selectively enhanced memory for subjectively arousing experiences. This explains why stressful situations we encounter, like our first heartbreak, are kept alive in our memories.
Distinct Brain Networks For Arousal And Memory
Neurally, the researchers found that arousal and memory relied on distinct brain networks. One set of connections predicted how aroused participants felt during encoding, while another predicted whether an image would later be remembered (Huang et al., 2025).
Crucially, cortisol affected these networks differently. The arousal-predictive network was stable: the same set of connections predicted arousal under both cortisol and placebo. Cortisol did not change which network represented arousal, but it increased how strongly that network was engaged, particularly during emotional encoding (Huang et al., 2025).
By contrast, the memory-predictive network was reconfigured under cortisol. The specific connections that predicted successful emotional memory differed between cortisol and placebo conditions, indicating that stress alters the neural pathways through which memories are encoded (Huang et al., 2025).
Why These Findings Matter
Together, these results clarify why stress enhances memory selectively rather than globally. Cortisol does not simply strengthen memory circuits. Instead, it stabilizes arousal processing and dynamically retunes memory networks to prioritize emotionally salient information (Huang et al., 2025).
This network-level mechanism has important implications for understanding trauma, anxiety disorders, and stress-related learning. In conditions such as PTSD, overly strong coupling between emotional arousal and memory systems may contribute to the persistence of distressing memories (Joëls et al., 2011).
Under stress, what we remember depends less on which brain regions are active and more on how emotion and memory systems work together.
References
Huang, Y., O’Connor, D., Harris, B. B., Sinha, R., Constable, R. T., & Goldfarb, E. V. (2025).
Dynamic brain mechanisms supporting salient memories under cortisol. Science Advances, 11(50), eadz4143.
Joëls, M., Pu, Z., Wiegert, O., Oitzl, M. S., & Krugers, H. J. (2006).
Learning under stress: How does it work? Trends in Cognitive Sciences, 10(4), 152–158.
McGaugh, J. L. (2004).
The amygdala modulates the consolidation of memories of emotionally arousing experiences. Annual Review of Neuroscience, 27(1), 1–28.