HIPPOCAMPAL NEURAL SIGNALS OF THREAT EVALUATION IN MARMOSETS (CALLITHRIX JACCHUS)

Fear is a defensive state that coordinates behavioral and physiological responses to environmental threats. While studies in rodents have substantially advanced our understanding of the neural circuits supporting fear, comparatively little is known about how the primate brain processes and responds to aversive visual cues. Addressing this gap is critical for elucidating how the perception of danger gives rise to threat-related behaviors, and for developing experimental approaches that identify when animals experience threat and how fear memories are expressed. To link behavioral responses with underlying neural activity, behavioral and electrophysiological data were acquired simultaneously using a custom synchronization system that temporally aligned stimulus presentation, video recordings, and neural signals. In this study, we evaluated defensive behaviors and hippocampal oscillatory dynamics in marmosets exposed to aversive and neutral visual stimuli. We found that threat exposure induced sustained visual engagement with the stimulus, increased avoidance behavior compared to neutral conditions, altered vigilance, and enhanced hippocampal gamma-band activity. Together, these findings suggest that the hippocampus is engaged in online threat evaluation and provide a framework for investigating the neural mechanisms underlying defensive behaviors in primates.