Post-traumatic stress disorder (PTSD) arises after exposure to actual or threatened death, serious injury or sexual violence, and involves persistent re-experiencing, avoidance, negative cognitions/mood and hyperarousal. It reflects lasting changes in fear, memory and regulation networks.

Fear Conditioning and Amygdala

Traumatic events strongly activate the amygdala, creating powerful associations between sensory cues and threat. Later, even mild reminders can trigger:

• Heightened amygdala responses.
• Sympathetic activation (fight/flight) out of proportion to current context.

This underlies intrusive memories and exaggerated startle responses.

Hippocampus and Context

The hippocampus encodes context (where/when events occurred). In PTSD:

• Stress-related glucocorticoid and glutamate toxicity can reduce hippocampal volume and impair contextual processing.
• Fear responses may generalize to safe contexts because the brain struggles to discriminate "then vs now".

Prefrontal Regulation

The medial prefrontal cortex (mPFC) and anterior cingulate cortex (ACC) support extinction learning and top-down inhibition of amygdala. Many studies show:

• Reduced mPFC/ACC activation during trauma reminders.
• Difficulty updating threat associations when reality is safer.

This imbalance (overactive amygdala, underactive prefrontal control) maintains symptoms.

Default Mode and Salience Networks

Alterations in the default mode network (DMN) and salience network may contribute to:

• Persistent self-referential negative beliefs ("я сломан", "мне нельзя доверять людям").
• Hypervigilance to potential threat cues at the expense of other information.

Treatment Implications

• Trauma-focused psychotherapies (e.g. TF-CBT, EMDR, exposure-based approaches) aim to reconsolidate traumatic memories in safer contexts and strengthen extinction learning.
• Pharmacologic options (SSRIs, prazosin for nightmares and others) modulate symptom clusters and support therapy.
• Body-based and grounding techniques help regulate autonomic arousal.

PTSD thus reflects a system-level change in how the brain encodes threat, memory and safety. With appropriate treatment, these networks can reorganize toward greater stability.