★   PTSDIY · Field Manual   ★   Part I   ★
Chapter 02
A primer on your brain
The hardware behind the symptoms
FM 02-BRN-101Read time 8 min
Pub. No.FM 02-BRN-101
SubjectNeuroscience
EvidenceStrong
Req. equipmentNone
2-1.Mission brief

Your brain did its job. Under threat, it switched on a survival system built to keep you alive. PTSD is that system stuck in the on position after the threat is gone.

Operator note — Nothing in your head is broken. It is calibrated for a fight that has ended. Calibration can be changed.
2-2.Anatomical reference — the three-part system
PREFRONTAL CORTEX COMMAND · thinks it through AMYGDALA ALARM · fires first HIPPOCAMPUS RECORDS · stamps time
Fig. A — Alarm, records, command · deep structures shown at approximate location
RegionJobWhat trauma does to it
AmygdalaSmoke detector. Scans for threat and fires the alarm before you are aware of it.Becomes over-sensitive. Fires at smells, sounds and situations that only resemble danger.
HippocampusRecords clerk. Files memories with a time and place stamp.Under extreme stress, filing is disrupted. Memories get stored as fragments without "this is over."
Prefrontal cortexCommand. Reasons, plans, and tells the alarm to stand down.Goes partly offline when the alarm is loud. That is why you can't think your way out mid-trigger.
2-3.Why it feels like now

A leading explanation for flashbacks: because the memory was filed without its time stamp, a reminder can pull it up as if it is happening in the present. Your body responds to the memory as if it were the event. That is not weakness or imagination. It is a filing error, and treatment works largely by re-filing those memories with the stamp attached.

2-4.The window of tolerance
HYPERAROUSAL · FIGHT / FLIGHT Racing heart, rage, panic, hypervigilance, can't sit still WINDOW OF TOLERANCE You can feel things and still think. Work happens here. HYPOAROUSAL · SHUTDOWN Numb, foggy, flat, far away, can't move or speak
Fig. B — Where you can operate

Trauma narrows the window. Small stressors push you above it into fight-or-flight, or below it into shutdown. Part II's drills bring you back inside the window. Part III's daily practices make it wider over time.

2-5.Field procedures — find your window
01Name your above signsWrite three things that tell you you're above the window: jaw clenched, scanning exits, snapping at people.3 min
02Name your below signsThree more for shutdown: staring at a screen, losing hours, voice going flat.3 min
03Check in three times a dayMorning, midday, night: above, inside, or below? A mark on paper is enough.30 sec
2-6.Common faults & corrections
✕Fault: "My brain is permanently damaged"Correction: The brain changes with practice and treatment. The same plasticity that wired the alarm can rewire it.
✕Fault: Trying to reason during a triggerCorrection: Command is offline. Body first (Part II), thinking second.
Companion episode — [IN PROGRESS]
PTSDIY · FM 02-BRN-101 · Part I02