Brakes screech at the end of the alley. A person sitting on the front porch drinking tea freezes, hand gripping the cup, heart pounding. Only a second or two later do they turn to look: it is just a motorbike stopping to let a child cross the road. A few years ago, the same sound of brakes came right before a collision that broke their arm. The bone healed long ago, and they can tell the story of that day calmly.
Two routes for an alarm signal
Sounds and images from the ears and eyes first reach the thalamus, a relay station deep in the middle of the brain. From there the signal splits into two routes. The first goes up to the cerebral cortex, where the sound is analyzed carefully: what it is, where it comes from, whether it is worth worrying about. This route is accurate but takes extra time. The second route is shorter and carries the signal straight to the amygdala, a small almond-shaped mass deep in the temporal lobe on each side of the brain.
The amygdala does not wait to know for sure. A rough outline, like a screech or something long and curved under your feet, is enough for it to sound the alarm: a racing heart, quick breathing, tense muscles, a body frozen in place. A moment later, once the cortex has finished its analysis and found nothing dangerous, the reaction calms down. Neuroscientists often call this short route the thalamus–amygdala shortcut.
According to a review by LeDoux (2000), most of what we know about the emotion circuits in the brain comes from research on fear. The amygdala helps store and recall fear memories, and what has been found about it in laboratory animals also holds true for the human brain.
Fear clings to things that look alike
Bitten by a snake once, afraid of rope for ten years. A rope never hurt anyone, but its long, curved shape looks enough like a snake to set off the alarm before the eyes can recognize it as a braided rope.
In the laboratory, this is studied under the name fear conditioning. A harmless signal such as the sound of a bell, if it comes just before a frightening stimulus only a few times, can later make an animal freeze and its heart race from the bell alone. In people, the reaction also spreads to the setting where the event happened: someone bitten by a snake while stepping into a pile of dry leaves may afterwards be wary of every pile of leaves. Even knowing full well that the rope is harmless, people still flinch.
A learned fear response can fade
When the old signal comes back many times without anything bad following it, the fear response gradually weakens. Researchers call this fear extinction. The neural circuits behind this process have been studied for ten years in both rats and humans and are used as a model for treatment approaches (Milad and Quirk, 2012). The old memory is still there; the nervous system has simply learned on top of it that the signal is now safe. When you are tired or under stress, the old reaction can come back.
When the alarm threshold is set too low
A sensitive amygdala helps people escape real danger. Trouble starts when it goes off too easily, even for things that are not frightening at all, so the body stays ready to fight or flee all day long. At the examination desk, people in this state often describe:
- Jumping at ordinary noises such as a door closing or a phone ringing;
- Palpitations, with the heart racing at times for no clear reason;
- Light, broken sleep, waking easily in the night;
- Long-lasting tightness in the neck, shoulders and jaw, and frequent headaches;
- Tiredness even without doing anything strenuous.
Thyroid disease and heart rhythm disorders can cause similar signs, so the doctor rules them out first. If you have pain that stays in one spot despite trying many treatments, you may want to read more about how old emotions help keep pain going.
Startling along with these signs: see a specialist
A past event may have left trauma behind and needs assessment by a psychiatrist if you have:
- Repeated nightmares about the event;
- Flashbacks, where the past comes back so vividly it feels like it is happening again;
- Long-lasting avoidance of places, people or tasks that bring back the memory, to the point that it affects daily life;
- Repeated panic attacks: a pounding heart, shortness of breath, trembling, a feeling that you are about to die or lose control.
If you have thoughts of harming yourself, even fleeting ones, tell someone close to you and go to a medical facility today. Palpitations with chest pain or fainting mean going to the emergency department first.
The consultation starts with the sound that makes you jump
The first thing the doctor asks is which sounds make you jump, and when it started. Only then come the clinical examination and the four examinations of traditional medicine, with lab tests when needed.
To find out how strongly an old memory still activates the nervous system, Dr. Dinh Ngoc Duc (MD, MSc in Traditional Medicine) uses Applied Kinesiology (AK). The doctor chooses a muscle that is holding strong, then asks you to picture again a situation that often makes you jump, such as the sound of brakes or deep water. You only need to hold the image in your mind for a few seconds; how much you say about it is up to you. While you think about the sound of brakes, the doctor tests that muscle again. If an arm that was holding firm suddenly gives way, it is a sign that the memory is still having an effect. The test rests on the foundation of muscle testing in diagnosis.
The doctor also checks the primitive reflexes. These are reflexes present from birth, such as the Moro reflex: when a baby feels a sudden drop, it startles and flings both arms out. As the nervous system matures, these reflexes are integrated and quiet down. At the examination desk, the doctor sees some adults under heavy stress whose reflexes have become active again, making them startle easily and find it hard to relax.
Once it is clear which memories and which reflexes are contributing, the doctor uses AK stress techniques to help the nervous system lower its level of reaction. Over the sessions, the doctor checks whether the muscle still holds strong when you think back to the old situation. The Su Wen (素问 / 素問, Basic Questions) says that fear makes qi descend and fright throws qi into disorder. So for people who startle easily and have palpitations with restless sleep, the doctor chooses acupuncture points and herbs for an herbal decoction aimed at calming the mind and targeting the Heart and Kidney, depending on the pattern, then gives guidance on exercise suited to your strength.
Worth keeping
- Write down which sounds and places make you jump, and what they remind you of;
- After each startle, sit down and breathe slowly until your heart settles;
- Keep regular sleep hours while you are under stress;
- If you are being treated by a psychiatrist, bring your prescription to the consultation, and don’t stop your medication on your own;
- If nightmares, flashbacks or avoidance go on for a long time, see a psychiatrist early.
If you take psychiatric medication or sleeping pills, tell the doctor before starting an herbal decoction, and do not stop your medication on your own.
References
- LeDoux JE (2000). Emotion circuits in the brain. Annu Rev Neurosci 23:155-84. https://doi.org/10.1146/annurev.neuro.23.1.155
- Milad MR, Quirk GJ (2012). Fear extinction as a model for translational neuroscience: ten years of progress. Annu Rev Psychol 63:129-51. https://doi.org/10.1146/annurev.psych.121208.131631
