The Defense Cascade

When did you first learn the temperature of a body? I mean the one humming under the skin, not the lips and cheeks that chap in a snowstorm. Was it when you first felt sick, wrong, burning, that you discovered what you should be and had not been? Who told you? Was it a white coat black snake metal medallion on your chest, or your mother’s fingertips, or a plastic stick under your tongue? Or was it when you first touched another body and were touched, felt their heat flow into you like electricity at your poles?

Growing up, my mother could always tell when I had “a temperature.” She would lean in, cradle the back of my neck in her palm, and press her thin lips to my forehead. They felt cool, dry. Like polished granite. My eyelids would droop involuntarily as I breathed in the cashmere scent of her, suspended in the moment before the verdict. In those lingering seconds, I was just a body. Neither here nor there, neither sick nor well.

We once had no methods to quantify heat. Before the seventeenth century, we—meaning Aristotle—defined matter on a two-by-two matrix: hot and cold, dry and wet. There were no degrees. These qualities simply were or were not. Galileo’s thermoscope—one of the earliest devices created to measure heat, the precursor to the thermometer—had no numerical scale and could only symbolize temperature variation, which is to say that Galileo could show its rise and fall without knowing exactly where it stopped. He is said to have used his hands. Between his palms, he warmed a small glass bulb attached to a long, slender straw, which he positioned straw-side-down in a decanter filled with several inches of water. As the heat from his hands ebbed away, the air molecules within the bulb would contract, drawing water up the wheatstalk-thin stem from the vessel below to fill the void.

Within twenty years, the next man playing god would take the thermoscope and stick some numbers on the side. Still, something resonates about Galileo’s early changemeter. Normal is undetectable; change is how we know our insides. We only experience living just shy of one hundred degrees once we cross fever’s threshold. And in a broader sense, doesn’t process matter more to us than result? We can name and represent our transmutations without knowing where—or what—we are. We can write about journeys we are still on. We should.



Vignette 1: Arousal


A twenty-three-year-old writer is sitting in her St. Louis apartment on a winter night when she begins to feel unusually cold. She repeatedly takes her own temperature with a green plastic thermometer. After ten minutes, the digits on the plastic stick read ninety-four degrees. She starts to present characteristic physiological symptoms of the ‘arousal’ fear state, including an elevated heart rate, hyperventilation, and a rising wave of alarm. For the duration of the panic attack, she believes that she will die of hypothermia.


I’d graduated from college the previous May and moved seventeen minutes away from campus into an apartment with my best friend. Beyond our living room windows, the night was as glossy and black as my nail polish, the asphalt slick with melted snow and the vacant white light from the streetlamps. I was wearing thick gray sweatpants and two sweatshirts with a long-sleeve shirt underneath. I remember clutching the thermometer in my fist, light and breakable as a child’s toy. I remember shivering until my bones jangled in their sockets, my throat tight and full, as though I were choking on my heart. A sense of caving in, like a riven glacier, all my substance sloughed off in sheets.

During the climb toward the zenith of my anxiety disorder four years earlier, in my sophomore fall, I felt constantly cold. A pervasive fear had begun to burn constantly at the base of my throat as if I’d swallowed an ice cube, and as a result, I ate less and less. At the time, I didn’t make the connection between my clammy extremities and my empty stomach. I’m just a cold person, I would say, as if temperature were a personality trait. I only woke to my hollowness once I slipped below a hundred pounds, like the opposite of a fever.

In the days and weeks after the sudden, random panic attack, I wondered why it had happened. I was happy, I thought. I had gone to therapy regularly and been considered ‘recovered’ in disordered eating terms for so long that I rarely thought about that period of my life (though I’d be lying if I said it didn’t still throb beneath my skin like a heartbeat, audible sometimes in moments of quiet or times of rapid change). Now, I loved—and was loved by—a new boyfriend, a towering artist with quinine-bright eyes and a three-legged pit bull, a boy who, when I showed up at his door with chattering teeth, swaddled me in a blanket and pressed my burrito body to his chest while we watched Breaking Bad and waited as my temperature crept toward normal. Besides, even when my anxiety was at its worst, I never had panic attacks.

Panic exemplifies the initial phase of “the defense cascade,” a series of instinctual fear states we move through in reaction to threatening stimuli. Chains of neural impulses trickle down from the brain through the spinal cord in four main stages: arousal, fight or flight, freezing, and tonic (or collapsed) immobility. The defense cascade is what quite literally sends a shiver down our spines. We feel fear in our bodies as a chill, a shudder. Fear is cold because cold means death, or at least its approximation, like passing through a chiffon specter, or someone treading on your future grave. After life leaves, during what’s called algor mortis—the “death chill”—warmth gradually deserts the bloodstream until the body becomes a room temperature brick of gristle and fat.

Panic, on the other hand, is hot, fast, roiling. Heat might commonly prevail in accounts of anxiety attacks and disorders, but in states of arousal, both extremes—fire and ice, magma and marble—can manifest. One can become the other. The amygdala—the part of the brain associated with fear, and one of the primary arbiters of the defense cascade—signals the body to flood the bloodstream with adrenaline and cortisol, which narrow the blood vessels, causing spikes in body temperature. However, if we begin to sweat, we sometimes cool the body to excess. Hyperventilation also has the potential to cause chills and freezing sensations in the extremities. When we rapidly take in too much oxygen, blood flow stagnates, lagging before it reaches the parts of us furthest from the heart.

The defense cascade is not actually as linear as the name suggests. The four fear states feed into one another in a call-and-response cobweb billowing out from a single vertex, the initial activation of the hypothalamus and amygdala. Arousal can directly trigger fight or flight, or it can delay the verdict until after the freezing stage, in which the animal (or human) stiffens to gather information and avoid detection. Freezing is especially common in predator-prey interactions—imagine a stock-still doe, a rat tensed mid-step. This is distinct from tonic immobility, a state akin to playing dead. Tonic immobility is the only response in the defense cascade that studies have proven to be associated with a drop in body temperature. Unlike freezing, this stage is not a delay but an absence, a surrender after fighting and fleeing have failed.

All stages of the defense cascade can be primed by experience, meaning that fear responses are more likely to be activated after repeated exposure to frightening or traumatic stimuli, even in the absence of a real external threat. This is another way of saying that when we panic for no reason, there may be a reason.



Vignette 2: Freezing & Fight or Flight


A twenty-two-year-old bartender with eyes like grottoes attends a Halloween party, where he consumes an unspecified amount of alcohol. Later that night, he migrates to a bowling alley with his coworkers. His girlfriend arrives. He drives her back to his apartment, or almost, because when they crest the hill a few blocks from his place he forgets to brake—in fact, he accelerates—and crashes his car into a stopped sedan at the intersection. He won’t remember any of this. His girlfriend will remember for him. Time stops as the airbags deflate and they just sit there, the two of them, inert, scanning their bodies for breakages. They are both fine. When the smoke clears enough for him to see, he throws the crumpled coupe in drive and peels away from the scene of the accident with a rubber scream and takes them as far as he can before the car gives out forever. The morning after the accident, he shows up at his girlfriend’s apartment. He is crying; he doesn’t know how she got home, doesn’t know how they survived. He pukes in her toilet twice from the effort of fighting for them.


What was good, light, warm: Christmas Eve at his grandfather’s house a few months later, when the whole family exchanged gifts and his dad gave me a bar of dark chocolate, my favorite. Catching his eye at the opening of an art exhibition on Cherokee Street and seeing my sparkle reflected there. Catching his eye at a punk show two weeks later on the same block. Walking from the show to his friend’s car and realizing that they were both wearing camel-colored wool coats that fell to their knees, hilariously formal coupled with their unbrushed nipple-length hair and double-cuffed beanies and cigarette smoke forever tattooed on their skin. Watching Breaking Bad as a burrito on his couch that terrible February night, a show where everything feels cold in spite of the desert setting—the sand like marble, the hard blue sky, the cacti like living fossils. How I stopped shivering after a few episodes, how I could breathe normally after a few more. I couldn’t explain why it helped until later, when I read in The Collected Schizophrenias about sufferers of post-traumatic stress disorder who sought out stimuli like violent movies as a way to externalize the war raging in their veins and minds and heart.

Looking back, I can hazard at other reasons for the backslide, if that’s what it was. Earlier that month, I had quit my regular serving job to increase my hours freelancing for a local magazine, which meant I’d lost my grounding in any semblance of routine. With no office to clock in to, nowhere really to be, I felt the walls of my apartment drawing closer. Though I dismissed seasonal affective disorder back then, the dearth of light was getting to me as February drew to a close. Three months had passed since the accident with the fluorescent-eyed boy. Its bruising had begun to show. At red lights and stop signs, sometimes I would suddenly start to sob, gripping the steering wheel with both hands so hard that my knuckles glowed bone-white through the skin. It took almost a year for me to begin to read into PTSD, about the myriad ways that trauma and anxiety clog the body like hair in a shower drain. How the body remembers, even when the brain will not.



Vignette 3: Tonic Immobility


Anne Greene is a twenty-two-year-old domestic servant living in Oxford. The year is 1650. For a time, she is pregnant, after being sexual assaulted by her master’s grandson. Anne gives birth to a stillborn child. As a result, she is charged with murder and sentenced to death. The day of the hanging is especially cold, the kind that aches in the roots of your teeth, freezes the drippings in your nose and draws the skin of your cheeks taut. Anne swings at the end of her rope for almost half an hour and sustains severe blows to ensure that she is really dead. The following day, medical students preparing the body for dissection find her heart still beating. Her pulse is faint but steady. Anne’s full recovery is regarded as an act of divine intervention that proves her innocence, and she receives a full pardon. She returns to society and even goes on to marry and start a family. Fifteen years after her resurrection, however, Anne dies in childbirth.


Few have studied the way human beings experience the final fear state, tonic immobility, sometimes glibly likened to “playing dead.” In their 2014 article “Fear and the Defense Cascade,” Kozlowska et. al. explain that tonic immobility can result from a variety of scenarios: “when the individual is cornered and perceives that neither escape nor fighting is possible; as a response of last resort when… flight or fight is not possible or has failed; or as the individual’s first-line response to trauma (or to recurrent memories of trauma).” Symptoms include “disturbances in the perception of space and time, abnormal visual experiences, disturbances in body-image perception, and depersonalization and derealization in humans,” as well as “fear, immobility, coldness, numbness and analgesia, uncontrollable shaking, eye closure, and dissociation… as well as a sense of entrapment, inescapability, futility, or hopelessness.” This state of shutdown is commonly described both by those experiencing a direct physical threat and those with post-traumatic stress disorder. Notably, one of the few studies conducted on the subject, published in 2017 by the Karolinksa Institutet in Sweden, centers on the high frequency of tonic immobility in survivors of sexual assault.

Humans are far worse at recovering from fear responses than animals. We create representative heuristics, imprints of our trauma that live on in our brains and muscles and spider-silk nets of nerve endings. Recovery, like the defense cascade, is not linear. Leslie Jamison wrote, “Trauma bleeds. Out of wounds and across boundaries. Sadness becomes a seizure.” The body remembers. I believe that Anne Greene’s did. We can grow around the damaged pieces like muscle around shrapnel, but the remains would be there, whole, if you flayed us open.

I didn’t know this on the evening of my panic attack, but according to the medical definition of hypothermia—when the body loses heat faster than it can produce it, causing body temperature to fall below ninety-five degrees—at 94.0, I was hypothermic. Hypothermic states are, understandably, dangerous. Extreme cold can allow infections like pneumonia to proliferate and can slow the heart to a pace approximating near-death. But it’s also the reason Anne Greene survived her attempted execution. For five thousand years, the medical community has taken interest in hypothermia as a method to delay death and even prevent it. The oldest known medical text, the Edwin Smith Papyrus of Ancient Egypt, made multiple references to cold as therapy. Hippocrates recommended ice packing to prevent blood from rushing to wounded limbs, which Napoleon’s army surgeons would apply centuries later as a natural anesthetic prior to amputation. In recent years, doctors have begun to conduct more studies into how hypothermia can act as a neuroprotective agent by slowing blood flow to the brain, insulating the organ from further damage after an acute injury. Cold can terrify, but it can also rescue. It kept Anne alive, even if her flame soon sputtered out.

There are some experiences that change our composition inside, as in a chemical reaction. These processes can be grand, sudden, like nuclear fission or a volcanic eruption, which can chill the entire globe for years after the blast in what’s known as an “impact winter.” Or there can be a gradual kindling, a slow gush of heat as metal corrodes into rust. One trauma can awaken another, melting the ice that fossilized our fear, that both silenced and preserved it.

One of my favorite poems starts like this: On a single night / Not even near to freezing… Howard Nemerov wrote “The Consent” about the small grove of ginkgo trees behind my college library, about how at the first sign of frost, the ginkgo—unlike almost any other tree that sheds its fall plumage—drops all its leaves at once. As fall crept in, I’d wait with quiet anticipation for the first cold snap. The next morning, the ground would be shellacked in yellow, the trees blank and gaunt. I’ve realized that I too wanted to know: What signal from the stars? Maybe the accident had snapped something in me like a sudden chill, sending a shiver out my petioles in a cascade of golden leaves and exposing, for a brief moment on a glossy black night, my skeleton.

The terror still returns, sometimes: when I have just eaten and am still hungry, when I have not eaten in a long time, when I curl the pads of my fingers against the inside of my palm and feel a frigid kiss, like an iron handrail in the shade or the cool substratum of beach-sand you have to burrow to reach.

Fear responses—like pain—try to preserve us in the face of danger. In a way, I have to be grateful for the defense cascade, for the way my body remembers and reminds. For the warning signals that frighten, for my new flight pattern, or lack thereof. I tell myself that next time, if there is a next time, I won’t flee into my recesses.

This is the tricky part: weighing the waterfall against the reality of my situation, which is that I’m fine, mostly. I’m good. Like Galileo and his primeval thermoscope, it’s difficult for me to pinpoint or quantify my output, the result of this experiment. So I start over, and choose new beginnings. Places from which to expand.