Flaying, burning, boiling, crushing, beating, ripping, and stabbing—the horror of physical torture throughout history is still cringe-worthy centuries later. But what about the effects of such torture on the brain? It’s time to take a look at the effects of torture from inside the cranium.
Before we strap ourselves to any racks or pulleys to find out what’s going on, here’s what we already know about the brain’s stress response. When exposed to a physical or mental threat, the brain goes into fight or flight mode. In this state of hyperarousal, the stress hormone cortisol binds to glucocorticoid receptors in the hippocampus and prefrontal cortex, inciting neuronal activity by increasing Ca2+ access. The brain also releases catecholamines, hormones involved in glucose release, blood pressure increase, and heart rate increase.
These short-term effects often have long-term consequences. According to Dr. O’Mara of the Neuroscience Institute at Trinity College in Dublin, the amygdala, which is “involved in the processing of fear- and threat-related stimuli,” will increase in size, “creating a negative feedback loop that amplifies the effects of subsequent stressful events.” If torture continues over an extended period, the brain might suffer irreparable tissue damage in the hippocampus and prefrontal cortex. Recent imaging studies of the brains of modern torture victims suggest a correlation between extreme stress and over-activation of the frontal and temporal lobes, a phenomenon which in turn reduces verbal memory and recall abilities.
The effects of torture on the brain proved as colorful and creative as the methods themselves. We’ve focused on three of the most stressful and agonizing tortures of history and their horrifying effects on the mind.
Cause of death: a combination of asphyxiation, heart failure, blood clotting in the lungs, and hypovolemic shock. Sound painful enough yet? The physical pain was just the beginning. Forced to support their own body weight with their chest and rib cage, victims would experience lung compression and oxygen starvation, or brain hypoxia. Within seconds, cognitive functions began to fail and victims experienced headaches, light-headedness, dizziness, and increased breathing rate and sweating. Next, cyanosis would take effect, coloring the victim’s lips, mouth, and fingertips blue due to de-oxygenation. A loss of control and mobility known as myoclonus likely ensued. Oxygen starvation would stress the entire brain, but the hippocampus, and the basal ganglia and cerebellum would have been most sensitive to damage. The dual agony of mental and physical pain makes crucifixion possibly the most agonizing method of torturous execution in history.
Although these methods were often used to force confessions, they actually had the adverse effect of crippling memory mechanisms
Heretic’s Fork and Sleep Deprivation
Medieval torturers were resourceful in crafting deceptively simple torture devices, such as the heretic’s fork: a convenient strap around the victim’s neck that forced two extremely sharp prongs into the flesh of the throat and chin. The main goal of this torture was sleep deprivation: whenever the victim would start to fall asleep, the prongs would puncture the skin and force the victim awake. 
Without sleep, the brain has no time to regulate its supplies of epinephrine, dopamine, and serotonin. Neurotransmitter disruptions can cause extreme mood swings, volatility, and a reduced tolerance for pain. Although the heretic’s fork has faded from use, sleep deprivation has survived as a torture tactic. Soviet gulags were renowned for forcing sleep deprivation on their prisoners. As one survivor Alexandr Solzhenitsyn described, “Sleeplessness befogs the reason, undermines the will, and the human being ceases to be himself, to be his own ‘I.’”
Also known as dilutional hyponatremia, torturers would force their victims to ingest copious amounts of water, causing nausea, vomiting, blurred vision, severe headaches, exhaustion, muscle pain, and loss of coordination and mental clarity. In response to this overabundance of water, the body’s cells compensated by absorbing the water to increase the concentration of sodium, an essential electrolyte, in the body’s fluids: this swelling resulted in irreparable damage. The effect on brain cells is especially severe. The rigid structure of the skull creates additional pressure on the cells of the brain, making them more likely to burst. It is this brain damage that eventually leads to the death of the victim. 
For centuries, dozens of cultures used crucifixion, the heretic’s fork, and water intoxication to torture and interrogate prisoners. Though undoubtedly agonizing, the mental pain and psychological damage also proved excruciating to the victims. Ironically, although these methods were often used to force confessions, they actually had the adverse effect of crippling memory mechanisms, so records of their ineffectiveness are no surprise. The potential for brain manipulation, however, was immense—so immense that we have only just begun to comprehend what actually occurred in the victims’ brains.
References: http://www.sciencedirect.com/science/article/pii/S1364661309001995  http://channel.nationalgeographic.com/killing-jesus/articles/how-did-crucifixion-kill-a-person/  http://www.memorylossonline.com/glossary/hypoxiaanoxia.html  http://www.planetdeadly.com/human/medieval-torture-devices  http://www.theatlantic.com/health/archive/2013/12/how-sleep-deprivation-decays-the-mind-and-body/282395/  http://meoantolin.hubpages.com/hub/How-drinking-too-much-water-can-kill-you