How Trauma and PTSD Impact the Brain

Depressed man in the park
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Trauma can impact people in a variety of ways and can even have a lasting impact on the brain. In some cases, it can lead to post-traumatic stress disorder (PTSD), a trauma- and stressor-related disorder that results in improper processing and storage of traumatic memories.

Because of the way these memories are stored, people with PTSD exhibit symptoms such as recurrent memories regarding the event; traumatic nightmares; dissociative flashbacks; hypervigilance; engaging in risk-taking behavior; and an exaggerated startle response.

Not all people with PTSD experience the same symptoms or have the exact same pattern of brain changes. However, researchers have been able to use neuroimaging techniques to look at some of the different areas of the brain that play a role in the development of the condition.

The National Institute of Mental Health reports that an estimated 3.6% of U.S. adults had PTSD in the past year. Approximately 6.8% of all adults will experience this condition at some point in their lives.

Parts of the Brain Impacted by PTSD

Certain structures of the brain are closely related to some of the symptoms of PTSD. These structures include the amygdala and hippocampus (which are part of the limbic system); several parts of the prefrontal cortex (PFC); the mid-anterior cingulate cortex and the right inferior frontal gyrus.

PTSD causes the hyper-activation of some brain structures while other areas become hypoactive.

Both the amygdala and the mid-anterior cingulate cortex become over-stimulated when a person has PTSD. However, the hippocampus, right inferior frontal gyrus, ventromedial PFC, dorsolateral PFC, and orbitofrontal cortex all become hypoactive, some to the point of atrophy.

The Amygdala

The amygdala is a small, almond-shaped region of the brain that plays a role in several functions, including:

  • Some mating functions
  • The assessment of threat-related stimuli (i.e., assessing what in the environment is considered a danger)
  • The formation and storage of emotional memories
  • Fear conditioning
  • Memory consolidation

The Prefrontal Cortex (PFC)

The prefrontal cortex (PFC) is an area of the brain found in the frontal lobe. This region of the brain plays an important part in PTSD. Some of the key functions of the prefrontal cortex include:

  • Emotional regulation
  • Initiating voluntary, conscious behaviors
  • Regulating attention
  • Decision-making
  • Interpreting emotions

The ventromedial PFC helps suppress negative emotions, as well as playing a role in personal and social decision-making. It also plays a major role in the latter part of memory consolidation, as well as regulating extinction—the weakening and eventual dissipation of a conditioned response.

The dorsolateral PFC modulates decision making and working memory. Working memory actively holds transitory information before it becomes part of the long-term memory during memory consolidation.

The orbitofrontal cortex, one of the least understood parts of the brain, seems to be involved in sensory integration and signaling expected rewards and/or punishments in a given situation. It also modulates emotion and decision making.

As a whole, the prefrontal cortex is interconnected to many brain functions, including memory consolidation and regulating slow-wave sleep (non-REM sleep, referred to as "deep sleep").

The Mid-Anterior Cingulate Cortex

The primary function of the mid-anterior cingulate cortex (ACC) is to monitor conflict. The ACC also plays a role in:

  • Emotional awareness (particularly empathy)
  • Registering physical pain
  • Regulating autonomic functions like heart rate and blood pressure

Research has found that decreases in cortical thickness in the ACC are linked to increased PTSD symptoms.

The Hippocampus

The hippocampus helps regulate smell, spatial coding, and memory. More specifically, the hippocampus helps store long-term memories, basically helping to decide what goes from being a short-term memory to what becomes a long-term memory. This process of turning short-term memory into long-term memory is what is referred to as memory consolidation.

Damage to the hippocampus can also release excess cortisol (a stress hormone).

The Right Inferior Frontal Gyrus

The right inferior frontal gyrus is involved in modulating risk aversion. Studies show that transcranial magnetic stimulation (TMS) of this brain region may reduce some risk-taking behavior.

The Brain's Response to Trauma

When your brain identifies some type of threat, the amygdala is responsible for initiating a fast, automatic reaction known as the fight-or-flight response. Think of the amygdala as the alarm that sounds when something poses a danger. This alarm prepares your body to respond, either by dealing with or getting away from the threat. 

The amygdala also communicates with other areas of the brain, including the hypothalamus, which then releases the stress hormone cortisol. It is the brain's prefrontal cortex that must then assess the source of the threat and determine if the body needs to stay on high alert to deal with the threat or if the brain needs to begin calming down the body.

The prefrontal cortex acts as a braking system that helps return your body to a normal state when you realize that the threat doesn't pose a danger or after the threat has passed.

When people have symptoms of post-traumatic stress disorder, the amygdala becomes hyperactive while the medial prefrontal cortex becomes hypoactive.

In other words, the part of the brain that triggers a fight-or-flight response responds too strongly, often in a way that is disproportionate to the danger posed by the threat. At the same time, the part of the brain responsible for calming this reaction does not work well enough.

The Consequences of Trauma

When examining the functions of the various structures of the brain, the correlation between a change in those structures’ activity levels and some PTSD symptoms becomes clearer.

Hypervigilance

The over-activity of the amygdala presents as symptoms of hypervigilance and the exaggerated startle response. Because the amygdala overreacts, norepinephrine is released but then not adequately controlled or dealt with by the prefrontal cortex.

As a result, people with PTSD experience symptoms of hypervigilance. They become overly aroused and are on high alert, which can make it hard to relax and to sleep. A person may feel that they are always tense and even small triggers can lead to react as if they are facing or re-experiencing their original trauma.

Distorted Recall

The hippocampus is involved in explicit memory processes and in the encoding of context during fear conditioning. When the hippocampus fails to function optimally, it impacts the way a person remembers and recalls memories, especially memories that contain a fear element—such as those related to trauma.

In terms of PTSD symptoms, this results in:

  • Recurrent memories regarding the event
  • Distorted negative beliefs
  • Dissociative flashbacks

Impulsive Behavior

Changes to the right inferior frontal gyrus help to explain why people with PTSD may suddenly engage in high-risk activities.

Research has found that reduced cortical thickness in certain areas of the brain associated with emotional regulation and response inhibition, including the right frontal gyrus, is linked to impulse control problems in PTSD.

A Word From Verywell

When thoroughly examining the relationship between brain function and a person's symptoms, it becomes easier to understand many of the complex manifestations of PTSD. Although understanding the brain in this way may not provide direct symptomatic relief to someone living with PTSD, it can be helpful in understanding why the symptoms are happening and, in turn, help the medical community continue to develop more effective interventions.

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