The Limbic System: Structure, Function, and Impact of a Brain Injury
The Limbic System and TBI: Structure, Function, and Impact of a Brain Injury
The limbic system is a network of brain regions that helps regulate emotion, memory, stress responses, and basic instincts. Traumatic brain injury can disrupt the Limbic system in ways that affect mood, recall, behavior, and cognition. The Limbic System acts as the brain’s emotional command center. It is not a single structure but an interconnected system.
For speech-language pathologists, other healthcare providers, brain injury survivors, caregivers, and medical institutions, understanding the Limbic system helps explain why a head injury can change more than physical function. This article discusses the limbic system’s structure, function, and location, and what happens when a TBI occurs.
Structure and Location of the Limbic System
The limbic system is a collection of structures in the brain located on the side of the thalamus, under the cerebral cortex, and above the brainstem. The limbic system has several key components. These are the amygdala, hippocampus, thalamus, hypothalamus, and the cingulate gyrus. These regions work together to process and manage our emotional responses, memories, and some of our body's vital functions. They connect in a way that allows them to communicate and influence each other.
Functions of the Limbic System in Stress Response
The limbic system plays a critical role in our daily lives. For example, with learning, motivation, feelings, and physical stress reactions.
There are 5 main parts of the limbic system:
Amygdala: The amygdala plays an important role in detecting danger and helping the body respond to threats. Epinephrine prepares the body for danger by sharpening senses, and dopamine helps mobilize fight, flight, or freeze responses. This area is also involved in regulating the autonomic and endocrine systems, decision-making, and instinctive and motivational behaviors.
Hippocampus: Responsible for long-term memory formation and memory retrieval. It also plays a role in spatial memory. Chronic stress can impair memory function and reduce the ability to organize past experiences. This allows individuals to keep track of where objects are and of their own position relative to the objects around them.
Thalamus: Relays sensory information and motor signals to the cerebral cortex. Regulates sleep, wakefulness, and alertness.
This area helps manage your:
Body temperature
Blood pressure
Heart rate
Hunger and thirst
Mood
Sex drive
Sleep
Hormones
Feeling of fullness after eating.
Serotonin plays a key role in mood and impulse control. Oxytocin promotes nurturing behaviors and reduces stress hormones. Cortisol increases heart rate and blood pressure during stress.
Cingulate Gyrus: This area plays a role in processing emotions and behavior regulation. It helps support control of emotions. It even helps a person make sense of emotional states, supports insight, and helps regulate autonomic motor function.
The Limbic System and Traumatic Memory in Traumatic Brain Injury
The limbic system's location deep within the brain means it is well-protected by the skull. However, it is not immune to injury. Traumatic brain injuries (TBI), such as concussions or more severe head trauma, can disrupt the Limbic system. The force of impact can damage connections in our brain. People who have experienced a TBI may also develop physical symptoms and longer-term health effects. These may include pain, stomach aches, shallow breathing, and, in some cases, higher rates of serious illness. After a traumatic brain injury (TBI), changes in the brain can cause nerve cells to become overly active, increasing the risk of post-traumatic epilepsy (seizures).
When a person experiences a threat, the limbic system helps recognize danger and triggers a stress response. Their body goes into survival mode, including the “fight or flight” response. If they are unable to escape, that response can become stuck, and trauma lives on through recurring emotional and physical reactions. In the fight-or-flight response, the adrenal glands release stress hormones and shift blood flow to help escape the threat in any way possible. These reactions also affect the nervous system and matter in survival-based treatment. A freeze response can also occur when the system is triggered by a traumatic event. When a traumatic brain injury impacts the function of the limbic system, an individual may experience a variety of symptoms. Individuals may experience emotional disturbances. These disturbances can include anxiety, depression, or mood swings, along with increased fear and stress.Following a TBI, a patient may also experience hormonal imbalances, such as an inability to feel hungry or to feel full after eating an entire meal. Memory and cognitive problems can also be present, as the hippocampusstruggles to form and retrieve memories. A traumatic memory can be reactivated when sensory information is triggered. Common symptoms can include hyperarousal, dissociation, and other body-based stress reactions.
Grounding techniques can help create new neural pathways, and EMDR uses bilateral stimulation to integrate traumatic memories. Talk therapy can help some patients, but healing often requires body-based treatment, as posture can influence emotional experience and touch stimulates the vagus nerve, calming the nervous system. Always discuss treatment options for trauma and other medical conditions with your medical provider.
