Which part of the limbic system plays a key role in the emotions of fear and aggression?

The limbic system is a structure that consists of several different parts, playing critical roles in certain functions we experience daily. We have discovered a good deal about the limbic system and what it’s responsible for in our bodies, such as memories, emotions, and more. Read on to find out just how much we know about this system!

What Is the Limbic System?

The limbic system is a part of the brain consisting of several components such as the hippocampus and amygdala and serving many functions within the body. 

While we have a better understanding today of the limbic system and its role in our day-to-day lives thanks to the progression of neurosciences, our knowledge of what the limbic system does remains incomplete.

Where Is the Limbic System Located?

The limbic system is located in the brain’s cerebrum, which happens to be the largest part of your brain, and directly underneath the temporal lobes.  

What Does the Limbic System Do?

Our limbic system has many roles. 

The primary limbic system function is to process and regulate emotion and memory while also dealing with sexual stimulation and learning. Behavior, motivation, long-term memory, and our sense of smell also relate to the limbic system and its sphere of influence. 

Since the limbic system is linked to the endocrine and autonomic nervous systems, it also plays a significant role in our body’s reaction to stressful situations and environments.

Certain survivalist behaviors are also related to our limbic system. These include our instincts for feeding, reproduction, caring for our children, and responding to fight-or-flight situations. 

Primary Limbic System Parts

The hippocampus, amygdala, and hypothalamus are commonly understood as significant parts of the limbic system: 

Hippocampus 

The hippocampus consists of two parts, with one located in each hemisphere of the brain. The name hippocampus comes from a Greek word relating to its shape: that of a curvy seahorse. 

In essence, the hippocampus is the control center for our memory. In the hippocampus, episodic memories are made and stored across the cerebral cortex. Aside from this, the hippocampus also has connections to both learning and emotions.  

The hippocampus is located in the temporal lobes, directly above the ears, and is one of the most researched parts of the brain. In addition, the hippocampus helps generate new neurons and is one of the few places where this process, known as neurogenesis, occurs. 

While the hippocampus was historically believed to be closely related to our sense of smell, that notion has since been largely debunked. However, since certain smells can be associated with memories, such as the smell of pumpkins and cinnamon being associated with autumn, or chestnuts being associated with wintertime or Christmas, there is at least some evidence that the hippocampus and our sense of smell have some connections. 

Besides its role in memory formation, the hippocampus is also responsible for spatial memory and navigation and the transfer of long-term memories. Due to its relation to memory, specific symptoms can occur when the hippocampus is damaged or the hippocampus malfunctions. These symptoms include: 

• Mild to severe memory impairment 
• Disorientation 
• Short-term memory loss 
• Forgetting things like directions, locations, and words

Alzheimer’s disease has specifically been associated with damages sustained to the hippocampus. 

Amygdala 

The almond-shaped amygdala shares a few similarities to the hippocampus. It is located next to the hippocampus structure and plays a role in forming new memories and works with the hippocampus to attach emotions to such recollections.  

However, the primary purpose of the amygdala is to control and regulate emotions and emotional responses. This includes feelings such as fear, anger, and happiness. In addition, due to its connection to memories and emotions, the amygdala plays a significant role in forming strong memories. For example, memories driven by emotion are formed into long-term memories that stick, whereas those with little to no emotional content are often forgotten. 

The amygdala is also responsible for emotional learning and certain mental health disorders such as social anxiety and addiction.  

The following symptoms can occur when the amygdala is damaged: 

• Difficulty forming emotional memories 
• Intense responses to fear 
• Sensitivity to emotions 
• Feelings of anxiety, aggression, irritability, etc. 

Hypothalamus 

The primary responsibility of the hypothalamus is homeostasis: helping the body maintain a steady internal state. The hypothalamus also acts as a control center for autonomic functions. These functions include hunger and thirst, blood pressure, body temperature, and more. 

In addition, the hypothalamus regulates sexual motivation and behavior and responds to stress. The hypothalamus works with various stimuli, including light, arousal, stress, and odor, to control its functions. 

Damage to the hypothalamus can result in aggression, stress, fatigue, hypothermia and hyperthermia, changes in weight, and an overactive or underactive sex drive. 

Secondary Limbic System Parts

A few structures are thought to be closely connected to the limbic system instead of being involved as primary components. These structures include:

• Cingulate Gyrus: The cingulate gyrus is responsible for emotional regulation, certain behaviors, pain, and autonomic motor functions. Additionally, this structure plays a significant role in response to fear and negative situations. Therefore, impairment of the cingulate gyrus could result in inappropriate emotions, learning impairments, a lack of fear, and more.
• Ventral Tegmental Area: The ventral tegmental area affects dopamine and pleasure. When damage to this structure occurs, it becomes difficult to experience joy, and often, alcohol, drugs, and gambling are used as coping mechanisms.
• Prefrontal Cortex: Like the ventral tegmental area, the prefrontal cortex is a pathway for dopamine and plays a significant role in pleasure and addiction. Aside from that, the prefrontal cortex is also involved in future planning and action.
• Basal Ganglia: The basal ganglia consist of various structures between the forebrain and midbrain. The primary responsibilities of the basal ganglia include regulating voluntary movements such as eye movements and helping with balance and posture. Other duties of the basal ganglia include rewards, repetitive behaviors, and focusing. Basal ganglia impairment can result in disorders such as Parkinson’s and Huntington’s disease, tremors, abnormal posture, and involuntary muscle movements.