The limbic system and its effect on health

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The limbic system is a network of interconnected brain structures located to the side of the thalamus, which is in the center of the brain, and under the cerebral cortex, which is the wrinkly outer layer of the brain. It sits above the brain stem, which resembles a stalk and connects the brain to the spinal cord.

Doctors also describe parts of the brain in terms of lobes. The limbic system is in what is known as the temporal lobe, which sits on each side of the brain, near the temples and above the ears.

The limbic system helps regulate:

• emotional processing
• social processing
• learning
• motivation
• spatial memory

Previously, researchers thought the limbic system was solely responsible for emotional regulation, but today, experts believe it is only one of the parts responsible for this.

The individual parts of the limbic system include:

Hippocampus

The hippocampus consists of two structures on each side of the brain that serve as memory centers. These structures consolidate information, which goes to parts of the cerebral cortex for storage.

The hippocampus forms short-term, long-term, and spatial memory, helping people to navigate their environment. It is also involved in the learning process.

Cingulate gyrus

The cingulate gyrus also helps with emotions, memory, and learning. It specifically links outcomes with behavior, allowing people to see the cause and effect of their actions. As a result, the area may also play a role in the ability to predict adverse outcomes or sensations, enabling people to avoid them.

The cingulate gyrus may control autonomic motor functions, which are involuntary movements, such as those involved in digestion and breathing.

Amygdala

The amygdala lies next to the hippocampus. It is responsible for processing emotions, such as:

• anger
• happiness
• anxiety
• fear

The amygdala also helps with interpreting experiences and creating memories by attaching emotions to them. Other functions include learning to avoid fearful stimuli and contributing to the fight-or-flight response.

The amygdala also has has links with the olfactory system, or a person’s sense of smell. It processes information about smells and tastes.

Hypothalamus

The hypothalamus helps to maintain homeostasis, or a steady internal state. It controls:

• blood pressure
• heart rate
• body temperature
• sexual activity
• thirst
• hunger

The hypothalamus maintains homeostasis by taking information from different parts of the brain, as well as responding to stimuli such as odor, light, and stress.

The hypothalamus also connects to regions of the brain involved in decision-making, creating an “interface” between the emotional parts and the thinking or cognitive parts of the brain.

Basal ganglia

The primary function of the basal ganglia is to regulate involuntary movements, including balance control and eye movements.

The parts of the basal ganglia that lie in the limbic region contribute to emotional behaviors and thinking. They also influence the brain’s reward system and help with reinforcement, which can play a role in habit formation.

Damage to different parts of the limbic system has different effects. For example:

• Hippocampus: Damage to this part of the brain disrupts memory and learning, and it can contribute to dementia symptoms. In Parkinson’s disease, damage here can worsen thinking skills.
• Cingulate gyrus: Harm results in inappropriate emotions, such as a lack of fear. It also causes impairments in learning and pain perception.
• Amygdala: Harm to the amygdala can also affect a person’s fear conditioning, as well as their ability to regulate their emotions.
• Hypothalamus: Damage here causes atypical functioning that links to several mental health conditions. Underactivity may worsen depression, and hyperactivity may cause excessive anxiety.
• Basal ganglia: Harm may result in tremors, atypical postures, and involuntary movements. It also links to movement conditions, such as Parkinson’s disease.

Below are some conditions that may stem from changes in the limbic system.

Epilepsy

In adults, the most frequent type of focal epilepsy is temporal lobe epilepsy, which is the location of the limbic system. The most common cause is damage to the hippocampus, but damage to other parts could also cause epilepsy.

Limbic encephalitis

Limbic encephalitis is a type of brain inflammation that can occur when the immune system reacts to cancer. The symptoms include sudden memory loss, involuntary movements, and dementia-like symptoms.

Kluver-Bucy syndrome

Kluver-Budy syndrome is a disorder that stems from lesions on the amygdala. Many conditions can cause it, including:

• infections, such as from herpes viruses
• trauma to the cerebrum, the principal part of the brain
• Alzheimer’s disease

Manifestations may include:

• visual agnosia, which is when a person can see but is unable to interpret visual input
• hypersexuality, or compulsive sexual behavior
• impassiveness, which is when a person does not show or feel emotion
• eating in excess
• pica, which is when a person craves inedible foods

Dementia

A 2020 study found that a loss of connections between different regions of the brain had associations with a higher risk of cognitive decline and dementia.

The study looked at data from people who did not yet have the condition between 2005 and 2011. They found that the association was particularly strong for those who had a loss of connectivity in the limbic region.

Changes in the structure or activity of the limbic system may play a role in some mental health conditions. For example:

• Schizophrenia: According to a 2007 review of older research, the volume of the limbic system may be smaller in those with schizophrenia.
• Mood disorders: Reduced activity in the limbic system has links to mood disorders, such as bipolar disorder.
• Korsakoff’s syndrome: This is a memory disorder with links to alcohol misuse. Damage to the hypothalamus, which is part of a memory circuit, could be part of the cause.

However, the brain is a changeable organ, and this includes the limbic system. A 2017 review notes there is emerging evidence that psychotherapy can restructure parts of the brain.

Previous research has shown that cognitive behavioral therapy reduces limbic system activity in people with phobias, while cognitive enhancement therapy can improve social and emotional cognition in schizophrenia.

Differences in the limbic system may also play a role in neurodivergence. For example, in older research, scientists found that children with attention deficit hyperactivity disorder (ADHD) have an enlarged hippocampus. This could be an effort to compensate for difficulties in other areas, such as the perception of time.

There are also disruptions in the connection between the amygdala and orbitofrontal cortex, which is responsible for decision-making, in ADHD. This could be part of the cause for impulsivity.

Changes to limbic structures that affect cognition, mood regulation, and social processing may also influence autism, affecting how a person thinks and relates to others.

The limbic system is a network of structures in the innermost part of the temporal lobes. Its functions include emotional and social processing, along with learning and motivation.

Damage to the limbic system can play a role in conditions such as epilepsy and dementia. It may also influence mental health conditions, such as schizophrenia and mood disorders.

However, early research suggests that psychotherapy may restructure areas of the limbic system, helping them to work more effectively.