The brain is a complex structure that is made up of many parts/structures that vary in size, purpose, and functioning. A small structure, known as the Caudate Nucleus, plays a significant role in several important functions despite its size. So, what is the Caudate Nucleus?
Small in size, the Caudate Nucleus is considered the major input station of the Basal Ganglia. The Caudate Nucleus is responsible for several motor and cognitive functions. This structure consists of many interneurons and dopamine neurons essential for successful functioning.
Although the Caudate Nucleus is not one of the most popular or well-known parts of the brain, it should be. To learn more about this structure, keep reading! Below we discuss the location, the physiological make-up, the purpose, function, and dysfunction of the Caudate Nucleus.
The Structure And Location Of The Caudate Nucleus
The Caudate Nucleus comprises three parts, namely the head (caput), the body (corpus), and the tail (cauda).
- The head (caput) of the Caudate Nucleus. This part of the Caudate Nucleus makes up the lateral wall of the lateral ventricle.
- The body (corpus) of the Caudate Nucleus. The Caudate Nucleus's body lies lateral to the lateral ventricle's body.
- The tail (cauda) of the Caudate Nucleus. Above the lateral ventricle's temporal horn lies the tail of the Caudate Nucleus.
The Caudate Nucleus's head and body form part of the lateral ventricle's anterior horn floor. The body runs towards the back of the head, where the tail slightly curves back toward the anterior to form the lateral ventricle's inferior horn roof.
The Definition Of The Caudate Nucleus
The Location Of The Caudate Nucleus
Within each hemisphere of the brain, one can find a Caudate Nucleus. This means there are two in total, one on each side of the brain. The Caudate Nuclei are located in the center of the brain, below the Cerebral Cortex and next to the lateral ventricles.
The Caudate Nucleus is also next to the Putamen. Bridges of grey matter link these two structures.
The Physiological Makeup Of The Caudate Nucleus
The Caudate Nucleus consists of medium spiny neurons that use GABA as their primary neurotransmitter. The axons of these neurons travel to other Basal Ganglia parts/components.
Other neurons exist within this part of the brain; they are listed below:
- Cholinergic and GABAergic interneurons.
- Dopaminergic neurons which use the neurotransmitter dopamine.
The Purpose And Function Of The Caudate Nucleus
The Caudate Nucleus is part of the Basal Ganglia, a group of subcortical nuclei responsible for many cognitive and emotional functions and body movement. The purpose of the Caudate Nucleus is to control voluntary movements and the brain’s learning and memory system.
The Motor Function Of The Caudate Nucleus
Accomplishing movement requires the Basal Ganglia to receive information from the Cortex regarding movements that have to be made. The information first travels via a pathway known as the Corticostriatal Pathway to the Caudate Nucleus, as this structure is one of the primary input nuclei for the Basal Ganglia.
The Neurons in the Caudate Nucleus extend to other parts of the Basal Ganglia. These neurons contain the neurotransmitter GABA, responsible for creating pathways to facilitate movements.
The Cognitive Function Of The Caudate Nucleus
The Caudate Nucleus’s anterior portion connects with the lateral and medial prefrontal cortices. Together, this small structure is responsible for working memory and executive functioning.
- Working Memory. Working memory can be described as a short-term storage mechanism that assists with various cognitive activities such as thinking, reasoning, decision-making, and language comprehension.
- Executive Functioning. Executive functioningis the mental process that assists with planning, remembering instructions, focusing, and paying attention.
The head of the Caudate Nucleus controls these cognitive functions as this part is seen as this structure's cognitive and emotional portion. The head of the Caudate Nucleus is connected to the medial frontal pole. The middle section of the Caudate Nucleus is responsible for receiving input from the prefrontal cortex.
Furthermore, the Caudate Nucleus is also responsible for the Association learning function. The Caudate Nucleus's body and tail control learning acquisition, while the head is responsible for processing feedback on learning trials.
- Association learning. Association learning is a process that involves acquiring information about relationships between events or entities in one’s environment.
Other Cognitive Functions Of The Caudate Nucleus:
- Goal-directed action.
- Sleep.
- Emotion.
- Language.
- Threshold control.
Lesions On The Caudate Nucleus
The term "lesion" refers to any type of damage to the brain which is caused by disease, trauma, or birth defects.
Hemorrhages and strokes mostly cause lesions to the Caudate Nucleus. However, hypercholesterolemia and diabetes also contribute significantly to potential lesions to the Caudate Nucleus.
The symptoms of lesions caused by hemorrhages:
- Headaches
- Emesis
- Nuchal rigidity
- Ocular motor deficits
- Dysarthria
- Abulia
The symptoms of lesions caused by strokes:
- Aspiration issues
- Cognitive dysfunction
- Motor deficits
- Speech deficits
- Abulia
- Confusion
- Paresis
- Akinesia
- Disorientation
What Disorders Are Associated With The Caudate Nucleus?
There are several disorders that researchers found to be linked with the Caudate Nucleus. Below we discuss various disorders that cause significant damage to this structure, as well as some that are caused by the dysfunction of this structure. The disorders that we will focus on and explore in more detail include:
- Alzheimer’s Disease.
- Parkinson’s Disease.
- Huntington’s Disease.
- Attention-Deficit Hyperactivity Disorder.
1. Alzheimer’s Disease
Alzheimer’s Disease is a common progressive brain disorder that gradually destroys memory and thinking skills, resulting in the inability to carry out basic tasks.
With Alzheimer's Disease, damages first occur in parts of the brain that are responsible for memory, such as the Entorhinal Cortex and Hippocampus.
- Entorhinal Cortex. The Entorhinal Cortex is located in the medial temporal lobe of the brain. It is responsible for various functions, such as being a hub for memory, navigation, and the perception of time.
- Hippocampus. The Hippocampus is located deep in the brain's temporal lobe and plays a significant role in learning and memory.
As this disease progresses, damages become more significant, with the Cerebral Cortex being the next target. The areas in the Cerebral Cortex that become damaged are responsible for social behavior, reasoning, and language.
Furthermore, as a progressive brain disorder, Alzheimer’s Disease has different stages. With each stage, the symptoms are different. These stages include:
- Mild Alzheimer’s Disease.
- Moderate Alzheimer’s Disease.
- Severe Alzheimer’s Disease.
The table below lists the symptoms of mild, moderate, and severe Alzheimer’s Disease.
| Symptoms Of Mild Alzheimer’s Disease | Symptoms Of Moderate Alzheimer’s Disease | Symptoms Of Severe Alzheimer’s Disease |
| Memory loss. | Memory loss and confusion. | Losing the ability to communicate. |
| Changes in mood and personality. | Unable to recognize family and friends. | Increased weight loss. |
| Losing or misplacing things in unusual places. | Difficulty with writing or reading. | Losing control of one’s bowel and bladder. |
| Constantly repeating what one has said. | Unable to think logically and organize thoughts. | Seizures. |
| Wandering off and getting lost. | Difficulty with performing simple tasks such as getting dressed. | Sleeping more than usual. |
| Anxiety and aggression. | Paranoia and hallucinations. | Unusual sound making such as moaning or grunting. |
Alzheimer’s Disease And The Caudate Nucleus
In 2013 a study was conducted which resulted in researchers finding a link between Alzheimer’s Disease and the Cordate Nucleus. In the study, researchers compared MRI images of patients with Alzheimer’s Disease to those of individuals who did not have the disease.
After the comparison, researchers identified a reduction in the caudate volume of patients suffering from this disease.
2. Parkinson’s Disease
Parkinson’s Disease is a progressive neurodegenerative disorder characterized by uncontrollable movements such as shaking, stiffness, and trouble balancing and coordinating.
| Common Symptoms Of Parkinson’s Disease | Less Common Symptoms Of Parkinson’s Disease |
| Having tremors in one’s hands, arms, legs, or head. | Struggling to speak, chew and swallow. |
| Severe muscle stiffness and contractions for long periods of time. | Depression. |
| Falling as a result of impaired balance and coordination. | Problems with urinating and constipation. |
| Movement at a slow pace. | Dementia. |
Parkinson’s Disease And The Caudate Nucleus/Basal Ganglia
Parkinson’s Disease usually develops when nerve cells in the Basal Ganglia are impaired or die. As mentioned above, the Caudate Nucleus forms part of this important structure which is responsible for controlling movements.
The nerve cells/neurons in the Basal Ganglia produce the chemical dopamine. However, when these neurons die or get damaged, they cannot produce this chemical, which results in movement problems associated with Parkinson's Disease. Therefore, this disease depletes dopaminergic neurons found in the nigrostriatal tract.
- Nigrostriatal tract. The nigrostriatal tract is a dopamine pathway that is strongly connected to the Caudate Nucleus’s head.
3. Huntington’s Disease
Huntington’s Disease is a rare and inherited condition that results in the degeneration/breakdown of nerve cells in the brain, causing parts of the brain to stop working overtime.
With Huntington’s Disease, researchers found that a genetic mutation occurs in the HTT gene, which causes the production of the Htt protein. The production of this mutated protein is extremely dangerous as the Htt protein negatively interacts with more than 100 other proteins and is toxic to several cell types in the brain.
This disease is known to cause movement, cognitive and psychiatric disorders. Each disorder has its own unique symptoms. The table below lists the symptoms associated with these three disorders.
| The Symptoms Associated With Movement Disorders | The Symptoms Associated With Cognitive Disorders | The Symptoms Associated With Psychiatric Disorders |
| Muscle contractions and rigidity. | Lacking impulse control which results in one acting without thinking. | Irritability, apathy, and sadness are felt more strongly. |
| Involuntary movements. | Inability to organize and prioritize tasks. | Difficulty sleeping. |
| Balance, posture, and the manner of walking are impaired. | The processing of thoughts or finding words is slow. | Lack of energy and fatigue. |
| Struggling to swallow and speak. | Unable to learn new information. | Depression that leads to frequent thoughts about suicide. |
| Eye movement is slow and unusual. | Unaware of one’s behaviors and abilities. | Constant changes in one’s mood and personality. |
Huntington’s Disease And The Caudate Nucleus
In the early stages of Huntington’s disease, researchers identified that damages were most evident in what is known as the Striatum, which is composed of the Caudate Nucleus and the Putamen. These damages often result in Striatum atrophy (degeneration), Caudate Nucleus atrophy, and cause changes in the binding potential of dopamine receptors in the Caudate Nucleus.
4. Attention-Deficit Hyperactivity Disorder
Attention-Deficit Hyperactivity Disorder, also known as ADHD, is a common neurodevelopmental disorder that affects one’s behavior. There are three ways ADHD presents itself:
- Predominantly Inattentive Presentation.
- Predominantly Hyperactive-Impulsive Presentation.
- Combined Presentation.
The symptoms of this disorder are different as it depends on the way ADHD presents itself. The table below displays the symptoms associated with each of these ways.
| The Symptoms Associated With Predominantly Inattentive Presentation | The Symptoms Associated With Predominantly Hyperactive-Impulsive Presentation | The Symptoms Associated With Combined Presentation |
| Difficulty with organizing and finishing tasks. | Fidgeting. | The symptoms of Combined Presentation combine the symptoms of the other two discussed. |
| Having trouble paying attention. | Talking a lot. | |
| Unable to follow instructions. | Unable to sit still. | |
| Easily distracted. | Lack of impulse control. | |
| Forgets things easily. | Restlessness. |
ADHD And The Caudate Nucleus/Basal Ganglia
Researchers found that individuals with Attention-Deficit Hyperactivity Disorder had abnormally low levels of neurotransmitters transmitting dopamine and noradrenaline between the prefrontal cortical area and the Basal Ganglia. With the Caudate Nucleus being part of the Basal Ganglia, this structure receives low dopamine levels, resulting in the various symptoms discussed above.
Conclusion
With all that said, the Caudate Nucleus is, without a doubt, a very important structure within the brain. This C-shaped structure that forms part of the Basal Ganglia might be small and not as well-known as the other parts of the brain, but it sure is involved in many essential motor and cognitive functions.
Furthermore, this small structure is also linked to many disorders. These disorders are either caused by the dysfunction of the Caudate Nucleus or are responsible for damages to this structure.
References
https://www.healthline.com/human-body-maps/caudate-nucleus
https://en.wikipedia.org/wiki/Caudate_nucleus
https://www.nia.nih.gov/health/what-alzheimers-disease
https://www.nhs.uk/conditions/attention-deficit-hyperactivity-disorder-adhd/
