1. What Are the Executive Functions?

Executive functions are higher-level cognitive skills and processes that are necessary for the control and coordination of other cognitive abilities and behaviors [1]. 

Executive functions can be divided into organizational and regulatory executive functions.

1.1. What Are Organizational Executive Functions?

Organizational executive functions involve the collection and structuring of information for evaluation. These functions include the following processes:

• Attention
• Planning
• Sequencing
• Problem-solving
• Working memory
• Cognitive flexibility
• Abstract thinking
• Rule Acquisition
• Selecting of relevant sensory information

1.1.1.  What Is Attention?

Attention is the capacity to choose between paying attention to something or ignoring it.

1.1.2. What Is Planning?

Planning is the capacity to think ahead to achieve the desired goal.

1.1.3. What Is Sequencing

Sequencing is the process of analyzing (reasoning) available information to reach conclusions.

1.1.4. What Is Problem-solving?

Problem-solving relies on using ad hoc methods to find solutions to problems.

1.1.5. What Is Working memory?

Working memory is a temporary storage of a small amount of information ready for immediate mental use.

1.1.6. What Is Cognitive flexibility?

Cognitive flexibility is the mental process of switching between different tasks and resulting behaviors.

1.1.7. What Is Abstract thinking?

Abstract thinking is the capacity to understand complex concepts without necessarily requiring physical perceptions.

1.1.8. What Is Rule Acquisition?

Rule Acquisition is the process of acquiring new rules that are based on reasoning, problem-solving, and conclusions.

1.1.9. What Is Selection of relevant sensory information?

The selection of relevant sensory information is the process of choosing the appropriate perceived information.

1.2. What Are Regulatory Executive Functions?

Regulatory executive functions are involved in the evaluation of the information that was collected and structured by the organization executive functions to regulate responses to the environment.

These functions include the following processes:

• Action initiation
• Self-control
• Emotional regulation
• Monitoring internal and external stimuli
• Initiating and inhibiting context-specific behavior
• Moral reasoning
• Decision-making

1.2.1. Action Initiation

Action initiation is the first step in translating thoughts into behaviors (actions).

1.2.2. Self-control

Self-control is an inhibitory control of attention, thoughts, behaviors, or emotions associated with a strong internal predisposition. 

1.2.3. Emotional regulation

Emotional regulation is the management of our own emotions in response to stimuli.

1.2.4. Monitoring internal and external stimuli

This process is associated with the management of internal stimuli such as thoughts or emotions, and external stimuli such as sensory information.

1.2.5. Initiating and inhibiting context-specific behavior

This process is associated with self-monitoring and evaluating a specific behavior in response to a specific context.

1.2.6. Moral reasoning

Moral reasoning is the logical process that allows the distinction between right and wrong.

1.2.7. Decision-making

Decision-making is the process of selecting an action or behavior from existing alternative choices.

2- What Are the Conditions that Can Cause Executive Functions Issues?

Executive functions issues can be due to a variety of neurological, psychiatric, and developmental disorders. The following are some of the disorders associated with executive functions deficits:

• Traumatic brain injury
• Frontotemporal dementia
• Cerebrovascular disease
• Obsessive-compulsive disorder
• Tourette’s syndrome
• Depression
• Schizophrenia
• Attention-deficit/hyperactivity disorder
• Autism

2.1. Traumatic brain injury

Injury to the prefrontal regions of the frontal lobes can to deficits in executive functions.

2.2. Frontotemporal dementia

Frontotemporal dementia is a neurodegenerative disease affecting the frontal and temporal parts of the brain causing cognitive disorders [2].

The cognitive disorders manifest with symptoms such as:

• Distance from family
• Vulgar speech
• Screaming
• Incapacity to control emotions, behavior, and temperament
• Obsessive and compulsive tendency to buy things

Frontotemporal Dementia is due to mutations in the gene MAPT that encodes for a protein known as TAU.

Mutations in the gene MAPT results in increased production of TAU and its accumulation in neurons and glia leading to their death.

2.3. Cerebrovascular disease

Cardiovascular diseases are diseases that affect the normal function of the heart and blood vessel circulation.

The most common cardiovascular diseases include coronary heart disease, stroke, and peripheral arterial disease.

Cardiovascular diseases can result in the reduction of blood supply to prefrontal regions of the frontal lobes leading to deficits in executive functions.

2.4. Obsessive-compulsive disorder (OCD)

Obsessive-compulsive disorder (OCD) is a common mental health condition characterized by unwanted and repeated thoughts and compulsive behavior [3].

OCD can be caused by genetics, drugs such as second-generation antipsychotics or olanzapine, or autoimmunity.

2.5. Tourette’s syndrome

Tourette syndrome is a neurological disease that affects certain parts of the brain (frontal subcortical circuits) responsible for voluntary movements [4].

It is characterized by both vocal and motor chronic tics that are sudden and repetitive such as blinking, clearing throat, grunting, or facial movements [5].

The genetic causes of Tourette’s Syndrome are unknown; however, some cases are associated with mutations in genes such as SLITRK1, CNTNAP2, and HDC.

SLITRK1 is a protein found in the membrane of neurons where it is involved in the regulation of synapses.

CNTNAP2 is a protein found in the membrane of the neurons where it plays a role in axons, while HDC is an enzyme involved in the function of the neurotransmitter histidine.

2.6. Depression

Major Depressive Disorder (MDD) or depression is a debilitating mental disorder characterized by a depressed mood (low mood), low self-esteem, and loss of interest in previously enjoyable activities.

Major depression can be due to genetic factors (family history) or health issues.

It was estimated that around 7.1% of US adults had a least one major depression in their life [6]. Major depression is more prevalent in women (8.7%) than men (5.3%).

2.7. Schizophrenia

Schizophrenia is a complex and severe mental health disorder that is classified as a type of psychosis. It is characterized by significant alterations in thoughts, perception, mood, and behaviors.

The causes are not well known; however, it was suggested that the causes may be associated with a cognitive decline due to alterations in brain development, particularly of the cerebral cortex [7].

It is estimated that 20 million people have schizophrenia worldwide with a predominance in individuals aged between 16 and 30 years [8].

Although schizophrenia is classified as a type of psychosis, this classification has been challenged due to the long and progressive cognitive decline before the onset of psychosis (Dementia praecox) and which suggests a more neurobiological basis.

2.8. Attention-deficit/hyperactivity disorder (ADHD)

ADHD is a neurodevelopmental condition that results in behavioral impairment leading to symptoms such as lack of attention, hyperactivity, and impulsivity [9]. It can be caused by genetic, environmental, or societal factors.

2.9. Autism

Autism is a neurodevelopmental condition characterized by behavioral impairment leading to difficulties in communication and social interactions [10].

It is caused by complex genetic factors but also by malnutrition or inflammation during pregnancy. Other potential factors involve environmental factors such as air pollution (e.g., heavy metals)

Conclusion

Executive functions are controlled by the prefrontal regions of the frontal lobes and are essential in our everyday life as they allow us to collect, structure, and evaluate information, and make behavioral decisions.

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