Executive functions can be defined as the ability to plan and coordinate purposeful action in the face of alternatives, to monitor and update action as necessary, and to remove distractions by focusing on the task at hand.
It regulates our emotions and our behaviour and allows the individual to adapt to sudden changes in the environment. These functions are controlled by the frontal lobes.
The main executive functions
- Organization and planning. Planning is the ability to organize mental activity around a goal, taking into account the steps necessary to achieve that goal. People with a frontal lesion often have difficulty planning.
- Mental flexibility. It is the ability to modify one’s cognitive scheme in response to environmental stimuli. The regions of the brain associated with flexibility are mainly located in the left hemisphere, notably Broca’s area (language), the parietal cortex (spatial orientation) and the prefrontal cortex (working memory).
- Abstraction. It is the ability to think about general situations or elements, symbolically. The Wisconsin card sorting test assesses mental flexibility, but also provides information on reasoning skills.
- Judgment. Judgment often involves situations without a moral aspect. It may concern the comparison of the best choice between two options, or the assessment of the risk in a particular situation. Among the tests to assess decision-making is the Iowa Gambling Task.
- Self-monitoring. It consists of modulating or inhibiting one’s behaviour and actions according to the context and external requirements. Generally, a lack of inhibition translates into impulsivity. The inhibition involves several regions of the brain, located mainly in the frontal lobe. Inhibition deficits are observed in several psychiatric disorders.
What role do executive functions play?
Executive functions allow a person to adapt to new situations (adaptability) and to solve more or less complex problems.
To solve these problems, the subject must identify the steps necessary to implement a strategy, taking into account environmental factors.
The executive functions also bring into play mechanisms which make it possible to eliminate information which is useless. (For example, “erasing” from your head a telephone number that you have just dialed).
Executive functions therefore include action inhibition, memory, attention, flexibility, planning and problem-solving.
Although there is no consensus on a definition, it is widely accepted that the activities to which the term refers are essential to day-to-day functioning.
People who have difficulty inhibiting themselves, remembering things, planning, problem-solving, or mental flexibility will show significant deficits in social and occupational functioning.
What brain structures are involved?
The frontal and parietal cortices, as well as certain subcortical structures of the limbic system (amygdala, hippocampus) are involved in executive functions.
Neuroimaging examinations, which can detect abnormalities in these regions, are often useful when a patient presents with behavioural problems (e.g. aggression, apathy).
Evaluation of executive functions
The evaluation of the executive functions is done when a patient presents behavioral disorders, in particular after a cranial traumatism or a dementia (in particular a frontotemporal dementia ).
Behavioural disorders are as follows: apathy, lack of initiative, indifference, withdrawal into oneself…or on the contrary, disinhibition with foul language, euphoria, familiarity, inappropriate attitudes and breaking instructions (e.g. he undresses, behaves badly at the table, urinates in public…).
These disorders can interfere with memory and have a negative impact on activities of daily living.
Another reason that leads the doctor to examine executive functions is that the person may have difficulty adapting to everyday situations. In fact, executive functioning disorders can go unnoticed when the elderly person performs routine tasks (eg washing, cleaning, preparing to eat, driving a car, etc.)
The evaluation of executive functions is done using neuropsychological tests. Here are some of them described below:
It assesses the patient’s inhibition capacity (ability to eliminate irrelevant information). The patient must name the colour of the ink with which a different colour name is written (this is called an interference test). He must therefore disregard the word.
Example: the patient must say “green”, “red”, “yellow”, then “blue” when he sees the image below:
The Frontal Evaluation Battery
This test includes six tests: test of similarities, fluidity, instructions etc.
For example, the examiner shows the patient an orange and an apple and says: how are they similar? (this is the similarity test).
The trail making test
The trail making task is a test often used in the assessment of cognitive functions. This test requires good visual and spatial skills, rapid motor performance, and of course correct reading of numbers and letters. First, the subject must connect numbers in ascending order as quickly as possible, and then connect numbers and letters alternately
Le Wisconsin Card Sorting Test
It is essentially a test of deduction. The subject must find a common point between 48 cards presented by the examiner and 4 other cards which differ in colour and shape (rounds, squares, triangles, etc.). These 4 cards can be for example a green triangle, two red squares, three black crosses and four blue circles. The examiner does not give instructions on how the patient should organize his cards. It tells him only by yes or no if the criterion (for example the shape, the colour) chosen is the right one.
The main measure of this task is the number of times the patient makes the same error (e.g. the patient continues to classify the cards by colour even though the examiner has clarified to the patient that the color is not the selection criterion). The examiner will see if the patient can cancel out a false answer that has become routine to him.
The tower of London
The Tower of London a test of planning skills, with 12 problems of increasing difficulty.
Different behavioural questionnaires can be submitted to patients who present with a cognitive function disorder. These are for example the Frontal Dysfunction Scale or the Behavioral Dysexecutive Syndrome Inventory.