The frontal lobe is possibly the brain area that most distinguishes humans from the rest of the animals. For this reason, it has aroused special interest in the researchers, who have carried out multiple studies on their functions and operating mechanism.
The human frontal lobe is widely related to functions as important as language, control of motor actions and executive functions, so that, if injured, the person can suffer serious problems that we will also discuss in this article.
Neuroanatomy of the frontal lobe
Before explaining the functions of the frontal lobe, its location and anatomy will be described.
The brain is composed of cortical areas and subcortical structures, I will start with the cortical areas since the frontal lobe is one of them.
The cerebral cortex is divided into lobes, separated by grooves, the most recognized being the frontal, parietal, temporal and occipital, although some authors postulate that there is also the limbic lobe (Redolar, 2014).
The cortex is divided into two hemispheres, the right and the left, so that the lobes are present symmetrically in both hemispheres, with a right frontal lobe and a left lobe, a right and left parietal lobe, and so on..
The cerebral hemispheres are divided by the interhemispheric fissure while the lobes are separated by different grooves.
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The frontal lobe reaches from the most anterior part of the brain to the fissure of Rolando (or central fissure) where the parietal lobe begins and, on the sides, to the Sylvian fissure (or lateral fissure) that separates it from the temporal lobe.
Regarding the anatomy of the human frontal lobe, it can be said that it is very voluminous and has a pyramid shape. It can be divided into precentral and prefrontal cortex:
- The precentral cortex is composed of the primary motor cortex (area 4 of Brodmann), the premotor cortex and the supplementary motor cortex (area 6 of brodmann). This zone is basically motor and controls the phasic movements of the body (programming and initiation of movement) as well as the movements necessary to produce language and posture and body orientation.
- The prefrontal cortex , is the zone of association, consists of dorsolateral, ventrolateral and orbitofrontal cortex, and its functions are related to the executive system, such as the control and management of executive functions.
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The frontal lobe, and especially the prefrontal cortex, is the cortical area most widely connected to the rest of the brain. The main connections are the following:
- Cortico-cortical frontal connections. Receive and send information to the other lobes. The most important are the frontotemporal connections, which are related to the audioverbal activity and frontoparietals, related to the control and regulation of cutaneous-kinesthetic sensitivity and pain.
- Cortico-subcortical frontal connections .
- Fronto-thalamic connections.
- Centrallateral thalamic nuclei that connect with the precentral cortex.
- Dorsomedial thalamic nucleus that connects with the prefrontal cortex, related in some way to memory.
- Anterior ventral thalamic nucleus that connects with the limbic frontal cortex (cingulate area).
- Fronto-limbic connections. They facilitate emotional and affective regulation through neuroendocrine and neurochemical secretions.
- Fronto-basal circuits. In these circuits some sections of the frontal lobe are connected with the striated, the pale globe and the thalamus:
- Motor circuit, related to the control of movements.
- Oculomotor circuit, related to the association between our movements and the position of objects identified through sight.
- Dorsolateral prefrontal circuit, related to executive functions.
- Cingulate prefrontal circuit, related to emotional responses.
- Fronto-thalamic connections.
A rough way could be said that the frontal lobe receives inputs from the areas responsible for the sensory processing of information and sends outputs to the areas responsible for giving a response, especially motor.
The prefrontal cortex
The prefrontal cortex is the last area to develop in the frontal lobe and brain in general. This area is especially important because it fulfills functions without which we would not be effective in our day-to-day activities, such as planning and organizing future behaviors.
It has a pyramid shape, like the frontal lobe, and has an internal face, an external and an internal.
Regarding the connections it establishes with the rest of the structures, there are three main circuits:
- Dorsolateral prefrontal circuit. It goes to the dorso-lateral zone of the caudate nucleus. From here it connects with the pale back-medial globe and with the black substance. They project the dorso-medial and ventral-anterior Thalamic Nuclei, and from there they return to the prefrontal cortex.
- Orbitofrontal circuit. It projects to the ventromedial caudate nucleus, then to the pale globe and the ventro-medial black substance, from there it passes to the ventral-anterior and dorsal-medial thalamic nuclei and finally returns to the prefrontal cortex.
- Previous cingulate circuit. It projects to the ventral striatum, this has connections with the pale globe, the ventral tegmental area, the habenula, the hypothalamus and the amygdala. Finally it returns to the prefrontal cortex.
The functions of structuring, organizing and planning behavior are attributed to this area. The patient suffers the following failures if this area is injured:
- Failures in selective capacity.
- Failures in sustained activity.
- Deficits in the associative capacity or in the formation of concepts.
- Deficits in planning capacity.
Frontal lobe functions
The frontal lobe fulfills multiple functions that can be summarized in:
- Executive functions:
- Virtual simulation of the behavior to be carried out through experiences and previous and vicarious learning.
- Setting a goal and the steps that must be followed to complete it.
- Planning, coordination and implementation of the necessary behaviors to achieve the objective.
- Maintenance of the objectives throughout the process until reaching the goal. Here the working memory and the sustained attention are involved.
- Inhibition of other stimuli that have nothing to do with the goal and that may interfere with them.
- Coordination of all the necessary systems to perform the necessary actions, such as sensory, cognitive and behavioral.
- Analysis of the results obtained and, if necessary, modification of the behavior patterns based on these results.
- Social functions:
- Inference of the intentions and thoughts of others. This ability is called theory of mind.
- Reflection about our knowledge and interests and ability to communicate them.
- Emotional functions:
- Control of reinforcing stimuli to motivate us to perform the cognitive processes and behaviors that we should perform.
- Regulation of impulses.
- Consciousness of emotions.
- Motor functions:
- Sequencing, coordination and execution of motor behaviors.
- Linguistic functions:
- Ability to understand the language of others and produce our own.
Next, the executive functions will be described in greater depth because of their great importance in humans.
Executive functions could be defined as the last step in the control, regulation and direction of human behavior. This concept arises for the first time from the hand of AR Luria in 1966 in his book Higher Cortical Function in Man (cited in León-Carrión & Barroso, 1997).
Lezak popularized this term in American psychology. This author highlights the difference between executive and cognitive functions, stating that, although cognitive functions suffer damage if the executive functions function correctly, the person will continue to be independent, constructively self-sufficient and productive (cited in León-Carrión & Barroso, 1997).
The executive functions are made up of four components:
1- Formulation of goals . It is the process by which needs are determined, what is wanted and what is capable of achieving what is wanted. If a person has this function altered, he can not think about what he should do and presents difficulties in starting activities.
These alterations can occur without the need of brain damage, simply with a poor organization in the prefrontal lobe.
2- Planning It is responsible for determining and organizing the necessary steps to carry out an intention.
This process requires certain capacities such as: conceptualizing changes in present circumstances, developing oneself in the environment, seeing the environment objectively, capable of conceiving alternatives, carrying out elections and developing a structure to carry out the plan.
3- Implementation of plans. It is interpreted as the action of initiating, maintaining, changing and for sequences of complex behaviors in an integral and orderly manner.
4- Effective execution. It is the assessment based on the objectives and resources used to achieve those objectives.
The teaching system is very important for the correct configuration of executive functions, since these functions begin to develop in childhood, from the first year of life, and do not mature until puberty or even later.
The executive functions are mainly related to the prefrontal cortex, but some studies performed with PET (positron emission tomography) indicate that, when the activity becomes routine, another part of the brain takes over the activity to “free” the prefrontal cortex and that it can take care of performing other functions.
Executive performance evaluation
The most used techniques for the evaluation of the executive system are:
- Wisconsin Card Sorting Test. Test in which the patient has to classify a series of cards in several ways, using a different category each time. Failures in this test would imply problems in the formation of concepts that could be due to injuries in the left frontal lobe.
- The tower of Hanoi-Seville. This test is used to examine complex problem-solving skills.
- Labyrinth tests. These tests provide data on the highest levels of brain functioning that require planning and foresight.
- Construction toys. These are unstructured tests and are used to evaluate executive functions.
Dysfunctions of the frontal lobe
The frontal lobe can be damaged as a result of trauma, heart attacks, tumors, infections or the development of some disorders such as neurodegenerative or developmental disorders.
The consequences of frontal lobe damage will depend on the damaged area and the extent of the injury. The syndrome, due to damage to the frontal lobe, better known is the prefrontal syndrome that will be described below.
The prefrontal syndrome
The first well-documented description of a case of this syndrome was made by Harlow (1868) about the case of Phineas Gage, over time this case has continued to be studied and today is one of the best known in the field of psychology (cited in León-Carrión & Barroso, 1997).
Phineas was working on the tracks of a train when he had an accident while compacting gunpowder with an iron bar.
It seems that a spark came to the gunpowder and it exploded by throwing the iron bar directly at his head. Phineas suffered a lesion in the left frontal lobe (specifically in the medial orbital region) but he was still alive, although he still had sequels.
The most significant changes due to the injury suffered were increased impulses, inability to control and difficulties to plan and organize.
People with the injured prefrontal cortex have changes in personality, motor skills, attention, language, memory and executive functions.
According to Ardila (cited in León-Carrión & Barroso, 1997) there are two ways to describe the changes in personality caused by this syndrome:
- Changes in activation for the action. Patients tend to feel apathy and disinterest, therefore, they do everything with reluctance and are not very proactive.
- Changes in the type of response. The patient’s response is not adaptive, it does not correspond to the stimulus presented to him. For example, they can take an exam and choose the clothes they are going to wear for too long instead of studying.
Changes in Motricity
Among the changes in motor skills we can find:
- Neonatal reflexes. It seems as if the patients involucionaran and returned to have the reflexes that have the babies and they are lost with the development. The most usual are:
- Reflection of Babinski. Dorsal tonic extension of the big toe.
- Prehension reflex. Close the palm of your hand when something touches it.
- Reflection of suction.
- Palmomentonian reflex. Touching the palm of the hand triggers chin movements.
- Repeat the examiner’s actions.
- They react exaggeratedly to stimuli.
- Disorganization of behavior.
- Repeat the same movement again and again.
Changes in Attention
The main changes are in the orientation response, patients have deficits to orient themselves to the stimuli they should at home and when following the instructions of the examiner.
The most characteristic is:
- Transcortical motor aphasia. The language is very limited and it is reduced to short phrases.
- Subvocal language. Changes in the speech device, probably due to aphasia, so that the person pronounces strangely.
- Commission of naming errors, how to persevere and respond before fragments of the stimulus and not the stimulus in global.
- They respond better to visual than verbal stimuli because they have poor control of behavior through language.
- They can not maintain a central topic of conversation.
- Lack of connection elements to give shapes and make the logical language.
- Concretism. They give concrete information without putting it in context, which can make it difficult for the interlocutor to understand.
Changes in Memory
The frontal lobes play an important role in memory, especially in short-term memory. Patients with lesions in the frontal lobe present problems in storage and memory retention. The most frequent alterations are:
- Temporal organization of memory. Patients have problems ordering events over time.
- Amnesias, especially for injuries produced in the orbital area.
Changes in executive functions
The executive functions are the most affected in patients with frontal lesions, given that a complex elaboration and the integration and coordination of several components are necessary for its correct performance.
People with a frontal syndrome are unable to form a goal, plan, carry out actions in an orderly manner and analyze the results obtained. These deficits prevent them from leading a normal life as they interfere with their work/school, family, social tasks …
Although the symptoms described are the most common, their characteristics are not universal and will depend on both patient variables (age, premorbid performance …), and injury (specific location, a magnitude …) and the course of the syndrome.
The category of frontal syndromes is very broad and encompasses another series of syndromes that differ according to the injured area.
Cummings (1985), describes three syndromes (cited in León-Carrión & Barroso, 1997):
- Orbitofrontal syndrome (or disinhibition). It is characterized by disinhibition, impulsiveness, emotional lability, poor judgment, and distraction.
- Frontal (or apathetic) convexity syndrome. It is characterized by apathy, indifference, psychomotor retardation, loss of momentum, abstraction and poor categorization.
- Frontal (or akinetic frontal lobe) syndrome. It is characterized by a lack of spontaneous gestures and movements, weakness and loss of sensation in the extremities.
Imbriano (1983) adds two more syndromes to the classification elaborated by Cummings (cited in León-Carrión & Barroso, 1997):