He Frontal lobe Possibly the brain area that most distinguishes humans from the rest of the animals. It has therefore attracted particular interest in researchers, who have carried out numerous studies on their functions and their mechanism of operation.
The human frontal lobe is closely related to such important functions as language, control of motor actions and executive functions, so that if injured, the person can suffer serious problems which we will also discuss in this article.
Neuroanatomy of the frontal lobe
Location
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 begin with the cortical areas since the frontal lobe is one of them.
The cerebral cortex is divided into lobes, separated by furrows, the most recognized being frontal, parietal, temporary and the occipital , Although some authors postulate that there is also the Limbic lobe (Redolar, 2014).
The crust is divided in turn into Two hemispheres , Right and left, so that the lobes are symmetrically present in both hemispheres, with one right and one left frontal lobe, one right and left parietal lobe, and so on.
The cerebral hemispheres are divided by interhemispheric fissure whereas the lobes are separated by different furrows.
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The frontal lobe extends from the most anterior part of the brain to the Fissure of Roland (Or central fissure) where it begins The parietal lobe And, on the sides, to the fissure of Silvio (or lateral fissure) that separates the temporal lobe.
As for the anatomy of the human frontal lobe, it can be said that it is very bulky 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 (area 6 of brodmann). This area 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 association zone, is composed of dorsolateral cortex, ventrolateral and orbitofrontal, 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 as follows:
- Cortical-cortical frontal connections . Receives and sends information to the rest of lobes. The most important are the frontotemporal connections, which are related to the audioverbal and frontoparietal activity, related to the control and regulation of cutaneo-kinesthetic sensitivity and pain.
- Cortical-subcortical front connections .
- Fronto-thalamic connections.
- Centrolateral thalamic nuclei connecting to the precentral cortex.
- Dorsomedial thalamic nucleus connecting to the prefrontal cortex, related in some way to memory.
- Anterior ventral thalamic nucleus connecting to the frontal limbic 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 striatum, the pale balloon and the thalamus:
- Motor circuit, related to the control of movements.
- Oculomotor circuit, related to the association between our movements and the position of the objects identified through the view.
- Dorsolateral prefrontal circuit, related to executive functions.
- Cingulate prefrontal circuit related to emotional responses.
- Fronto-thalamic connections.
In a gross way one could say that the frontal lobe receives Inputs Of areas responsible for sensory processing of information and sends Outputs To the areas in charge of giving a response, especially motor.
The prefrontal cortex
The prefrontal cortex is the last developing zone of the frontal lobe and the brain in general. This area is especially important because it fulfills functions without which we would not be effective in our daily life, such as planning and organizing future behaviors.
It has a pyramid shape, just like the frontal lobe, and has an inner, an outer and an inner face.
As for the connections that it establishes with the rest of structures, there are three main circuits:
- Dorsolateral prefrontal circuit . It goes to the dorsolateral side of the Caudate nucleus . From here it connects with the pale dorsal-medial globe and with the Black substance . These project to the dorsal-medial and ventral-anterior thalamic nuclei, and from there they return to the prefrontal cortex.
- Orbitofrontal circuit . It projects the ventromedial caudate nucleus, then the pale balloon and the ventro-medial black substance, from there it passes to the thalamic nuclei ventral-anterior and dorso-medial and finally returns to the prefrontal cortex.
- Anterior cingulate circuit . It projects the ventral striatum, which has connections to the pale balloon, the ventral tegmental area, the habenula, the Hypothalamus And the amygdala. Finally it returns to the prefrontal cortex.
This area is attributed the functions of structuring, organizing and planning behavior. The patient suffers the following faults if this area is injured:
- Failures in selective capacity.
- Failures in sustained activity.
- Deficits in associative capacity or in the formation of concepts.
- Deficits in planning capacity.
Functions of the frontal lobe
The frontal lobe fulfills multiple functions that can be summarized in:
- Executive functions:
- Virtual simulation of behavior to be carried out through previous experiences and vicarious learning.
- Setting a goal and the steps that must be followed to complete it.
- Planning, coordination and implementation of the behaviors necessary to achieve the objective.
- Maintain objectives throughout the process until reaching the goal. Work memory and sustained attention are involved here.
- Inhibition of the rest of stimuli that do not have to do with the goal and that can interfere with them.
- Coordination of all the systems needed to perform the necessary actions, such as sensory, cognitive and behavioral.
- Analysis of the results obtained and, if necessary, modification of behavior patterns based on these results.
- Social functions:
- Inference of the intentions and thought of others. This capacity is called Theory of mind .
- Reflection on our knowledge and interests and ability to communicate.
- Emotional functions:
- Control of reinforcing stimuli to motivate us to perform the behaviors and cognitive processes that we have to perform.
- Regulation of impulses.
- Awareness of emotions.
- Motor functions:
- Sequencing, coordination and execution of motor behaviors.
- Linguistic functions:
- Ability to understand the language of others and produce our own.
The executive functions will be described in greater depth because of their great importance in humans.
Executive functions
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 A.R. Luria In 1966 in his book Higher Cortical Function in Man (quoted in León-Carrión & Barroso, 1997).
Lezak popularized this term in American psychology. This author highlights the difference between executive and Cognitive , Stating that, even if cognitive functions are damaged if executive functions function correctly, the person will continue to be independent, constructively self-sufficient and productive (quoted in León-Carrión & Barroso, 1997).
Executive functions consist of four components:
1- Formulation of goals . It is the process by which the needs are determined, what is wanted and what is capable of achieving what one wants. If a person has altered this function can not think what to do and presents difficulties in starting activities.
These alterations may occur without the need for brain damage, simply with poor organization in the prefrontal lobe.
2- Planning. It is responsible for determining and organizing the steps necessary to carry out an intention.
This process requires determined capacities such as: conceptualizing the changes in the present circumstances, seeing itself developed in the environment, seeing the environment objectively, able to conceive alternatives, carry out elections and develop 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 way.
4- Effective execution. It is the assessment based on the objectives and resources used to achieve those objectives. objectives .
The teaching system is very important for the correct configuration of the 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 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 other functions.
Evaluation of the executive functioning
The techniques most used 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 lesions in the left frontal lobe.
- The tower of Hanoi-Seville . This test is used to examine complex problem-solving skills.
- Maze Testing . These tests provide data on the highest levels of brain functioning that require planning and forecasting.
- Construction toys . These are poorly structured tests and are used to evaluate executive functions.
Frontal lobe dysfunctions
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 magnitude of the injury. The syndrome, due to frontal lobe damage, is best known as the prefrontal syndrome described below.
The prefrontal syndrome
The first well-documented description of a case of this syndrome was by Harlow (1868) on The case of Phineas Gage , This case has continued to be studied over the years and today it 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 rod.
It seems that a spark came to the gunpowder and exploded throwing the iron bar directly to his head. Phineas suffered a lesion in the left frontal lobe (specifically in the medial orbital region) but remained alive, although he had sequelae.
The most significant changes due to the injury he suffered were increased impulses, inability to control, and difficulties in planning and organizing.
People with the injured prefrontal cortex present changes in the personality , In the motor, in the attention, in the language, in the memory And executive functions.
Personality changes
According to Ardila (cited in León-Carrión & Barroso, 1997) there are two ways to describe the personality changes caused by this syndrome:
- Changes in activation for action. Patients often feel apathetic and disinterest, therefore everything is done with reluctance and are not very proactive.
- Changes in response type. The patient's response is not adaptive, it does not correspond to the stimulus that is presented to him. For example, they can take an exam and get to choose the clothes they are going to wear for too long instead of studying.
Changes in Motor
Among the changes in motor skills we can find:
- Neonatal reflexes. It seems as if the patients involucionaran and have the reflexes that have the babies and are lost with the development. The most common are:
- Babinski Reflection . Dorsal tonic extension of the big toe.
- Reflection of grip. Close the palm of your hand when something touches you.
- Suction reflex.
- Reflex palmomentoniano. Touching the palm of the hand triggers movements on the chin.
- Repeat the examiner's actions.
- They react exaggeratedly to the stimuli.
- Disorganization of behavior.
- Repeat the same movement over and over again.
Changes in Care
The main changes are given in the orientation response, patients have deficits to orient themselves to the stimuli that they should at home and following the instructions of the examiner.
Language Changes
The most characteristic are:
- Transcortical motor aphasia. The language is very limited and is reduced to short phrases.
- Subvocal language. Changes in the speech apparatus, probably due to aphasia, so the person pronounces strangely.
- Commission of denomination 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 shape and make logical language.
- Concretism. They give concrete information without putting it into context, which may hinder the understanding of its interlocutor.
Changes in Memory
The frontal lobes play an important role in memory, especially in short-term memory. Patients with frontal lobe lesions have problems with memory storage and retention. The most frequent alterations are:
- Temporary organization of memory. Patients have problems ordering events over time.
- Amnesias , Especially for injuries produced in the orbital zone.
Changes in executive functions
The executive functions are the most affected in the patients with frontal injuries since for their correct realization it is necessary a complex elaboration and the integration and coordination of several components.
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 carrying on a normal life because they interfere with their work tasks / school, family, social...
Although the symptoms described are the most common, their characteristics are not universal and will depend on both the patient's variables (age, premorbid execution...), and the lesion (specific location, magnitude...) and the course of the syndrome.
Typical syndromes
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, impulsivity, Emotional lability , Poor judgment and distractibility.
- Frontal convexity syndrome (Or apathetic). It is characterized by apathy , Indifference, psychomotor retardation, loss of momentum, abstraction and poor categorization.
- Middle frontal syndrome (Or akinetic of the frontal lobe). 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):
- Polar Syndrome. Produced by injuries in the orbital zone. It is characterized by alterations of intellectual capacity, temporo-spatial disorientation and lack of self-control.
- Esplenial Syndrome. Produced by left medial lesions. Characterized by alterations of the affective facial expressions and affective indifference, disorders of the thought and alterations of the language.
References
- Carmona, S., & Moreno, A. (2014). Executive control, decision making, reasoning and problem solving. In D. Redolar, Cognitive Neuroscience (Pages 719-746). Madrid: Médica Panamericana S.A.
- Leon-Carrión, J., & Barroso, J. (1997). Neuropsychology of Thought. Seville: KRONOS.
- Redolar, D. (2014). Frontal lobes and their connections. In D. Redolar, Cognitive Neuroscience (Pages 95-101). Madrid: Médica Panamericana S.A.