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Executive Functions: Definition; Contexts and Neuropsychological Profiles
Definition and clinical context of
executive functions
The term “executive functions”
(E.F.) refers to a complex cognitive construct in the form of a system
organized in functional modules of the mind; where a series of processes
necessary to maintain an appropriate; organized and flexible planning mode are included.
resolution (or problem solving); control and coordination; aimed at a purpose
[1-3].
To simplify; the executive
functions are those abilities that answer the question << Who is in
charge? >> and concern mental processes aimed at the elaboration of
adaptive cognitive-behavioral schemes; at the base of planning; decision
making; working memory; corrective response to error feedback; predominant
habits; mental flexibility.
This complex construct thus
implies:
a. An ability to inhibit a
response or to postpone it at a later and more appropriate time.
b. A strategic and flexible
planning of behavioral sequences.
c. A mental representation of the
task that includes both the relevant information encoded in the memory and the
future objectives to be achieved.
There are several possible
definitions; from a theoretical and organizational point of view [4]:
1) The executive functions
represent a system of abilities that allows to create objectives; to preserve
them in memory; to control the actions; to foresee the obstacles and to reach
objectives (Stuss 1992).
2) Executive functions represent
the set of abilities that allow the person to successfully implement
independent; intentional and useful behaviors (Lezak 1993).
3) Executive functions are higher-order
cognitive functions that make it possible to formulate objectives and plans;
remember these plans over time; choose and start actions that allow us to reach
those goals; monitor the behavior and adjust it so as to arrive at those goals
(Aron 2008).
It therefore appears evident that
the executive functions are not easy to define; since this term does not refer
to a single capacity but rather to a set of different sub-processes necessary
to perform a specific task. They are superior cortical functions responsible
for the control and planning of behavior; they are processes that allow the
person to plan and implement projects aimed at achieving a goal and are
necessary because they guarantee the monitoring and modification of their
behavior in case of need or they adapt it to new contextual situations.
1) Analyzing the task.
2) Plan how to achieve the task.
3) Organize the steps needed to
carry out the task in question.
4) Develop a timeline to complete
the task.
5) Adjust or change steps; if
necessary; to complete the task.
6) Complete the task in a timely
manner.
They are therefore executive
functions surely:
a) The inhibition; or the ability
to focus attention on the relevant data ignoring the distractors and inhibiting
inadequate or impulsive motor and emotional responses with respect to stimuli.
c) Planning; or the ability to
formulate a general plan and organize actions in a hierarchical sequence of
goals.
d) The working memory; or the
ability to activate and maintain the plan and the work area at a mental level;
to have a mental reference set on which to work mentally.
e) Attention; or the ability to
maintain concentration on a given element.
f) Fluency; or the ability of
divergent thinking and ability to generate new and different solutions with
respect to a problem [5].
Although those most investigated
for information on cognitive functioning are the basic functions of working
memory [6] (or updating; the ability to maintain; update and process
information in mind in time for the resolution of a task); of cognitive
flexibility (or shifting; the ability to pass from one mental operation to
another by controlling the mutual interference between the two actions) and
inhibition (or inhibition; the ability to control automatic responses that
interfere in achieving of a purpose); the executive domain does not end with
the only cognitive processes listed above; but also involves mechanisms that
play a part in the regulation of emotions; behavior and motivation.
a) The “Cool” executive functions
represent those functions based on a complex; cognitive; controlled and slower
processing; which are activated when the subject is dealing with abstract and
decontextualized problems. The neurophysiological area used for these functions
is the dorso-lateral prefrontal cortex [7].
b) The “Hot” executive functions
are linked to an automatic and emotional processing of the stimuli; or a simple
and rapid programming that intervenes in situations of stress; these functions
are required in significant situations and involved in the regulation of
emotion and motivation. The neurophysiological area used for these functions is
the ventromedial prefrontal cortex [8].
The “Hot” executive functions and
the “Cool” executive functions; according to this theoretical construct; work
synchronously in order to guarantee an ideal functioning; but
neuropsychological studies suggest a double dissociation between the two types
of functions; documenting injuries on load Hot in the absence of problems
against the Cool and the Cool in the absence of Hot.
The advances in the methodological
field and in particular the conception of experimental tests with motor;
linguistic and memory requirements; compatible with the level of competence of
the child in early childhood; have allowed us to observe how the development of
executive functions begins earlier; compared to what was previously assumed;
this applies to both the Cool and the Hot ones. As far as the Cool is
concerned; we have already seen how at 12 weeks the child is able to preserve
the memory of the objective structure of an event in which he was the
protagonist to reuse it in similar situations; from seven to eight months the
first signs of working memory and inhibitory control begin to appear; regarding
the Hot; some observations seem to suggest difficulties in the control of this
executive domain in the first two years of life; although the processes of
cortical development seem to affect these regions before those involved in the
Cool: the child would indeed have difficulty in regulating the emotions and in
postponing rewards/gratifications and presenting a way of relating to the
self-centered world. Between the ages of three and five; the child succeeds in
tasks that require maintaining information in the mind and at the same time the
capacity for inhibition; between three and four years the ability to generate
concepts develops; between four and five years the attentional control matures
and there is an improvement in cognitive flexibility and in the ability to
formulate strategies; at five years there is an increase in working memory and
therefore in the ability to temporarily preserve and manipulate information
online.
With preadolescence some executive
skills reach maturity. Between seven and eight years and between nine and
twelve years there is an increase in sensitivity to feedback in
problem-solving; in the formulation of concepts and in the control of
impulsiveness. At the age of seven; considerable progress has been reported in
the speed of execution; in the ability to use the strategies; in the ability to
maintain information in the mind and to work with it. Between the ages of eight
and ten adult levels are reached in cognitive flexibility and at ten years the
ability to maintain the set; the verification of hypotheses and impulse control
is manifested; there is an improvement in the inhibitory control; in the
vigilance and in the attention sustained between the eight and eleven years;
period in which besides is assisted to an improvement in the performances tests
that conjugate inhibitory competences and working memory; this last one suffers
further efficiency improvements between nine and twelve years.
An improvement in the ability to
understand emotions; intentions; beliefs and desires is noted in this period.
Between thirteen and fifteen years there is an increase in memory strategies;
in its efficiency; in time planning; in problem-solving and in the search for
hypotheses. Furthermore; verbal fluency and the ability to plan complex motor
sequences mature at the age of twelve. The changes of this period; both on the
cognitive and the executive side; allow the person to cope with the new and
growing demands that the physical and social environment put on him;
experiencing a sense of independence; responsibility; and social awareness.
At fifteen years there is an
improvement as regards attentional control and processing speed as well as
maturation in inhibitory control. Between the ages of sixteen and nineteen;
progress is made in working memory; problem-solving and strategic planning.
From an executive point of view; Hot improves the ability to make decisions in
the presence of rewards and losses. Between the ages of twenty and thirty;
working memory; planning; problem-solving and the ability to implement targeted
behaviors reach higher levels of functioning.
As regards the Hot Executive
functions; the achievement of mature decision-making levels is achieved. With
aging there is a gradual deterioration in some cognitive areas including the
Executive Functions; although some changes are not evident before eighty years
even though the brain degenerative process begins in the third decade of life.
Between the ages of thirty and forty-nine; there is a decrease in information
storage and temporal sequencing skills; the ability to formulate concepts;
organization; planning and attentional shifting worsen between the fifty-three
and sixty-four years. Starting from the age of sixty-five; memory difficulties
are reported [9-11].
It is good to underline however
that even today we think of the executive system and the attention system as
separate entities: attention would act on sensory information and on internal
representations while the executive system on behavior. If the attentional
aspects allow the executive functions to mature; the executive system is seen
as a form of attention directed towards oneself. Therefore, the development of
E.F. involves a consolidation of intellectual cognitive abilities; learning and
memories.
The Neural Correlates in Eating
Disorders [12]
If neuroscience has been trying
for decades to associate specific brain functions with specific brain areas;
with the relative recent advent of functional neuroimaging and brain mapping;
this commitment seems to have become dominant; however; the debate on the
selective localization of complex faculties remains open; despite their
historical location; identified in the so-called frontal lobe syndrome; even
preceded the formulation of the construct (Galati; Tosoni; 2010); in fact;
traditionally; they were classified as executive disorders those following
damage in the prefrontal cortex.
Recent studies of neuroimage
(Galati; Tosoni; 2010); carried out on healthy people through classical
neuropsychological tests for the examination of E.F. reveal; however; also the
activation of the posterior parietal cortex and of various subcortical centers;
in addition to the areas of prefrontal cortex; whose functional subdivisions;
however; still remain difficult to identify; due to its anatomy and its
heterogeneous functionalities. In particular; the studies show that the frontal
lobes are functionally connected with: the posterior parietal cortex; which
appears to be involved in the reconfiguration of the responses and in the
behavioral modifications (Sohn et al; 2000; Barber and Carter; 2005); the basal
ganglia; the anterior cingulate; which seems particularly involved in
situations of control of cognitive conflicts between environmental stimuli or
behaviors and in the selection of agent responses in case of uncertainty
(Carter and Van Veen; 2007; Rushworth and Beherens; 2008).
The scholars of the Executive
Functions; therefore; remain cautious about their specific localization;
preferring to believe that they are implemented in multiple distributed
circuits; each of which includes connections with some portion of the
prefrontal cortex (Galati; Tosoni; 2010; p. 36.). The same Luria (1962) who; on
the basis of numerous clinical observations; first theorized the existence of a
central control system for some higher order functions; such as planning;
monitoring; self-regulation; involved more involvement interconnected cortical
and subcortical areas: prefrontal cortex; cerebellum; some subcortical nuclei.
Therefore; the study on the
functions performed by the prefrontal cortex remains open. It is believed that
the executive functions are anatomically related to different areas of the
prefrontal cortex; and to the associated cortico-subcortical circuits:
a) The dorso-lateral prefrontal
area would be particularly involved in the abstraction and planning of actions.
b) The orbital-frontal area would
be involved in the regulation of emotions and decision-making processes.
c) The anterior cingulate area
(especially in the dorsal part) would be involved in the control of motivation
and interfering stimuli.
The empirical evidences derived
from the neuropsychological approach and from the neuroimaging show however
that the executive functions connected to the orbito-frontal cortex mature
early with respect to the executive functions connected to the dorso-lateral
pre-frontal cortex [13]. An interesting review of 2006 takes in detail; albeit
dated; the cognitive; affective and behavioral correlates of brain maturation
that occurs during adolescence. This maturation; due to phenomena of
myelination and synaptic pruning; is particularly accentuated in the prefrontal
cortex; the main site of decision-making processes. If the executive functions
and the decision-making processes are based on the functioning of prefrontal
areas; which change considerably during adolescence; it can be hypothesized
that the decision-making abilities of adolescents are still immature, and this
may explain their risky behavior. This hypothesis is discussed; also, in
relation to the onset of psychopathological disorders in this age group [14].
The Clinical and Strategic
Approach in the Management of Executive Function Deficits [15]
Following an injury or dysfunction
in the frontal lobes; due for example to a head injury; a degenerative
pathology or a neoplasm; the patient can show the symptoms of what is called
“frontal syndrome”. Frontal syndrome is a clinical picture characterized by
cognitive deficits and / or behavioral; emotional and motor disorders.
Studies on adult patients with
lesions in different areas of the prefrontal cortex show; in fact; partially
different neuropsychological pictures:
1) Lesions in the anterior orbital
part; in general; cause personality modifications and disinhibition.
2) The lesions in the
orbito-frontal part; also because it is closer to the amygdala; to the
hippocampus and to the hypothalamus; areas that mediate between internal states
and environmental stimuli; generally present inattentive; impulsive behaviors;
difficulty in problem solving and in taking of decisions; serious antisocial
conduct.
3) Lesions in the medial part;
including the anterior cingulate gyrus; cause poor motor control and difficulty
in maintaining focused attention.
4) The laterals of the prefrontal cortex present action planning disorders; especially related to the management of mental representations useful for achieving a purpose and the difficulties related to written and spoken language are understood.
The lesions of the frontal cortex;
caused by expansive processes of tumor; vascular or hypoxic origin; or cranial
traumas or degenerative processes of the nervous system; therefore, lead to
deficits in executive functions; in particular problems:
a) In planning and problem
solving: the person has difficulty planning and executing a sequence of actions
to reach a goal; but also in the planning of sequences of movements.
b) In cognitive flexibility: it
has a rigid; non-flexible behavior and puts into effect perseverances; always
giving the same answer or using the same strategy even when it proves
inadequate.
c) In the working memory: the
memory disorders that can be classified in the frontal amnesic syndrome are
characterized by the inability to retain new information; greater
distractibility and confabulations; difficulty in using memorization
strategies; inability to know how to use the new acquired data; incapacity to
memorize voluntarily.
d) In the inhibition of automatic
behaviors not congruent with the situation: it is the case of the
“environmental syndrome” or “dependence of use”: placed for example in front of
objects that it is used to use; the person uses them without any invitation and
without any reason (for example; a patient who in front of a bottle of water
placed on the examiner’s desk; takes it and drinks it).
e) In decision-making: the
difficulty of deciding in an advantageous way for oneself and of respecting
social norms is understood (Bechara et al. 2000; Rolls; 2000). Patients with
this disorder are more likely to make risky choices and develop; for example; a
gambling addiction.
f) In the regulation of emotions
and behavior: we can have a patient who shows a picture of disinhibited type
symptoms characterized by euphoria; restlessness; sexual disinhibition;
inappropriate social behavior; poor interest in others; uninhibited behavior;
with little impulse control; easy irritability and aggressiveness; euphoria;
emotional lability; or an apathetic type symptomatology with a
“pseudo-depressed” personality; therefore with modifications characterized by
indifference; apathy; decreased spontaneity; reduced sexual interest; reduced
expression of emotions; decreased verbal productivity (including mutism);
decreased motor behavior.
g) Low self-criticism and
judgment: the person have a deficit in judging reality; especially when the
situation is new or complex and a lack of critical attitude towards the actions
carried out. It also shows difficulty in correcting its errors and inability to
modify or schedule new behaviors.
In some syndromes then there are
deficits in executive functions; such as in autism and dyslexia; Executive
deficits have been detected in attention deficit / hyperactivity disorder
(ADHD); schizophrenia and conduct disorder. It is thought that many mental
disorders are associated with this type of deficit; although in every disorder
it is likely to change the degree to which each component of executive
functions is involved. Deficits related to executive functions can be
manifested in behavioral symptoms such as: environmental dependence syndrome;
with use behavior; that is; as soon as the subject notices an object that he is
used to using in a certain way; he uses it; even if the context would require a
inhibition of this behavior (eg the subject goes to the doctor and as soon as
he notices the window opens it; without a precise reason); and imitation
behaviors; that is; the subject spontaneously imitates the gestures of the
person in front of him; hypoactivity; such as apathy or anhedonia (in which the
person does not perform behaviors that would also give him gratification (such
as activities related to food or affective activities); hyperactivity; ie
distractibility; impulsiveness; disinhibition. In general; the behavior may
appear disorganized [16].
Compared to the diagnosis;
however; one must rely on a series of neuropsychological tests; including the
Trail making test (versions A and B). The other tests that are most used for
the evaluation of the executive functions are: the Tower of London that proves
the ability of planning; problem solving and inhibition; the dimentional change
card sort test; which is a task that evaluates flexibility; the matching
familiar figure test that evaluates the use of visual search strategies;
control of the impulse response and interference [17].
Conclusion
The E.F. they represent an
important field of research and clinical work in the field of cognitive
developmental neuropsychology. There are numerous attempts to summarize the common
characteristics of the skills related to E.F.: the ability to inhibit
overbearing responses and to organize behavior based on arbitrary rules [18];
the ability of the “central executive” to select the appropriate schemes of
action from a repertoire activated by specific inputs [19].
The hypothesis of the
multidimensionality of FEs [20-22] is increasingly accepted and several studies
are highlighting the evolutionary trajectories of the different subdomains in
the typical development; starting to outline a staged process with a complex
hierarchical organization. In the clinical field the impairments of the E.F.
they are related to numerous cognitive and behavioral difficulties: limited
sustained attention; perseverative responses; impaired initiation of actions;
poor use of feedback; difficulties in planning and organization; problems
related to the storage and manipulation of mental representations. Furthermore;
studies on the impairment of E.F. in neurodevelopmental disorders.
These include autism and DGS; in
which the E.F. they appear to be pervasive in different domains; severe and
pre-existing over time. Other developmental disorders seem to show a more
specific profile; with the impairment of some subdomains: the A.H.D.; with the
deficit in inhibition; represents one of the most studied cases. For other
disorders the research results are more controversial. The differences in the
profiles of the E.F. in these disorders they support the hypothesis of a
fraction ability of E.F. in subdomains; at least partially independent. It
should also be specified that the various subdomains have not been fully
studied in all the disorders. Despite these limitations; at least partially
specific “executive profiles” of various disorders are emerging [23].
A greater knowledge of these
profiles and their evolutionary trajectories; combined with an attention to
“ecological validity”; can allow us a greater understanding of the mental
functioning of children with typical and atypical development; with potential
relapses in the diagnostic and therapeutic-rehabilitative field [24- 26].
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