In cognitive science and neuropsychology, executive functions (collectively referred to as executive function and cognitive control) are a set of cognitive processes that support goal-directed behavior, by regulating thoughts and actions through cognitive control, selecting and successfully monitoring actions that facilitate the attainment of chosen objectives. Executive functions include basic cognitive processes such as attentional control, cognitive inhibition, inhibitory control, working memory, and cognitive flexibility. Higher-order executive functions require the simultaneous use of multiple basic executive functions and include planning and fluid intelligence (e.g., reasoning and problem-solving).
Executive functions gradually develop and change across the lifespan of an individual and can be improved at any time over the course of a person's life. Similarly, these cognitive processes can be adversely affected by a variety of events which affect an individual. Both neuropsychological tests (e.g., the Stroop test) and rating scales (e.g., the Behavior Rating Inventory of Executive Function) are used to measure executive functions. They are usually performed as part of a more comprehensive assessment to diagnose neurological and psychiatric disorders.
Cognitive control and stimulus control, which is associated with operant and classical conditioning, represent opposite processes (internal vs external or environmental, respectively) that compete over the control of an individual's elicited behaviors; in particular, inhibitory control is necessary for overriding stimulus-driven behavioral responses (stimulus control of behavior).Figure 4: Executive functions and related terms The prefrontal cortex is necessary but not solely sufficient for executive functions. Contemporary neuroscience research further supports the view that executive functions rely on distributed neural networks rather than a single brain region. While the prefrontal cortex plays a central role, other regions such as the subcortical structures, interact dynamically to support cognitive control. This perspective reflects a shift away from localized models toward understanding executive function as a property of coordinated brain activity.Diamond, A. (2013). Executive functions. Annual Review of Psychology. DOI: 10.1146/annurev-psych-113011-143750 for example, the caudate nucleus and subthalamic nucleus also have a role in mediating inhibitory control.
Cognitive control is impaired in addiction, attention deficit hyperactivity disorder, autism, dyscalculiaGoldfarb, L. Cognitive interferences and their development in the context of numerical tasks: review and implications. Heterogeneity of function in numerical cognition, 245–262.Szucs, D., Devine, A., Soltesz, F., Nobes, A., & Gabriel, F. (2013). Developmental dyscalculia is related to visuo-spatial memory and inhibition impairment. Cortex, 49(10), 2674–2688. https://doi.org/10.1016/j.cortex.2013.06.007 and a number of other central nervous system disorders. Stimulus-driven behavioral responses that are associated with a particular rewarding stimulus tend to dominate one's behavior in an addiction.
Neuroanatomy Historically, the executive functions have been seen as regulated by the prefrontal regions of the frontal lobes, but it is still a matter of ongoing debate if that really is the case. Even though articles on prefrontal lobe lesions commonly refer to disturbances of executive functions and vice versa, a review found indications for the sensitivity but not for the specificity of executive function measures to frontal lobe functioning. This means that both frontal and non-frontal brain regions are necessary for intact executive functions. Probably the frontal lobes need to participate in basically all of the executive functions, but they are not the only brain structure involved.
Neuroimaging and lesion studies have identified the functions which are most often associated with the particular regions of the prefrontal cortex and associated areas. The dorsolateral prefrontal cortex (DLPFC) is involved with "on-line" processing of information such as integrating different dimensions of cognition and behavior. As such, this area has been found to be associated with verbal and design fluency, ability to maintain and shift set, planning, response inhibition, anticipation of conflict stimuli, working memory, organisational skills, reasoning, problem-solving, and abstract thinking.
The anterior cingulate cortex (ACC) is involved in emotional drives, experience and integration. Associated cognitive functions include inhibition of inappropriate responses, decision making and motivated behaviors. Lesions in this area can lead to low drive states such as apathy, abulia or akinetic mutism and may also result in low drive states for such basic needs as food or drink and possibly decreased interest in social or vocational activities and sex. The orbitofrontal cortex (OFC) plays a key role in impulse control, maintenance of set, monitoring ongoing behavior and socially appropriate behaviors. The orbitofrontal cortex also has roles in representing the value of rewards based on sensory stimuli and evaluating subjective emotional experiences. Lesions can cause disinhibition, impulsivity, aggressive outbursts, sexual promiscuity and antisocial behavior.
Furthermore, in their review, Alvarez and Emory state that:The frontal lobes have multiple connections to cortical, subcortical and brain stem sites. The basis of "higher-level" cognitive functions such as inhibition, flexibility of thinking, problem solving, planning, impulse control, concept formation, abstract thinking, and creativity often arise from much simpler, "lower-level" forms of cognition and behavior. Thus, the concept of executive function must be broad enough to include anatomical structures that represent a diverse and diffuse portion of the central nervous system.The cerebellum also appears to be involved in mediating certain executive functions, as do the ventral tegmental area and the substantia nigra.
In humans, high contents of cannabinoid receptor 1 (CB1) is found in frontal neocortical areas, subserving higher cognitive and executive functions, and in the posterior cingulate, a region pivotal for consciousness and higher cognitive processing by its activation.
Hypothesized role
The executive system is thought to be heavily involved in handling novel situations outside the domain of "automatic" psychological processes that could be explained by the reproduction of learned schemas or set behaviors. Psychologists Don Norman and Tim Shallice have outlined five types of situations in which routine activation of behavior would not be sufficient for optimal performance: Those that involve planning or decision-making Those that involve error correction or troubleshooting Situations where responses are not well-rehearsed or contain novel sequences of actions Dangerous or technically difficult situations Situations that require the overcoming of a strong habitual response or resisting temptation.
A prepotent response is a response for which immediate reinforcement (positive or negative) is available or has been previously associated with that response.
Executive functions are often invoked when it is necessary to override prepotent responses that might otherwise be automatically elicited by stimuli in the external environment. For example, on being presented with a potentially rewarding stimulus, such as a tasty piece of chocolate cake, a person might have the automatic response to take a bite. However, where such behavior conflicts with internal plans (such as having decided not to eat chocolate cake while on a diet), the executive functions might be engaged to inhibit that response.
Although suppression of these prepotent responses is ordinarily considered adaptive, problems for the development of the individual and the culture arise when feelings of right and wrong are overridden by cultural expectations or when creative impulses are overridden by executive inhibitions.
Historical perspective
Although research into the executive functions and their neural basis has increased markedly over recent years, the theoretical framework in which it is situated is not new. In the 1940s, the British psychologist Donald Broadbent drew a distinction between "automatic" and "controlled" processes (a distinction characterized more fully by Shiffrin and Schneider in 1977), and introduced the notion of selective attention, to which executive functions are closely allied. In 1975, the US psychologist Michael Posner used the term "cognitive control" in his book chapter entitled "Attention and cognitive control".
The work of influential researchers such as Michael Posner, Joaquin Fuster, Tim Shallice, and their colleagues in the 1980s (and later Trevor Robbins, Bob Knight, Don Stuss, and others) laid much of the groundwork for recent research into executive functions. For example, Posner proposed that there is a separate "executive" branch of the attentional system, which is responsible for focusing attention on selected aspects of the environment. The British neuropsychologist Tim Shallice similarly suggested that attention is regulated by a "supervisory system", which can override automatic responses in favour of scheduling behaviour on the basis of plans or intentions. Throughout this period, a consensus emerged that this control system is housed in the most anterior portion of the brain, the prefrontal cortex (PFC).
Psychologist Alan Baddeley had proposed a similar system as part of his model of working memory and argued that there must be a component (which he named the "central executive") that allows information to be manipulated in short-term memory (for example, when doing mental arithmetic).
Development
The executive functions are among the last mental functions to reach maturity. This is due to the delayed maturation of the prefrontal cortex, which is not completely myelinated until well into a person's third decade of life. Development of executive functions tends to occur in spurts, when new skills, strategies, and forms of awareness emerge. These spurts are thought to reflect maturational events in the frontal areas of the brain. Attentional control appears to emerge in infancy and develop rapidly in early childhood. Cognitive flexibility, goal setting, and information processing usually develop rapidly during ages 7–9 and mature by age 12. Executive control typically emerges shortly after a transition period at the beginning of adolescence. It is not yet clear whether there is a single sequence of stages in which executive functions appear, or whether different environments and early life experiences can lead people to develop them in different sequences.
Early childhood Inhibitory control and working memory act as basic executive functions that make it possible for more complex executive functions like problem-solving to develop. Inhibitory control and working memory are among the earliest executive functions to appear, with initial signs observed in infants, 7 to 12 months old. Then in the preschool years, children display a spurt in performance on tasks of inhibition and working memory, usually between the ages of 3 and 5 years. Also during this time, cognitive flexibility, goal-directed behavior, and planning begin to develop. Nevertheless, preschool children do not have fully mature executive functions and continue to make errors related to these emerging abilities – often not due to the absence of the abilities, but rather because they lack the awareness to know when and how to use particular strategies in particular contexts.
Preadolescence