The Fascinating World of Executive Functions

Executive function is an umbrella term, referring to those high-level processes that control and organise other mental processes - Neuropsychology

ID Articolo: 42551 - Pubblicato il: 29 aprile 2014
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Elena Lo Sterzo

 

 

The Fascinating World of Executive Functions Executive function is an umbrella term, referring to those high-level processes that control and organise other mental processes, that facilitate new ways of behaving and optimise one’s approach to unfamiliar circumstances.

Years of observation at behavioural performances of patients with different type of lesions at frontal lobe, along with investigations with neuroimaging techniques, have led to confidently hypothesize that these processes are supported by structures within the frontal lobes on the brain.

Most theories of executive function are based on a distinction between automatic and controlled processing. Routine processing refers to mental operations that are overlearned, such as reading out a word. On the other hand, non-routine processing most commonly refers to mental operations that are used in situations when there is not a well-established stimulus-response association, or where a behavioural impasse occurred.

Flexible representations of goals and intentions are at an abstract level of processing. Such higher-level representations are often contrasted with lower-level cognitive processes involved in analysing specific perceptual inputs and generating specific motor outputs.

According to most theories, executive function involves the modulation of lower-level processes by those at a higher level, allowing us to behave flexibly, rather than being slaves to our environment. The executive system has been traditionally quite hard to define, since there is no single behaviour that can in itself be tied to executive function (or indeed executive dysfunction).

One of the most influential framework for understanding executive functions has been offered by Norman and Shallice (1986): they proposed that behaviour is governed by sets of thought or action schemas (a set of actions or cognitions that became very closely associated through practice.)

These schemas can be triggered by events in one’s environment and can be sufficient to behave appropriately in routine situations involving well-learned links between particular events in our environment and particular ways of behaving. However, in situations involving novelty or where well-learned responses need to be inhibited, environmental triggering is insufficient and a second system is required to modulate the activity level of schemas. Norman and Shallice called this the supervisory system and suggested that it is supported by the frontal lobes of the brain.

Another theoretical model for understanding executive functions has been put forward by Duncan (2001): according to its adaptive coding model, the prefrontal cortex (PFC) has a remarkable ability to adapt its function to the current task, thus PFC is viewed as “global workspace” that, rather than multiple executive processes, can adapt to many different cognitive operations.

Messaggio pubblicitario Determining the relative contributions of different frontal subregions to different executive functions is a highly complex matter, but on current evidences, some suggestions can be put forward. Ventrolateral PFC (VLPFC) is thought to be involved in comparatively simple tasks, such as short-term maintenance of information that cannot currently be perceived in working memory. By contrast, dorsolateral PFC (DLPFC) has been most commonly implicated in manipulating that information. DLPFC has also been suggested to be involved in complex functions such as making plans for the future.

The largest and most mysterious, sub-region of prefrontal cortex is the rostral PFC (RPFC): patients with damage restricted to the RPFC often perform well on standard neuropsychological tests, including classical tests of executive function such as the Wisconsin card sorting test (Grant & Berg, 1948). Instead, patients with damage to this region seem to have particular difficulties in real-world multitasking situations (e.g. Multiple errands test, Shallice & Burgess, 1991), such as organizing a shopping trip when there are few strict constraints but also multiple instructions to be remembered, and potential distractions in the environment.

Recent accounts have focused on the role of RPFC in the most high-level human abilities, such as combining two distinct cognitive operations in order to perform a single task, trying to work out what other people are thinking (mentalizing), and reflecting on information we retrieve from long-term memory (source memory).

Interestingly, the gateway hypothesis proposed by Burgess et al. (2005) claims that RPFC is involved in modulating the attentional balance between stimulus-oriented and stimulus-independent information (i.e. information that we perceive in our environment and information that we represent internally).

Finally, although we now have a much greater understanding of the ways in which executive functions can be split into various discrete processes, and the ways in which PFC can be split into functionally discrete subregions, further researches are needed in order to deepen the functions of prefrontal cortex in explicit computational terms: not just knowing that a particular region of PFC supports a particular ability, but also clarifying how it happens.

 

 RELATED TOPICS:

FUNZIONI ESECUTIVE – ENGLISH ARTICLES

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