How are attention and executive functions structured? - Chapter 10

What is attention?

Attention is not a homogenous unitary concept. It is the selection of relevant information from an internal (thoughts and memories) or external (image) source. According to van Zomeren and Brouwer (1994), a distinction can be made between the selectivity and intensity of attention. Attention processes are driven by the executive functions: functions that are strongly involved in planning and regulating behavior in new and complex situations.

What is selectivity of attention?

It is necessary that the relevant information is distinguished from the irrelevant information due to the limited capacity of attention. Attention can be passively drawn to some event (bottom-up control), and an active, intentional form (the top-down control) in which the person intentionally and voluntarily focuses his / her attention on self-selected stimuli. According to Broadbent's theory (1958), all information is processed in parallel up to the bottleneck, after which only the relevant information is further processed and the noise signals are omitted. Selection also takes place on the basis of a combination of different stimulus characteristics. This process is called 'pigeonholding'.

The difference between focused attention and divided attention

At the behavioural and task level, two aspects of selectivity can be distinguished: focused attention and divided attention. According to recent research, "multitasking" does not occur, and in divided-attention conditions the attention is quickly switched from one task to the other.  

The difference between controlled and automatic information processing

According to Shiffrin and Schneider (1977) there are two information processing processes: the (conscious, slow) controlled information processing and the (unconscious, fast) automatic processing. Automatic information processing makes it possible for tasks to be performed simultaneously without the disruptive factor of interference. Controlled information processing requires executive skills.

Which concepts are important for intensity of attention?

Alertness

Within the intensity of attention, a distinction is made between alertness (the receptivity of the central nervous system to stimulation), phasic fluctuations (short-term changes that are mainly introduced by the situation) and tonic fluctuations (occur over longer periods of time and are determined by the state of the organism rather than by the situation). 

Sustained attention

Factors that are used to measure the capacity to hold attention for longer periods of time are: the 'time on task' effect (the extent to which performance on a sustained-attention task deteriorates over time), the task-performance variability and the alertness during vigilance tasks.

The neuroanatomical model

According to the neuroanatomical model of attention by Posner and Petersen (1990) there can be identified three functional attention networks:

1. The 'vigilance network' (alertness): involved areas of the brain are the brainstem, the locus coeruleus, the intralaminar thalamic nuclei, and the right hemisphere (in particular the right lateral frontal lobe).

2. The posterior attention network (the focusing of visuospatial attention): the posterior parietal cortex, the pulvinar, and the superior colliculus.

3. The anterior attention network (the active selective detection of information): this system mainly appeals to the frontal part of the cingulum and the supplementary motor cortex.

What are executive functions?

Executive functions (so-called by Lezak in 1982) are used especially in new and complex situations, because they are mainly involved in tasks that require planning, error detection, problem solving, and adjustment. As already pointed out in the model by Posner and Peterson (1990), executive functions are mainly located in the prefrontal brain areas (the anterior attention network). Luria (1966) also assumed the prefrontal lobes to play a supervisory role. These areas are part of the neural networks in which many other structures also play a role, in other words: the executive functions are in essence a psychological construct, and cannot be compared to frontal functioning. Related functions that are located in the prefrontal areas are motivation and initiative (the 'cold cognitive functions'). The social cognitions (the 'warm cognitive functions') also demand the strong involvement of the frontal lobe. It is difficult to distinguish between social cognition and executive functions.

Which unitary theories are known about executive control?

According to the mental schema theory of Norman and Shallice (1986), all human thinking and actions are the result of activated mental schemes (programs or routines) that are activated by the most relevant external stimuli. The 'excitability' of the schemes depends on three factors: competition selection (contention scheduling), lateral modulation, and the supervisory attentional system (SAS). Competition selection assumes that selection of schemes is an automated process and depends on the 'strength' of the scheme (this is obtained by the amount of previous activations): the strongest scheme wins. Lateral modulation means that one schedule (going to the cinema) influences other schedules: it can suppress a schedule (scream hysterically) or, on the contrary, facilitate (be quiet and watch the movie) depending on the situation. These two factors determine the schedule selection in routine situations. In a non-routine situation, the higher-order SAS is activated: a conscious choice is now required to select the schemes.

Which fractionation theories of executive functions are known?

Both the Baddeley (1986) model and the Norman and Shallice (1986) model are unitary theories: there is one central control system. Nowadays more and more theories are emerging that are based on a so-called 'multifaceted' concept of executive functions. For example, Miyake, Friedman, Emerson, Witzki and Howeter (2000) proved that three separate executive components can be distinguished: mental flexibility (shifting), inhibition, and updating of the working memory. The problem of fractionation of executive functions through analysis of neuropsychological tasks is that the tasks do not cover all aspects of executive functioning. A conceptual layout may therefore be more appropriate and clinically applicable. Ylvisaker (1998) distinguishes the following eight executive components within this theoretical framework:

1. Insight into and awareness of one's own capacities and requirements.

2. The setting of clear and realistic, concrete goals.

3. The planning of the task steps that will result in these goals.

4. Taking the initiative to execute these plans.

5. Self-monitoring and evaluation of the implementation in accordance with the goal and plan.

6. Self-inhibition of behaviour that does not result in the goal.

7. Flexibility and the ability to solve problems when the situation does not develop according to plan.

8. Strategic behaviour, or the ability to apply successful behaviour independently in other situations.

Where are attention and executive functions located?

What role does the prefrontal cortex play in executive functioning?

Not only the prefrontal cortex (PFC) is involved in executive functioning; other (subcortical and cortical) brain areas are also necessary for healthy executive functioning. According to Tekin and Cummings (2002), three sub-regions of the prefrontal cortex - the dorsolateral prefrontal cortex (DLFPC), the orbitofrontal cortex (OFC) and the anterior cingulate cortex (ACC) - work together with subcortical areas to form a subfunction of executive functions to be carried out. The DLPFC is mainly involved in the correct execution of tasks (and therefore among other things: focusing attention, keeping the information in the working memory active, “updating” the working memory, planning, monitoring and using feedback). The OFC (which also includes the ventromedial prefrontal cortex or VMPFC) is primarily activated during social cognition (which includes adjusting cognitive behavior after negative feedback and processing reward-related information). The ACC is strongly involved in taking the initiative and the possibility of self-motivation.

Which other brain areas play a role in executive functioning?

The PFC has is strong connected to the basal ganglia and the cerebellum (via the thalamus). Both Tekin and Cummings (2002) and Ekin (2003) emphasize the important role of the basal ganglia and the striatum when talking about executive functions. In addition, the parietal cortex also plays a major role as an important part of a so-called frontoparial control network.

Which disorders exist with regard to attention and executive functioning?

An unpleasant problem after brain injury or brain disease is the delayed processing of information (mental slowness) that adversely affects other cognitive functions. This is particularly unpleasant in conducting attention tasks since these often have time limits. If there is a problem in focusing attention, the performance on a task should be much worse with distraction than without distraction. Alzheimer patients and patients with frontal damage or frontally located CVAs have an increased deductibility and are less able to ignore stimuli than controls. Disorders in sustained attention, uncovered by the go / no-go paradigm, are common after frontal traumatic brain injuries. A disorder in executive functioning, a dysexecutive syndrome (replacing the outdated term "frontal syndrome"), includes serious disorders in the aspects described by Ylvisaker (1998). Functioning independently is virtually impossible: plans are not made or implemented poorly.

How are impairments in attention and executive functioning caused?

Disorders in executive functions may be due to oxygen deficiency, a brain tumor, brain inflammation, neurological disorder or traumatic brain injury, but also to neurodegenerative disorders such as Parkinson's disease. The difficulty about measuring executive disorders is the that the tests are often highly structured, while the executive functions are only properly operational when the (new, complex) situation requires structure.