In this chapter we move towards central control. We will see the role played by the frontal lobes in the coordination of information coming from other areas of the brain, fundamental to understanding the moral and ethical conduct, so necessary to live in society.
Frontal lobes and central executive
Following the accident of Phineas Gage in 1848, in which an 1 iron bar entered his head while he was working on the construction of the railroad, the importance of the frontal lobe in the behavior of the human being has been seen. In this case, in addition to surviving the accident, he had hardly any loss of motor or intellective functions, except that he went from being a very responsible person to being very impulsive, violent and irresponsible.
Since then it was seen that the frontal lobe plays an important role in the executive process.
By studying other patients with similar alterations in the frontal lobe, a particular picture could be described, a process with loss of control in itself, highlighting the inability to establish a sequence of activities in the achievement of objectives, which is what has been called "Frontal lobe syndrome" Today we know that the affected part is not the entire lobe but the most anterior region, the prefrontal cortex (PFC), located in front of the motor and supplementary motor areas.
The prefrontal cortex
The prefrontal cortex occupies a large size which makes us think about the importance of its functions, being able to represent the executive part of the working memory. The prefrontal cortex receives information from practically all the brain, perceptual, motor and subcortical regions and, in turn, forwards connections to all these regions.
One way to assess frontal damage is by testing the letters from Wisconsin. When the prefrontal cortex is altered, there is a decrease in the efficiency in the classification of the letters when changing the attribute to classify.
Another interesting test is that of Tower of Hanoi in which these patients need to do many more movements than a healthy person. The study of patients with alterations in the frontal lobe shows the role of the prefrontal region in executive functions, basically in processes such as the initial phases of Alzheimer's disease (AD) or executive dysfunctions.
Five are the fundamental executive processes:
- The executive attention.
- The change of attention.
- The inhibition of the response.
- The temporal codification plus ordering and establishment of sequences of acts.
- The supervision.
Executive attention
Executive attention appears when competing in the control of cognition and behavior, multiple mental representations that are in the operational memory, or multiple processes that operate on the representations.
Examples we have continuously in real life and one of the most representative is chess. In it, we must decide how we move, what piece and where but, thinking not only on that play but in several in advance, thinking about the movements that our opponent will make.
To study executive attention there are different ways of doing it, one of the most used are the tasks of Stroop and, more recently, the tasks of stimulus-response compatibility.
In these tests, the fact that attention focused on something must coexist, while inhibiting the rest of the information. It seems that attention and inhibition would occur simultaneously, the problem lies in knowing if both actions use the same network and neural structures.
In real life we usually act almost automatically. In most cases there is not a multiple response in which all the options have the same force, so we should not "decide" constantly, only in case the possible answers enter "in conflict", it is when it is put in Executive attention goes on. Patients with AD are always in the conditions of automatic response, unlike healthy people who activate executive attention when required.
The neuroimaging studies in the Stroop tasks show that specific areas are activated, such as the anterior cingulate (process the conflict supervision), the dorsolateral prefrontal cortex of the right hemisphere (related to the operative memory and executive attention) and, from this region, the fusiform circumvallation is activated in the posterior area of the brain, where the color is processed. In the tasks of executive attention and motor response, the activation from the prefrontal cortex is directed to the areas of motor planning, the premotor cortex that is located behind the prefrontal cortex.
Executive attention and categorization
One of the most important functions of executive attention is to assign each object a category. This is what, theoretically, we do every time we recognize an object, we identify it by assigning it a category. However, Rips (1989) stated that there could be something more than the similarity of the object to be categorized and the corresponding representation of long term memory.
Several experiments were carried out in which the subjects had to classify (categorize), objects based on the similarity of these or based on a reasoning process and it was observed that in cases of alterations of the frontal lobe, it was still classified well by similarity but not by reasoning. These results indicated that the similarity was conserved because the mechanism used covers different areas of the cortex, while the failure in the categorization based on reasoning, indicated that executive attention, necessary in this case, was mediated by the prefrontal cortex (Grossman , 2002).
As a result of these studies, we sought to redefine the concepts of automatic and non-automatic process.
Automatic process
El automatic process is one that can be initiated in a non-deliberate way, that operates very quickly (0.5 sec to read a word, in the Stroop tests) and that can operate without consciousness (in the case of words, we should not attend to the meaning of words to identify them).
Non-automatic procesp
By contrast, a non-automatic process, also called "controlled", is a process that requires deliberation (in the Stroop example, we have to name the color in which the word is printed), it is relatively slow and requires consciousness to operate (we have to consciously attend to the color in that the word is printed).
Tasks with change of attention
Daily we find ourselves in situations where we attend to several things at the same time, changing the focus of attention quickly. A series of studies carried out by Rubenstein (2001), provide solid evidence that change of attention is a metaprocess, a process that coordinates other processes, which also provide a framework of information processing to understand the task change.
In the case of the Wisconsin test, where letters are classified according to criteria and in pure or alternating block conditions, it can be seen that there are two different levels of processing, task processing and executive processing and that the latter can influence in the first, hence the idea that executive processing is a metaprocess. At the level of task processing, it requires the following sequence of processes: identify the value of the stimulus in the crucial attribute (is the shape of a square what we see in the letter), select the appropriate response (look for the stack of the squares), and then perform the appropriate movement (place the letter in that stack of squares).
The level of executive processing, requires different processes, first, establish the reason for the trial (classify according to the form), then activate the rules that are needed to achieve the goal (meet the form), and in the case of alternate blocks , a third step is needed, establish a new objective in each trial (classify by form, classify by number, etc). In the alternating models, more time is consumed in the answers, due to this change of objectives, change in the rules, which implies a change of attention, is what is called "cost of change".
Rubenstein was able to demonstrate that there is a double dissociation between the level of task processing and that of executive processing. A given variable in a processing level does not affect the other level and vice versa, which implies that two different mechanisms are given. A variable that affects the cost of the change supposes that it acts at the level of the executive processing, whereas if it lengthens the processing of the task but not the cost of the change, it is that it only acts in the processing of the task and not in the processing of the executive .
Neural mechanisms
Neuroimaging studies complicate things a little more because although it is true that the areas that are most active in these processes are the frontal, the prefrontal cortex, they are also activated, although to a lesser degree, areas of the parietal cortex, which partially questions the preponderant role of the central executive and its exclusive location in the prefrontal cortex. All this leads us to the question of whether there are neural mechanisms common to executive attention and to the change of attention or, there would be a specific neural mechanism for each one. Studies with Sylvester's neuroimaging (2003) show that different neural mechanisms do exist.
In the tasks of change of attention, areas of the inferior parietal lobe and of the extraestriated visual cortex were activated, while in the executive attention tasks, the frontal areas, anterior prefrontal cortex and another in the premotor cortex were specifically activated. More surprisingly, the dorsolateral prefrontal cortex was not activated. Today we have evidence that the process of changing executive attention is different from that of executive attention.
These studies provide data on the role of the parietal lobes in the change of attention and, an even more relevant aspect, provide evidence that questions the most radical version of the central executive hypothesis.
Inhibition of the response
The inhibition of the response is the suppression of a partially prepared response. An example would be the one who is talking on the phone with someone who is making us angry, to a point that we are going to say a rude but, just before doing so we slow down, hold and do not say anything, we have inhibited the answer of saying a rudeness.
Studies with fMRI suggest that the inhibition of the response is an independent executive process. In the tasks of executive processing, the dorsolateral prefrontal cut is fundamentally activated and other areas, such as the anterior cingulate, secondarily. In the tasks of response inhibition, other regions different from the prefrontal cortex were activated, especially the orbitofrontal cortex, which is located under the dorsolateral PFC. When this new region is activated, the performance of tasks as in the go / no-go tests, which require inhibiting response, improved to a significant degree.
The inhibition of the response is fundamental in daily life and does not occur in childhood until the ages of 5 to 7 years and represents a significant level of maturation.
Establishment of sequences
This is a fundamental step in daily life. We can not prepare a plan to achieve an objective without coding the order of actions or events involved. The temporal order of the events in the working memory is coded. It has been seen that remembering a certain number of elements is not the same as remembering a certain sequence in which those units are arranged. The brain processing is different. In the order sequence, an executive process is required. This is verified by the fact that patients with problems in the frontal lobe can not perform sequencing and order tasks.
In daily life a high-level sequencing process is not always required. If they ask us to say the last 4 numbers of the DNI, surely what we do is visualize the whole number and then we look at the last four digits. In these cases we speak of a process of order by familiarity, different from the one that could suppose the test of pairing of letters in the analysis of sequences (Burges, 1991). When familiarity was used to represent the order of the information, by neuroimaging, activity was observed in areas of the parietal cortex, whereas when the sequence of order required a more important level of attention, executive attention, the activated area was the dorsolateral CPF. .
Our brain is adapted to organize life according to scripts or sequences, non-deterministic but quasi-established. If we go to a restaurant there is a similar sequence for everyone, we arrive, we ask for a table, we sit down, we look at the menu, we ask, we eat, we ask for the bill and we pay and we leave. If these steps are not taken, it baffles us and we see it when we tell someone about an experience, like the restaurant, even if it is secondary, we expect a sequence like the one we just saw, if we say that we paid before eating the steak that we ordered , the interlocutor is lost, is disconcerted. We see this very strongly in patients with frontal lesions, they are much more sensitive to sequential changes.
When we ask that a sequence be established in a new task, something similar happens, there is a logical sequence, a house is not built starting from the roof, and here again a great difference was observed between healthy individuals and those who had alterations in the frontal region, especially in the dorsolateral prefrontal cortex, indicating the importance of this brain region in sequencing, although we have already seen that other brain regions (parietal) also participate.
Construction inspection
In the context of executive processes, supervision is the evaluation of how one performs a task while performing it, which is not the same as evaluating a task to improve, a process that is performed after the task is completed.
Neuroimaging studies show that supervision tasks are performed in the left prefrontal cortex, although the dorsolateral prefrontal cortex is also activated, which indicates once again that supervision is an executive process.
One aspect that also drew attention was the supervision of errors. Behavioral studies showed that errors are signaled whenever a mismatch is detected between the response that has been given and the correct answer, where the latter is determined by the information that is accumulated after the initial response has been chosen. This process of error monitoring seems to be generated in a structure of the midline of the frontal cortex, possibly the anterior cingulate.
In the next chapter we will develop an exciting topic, that of emotions and cognition, who has not had the sensation of blockade before a moment of anger, "I am so furious that I can not think clearly". If you want to know why, we'll explain it to you.
