Dysexecutive Syndromes Research Paper

Studies of patients with brain damage have suggested a syndrome in which executive control appears to have run amok. In particular, patients with damage to the frontal lobes, the most anterior part of the brain, have problems in controlling and directing their thoughts and actions. Indeed, psychological studies have suggested that the frontal lobes are important for a variety of executive functions, including paying attention, searching for thoughts, retrieving memories, initiating actions, and even controlling emotions (Shimamura 2000, Smith and Jonides 1999). Problems often arise in these patients when they are confronted with multiple sensations or choices and must decide which one to select and which ones to ignore. In this sense, these patients exhibit a ‘dysexecutive syndrome’ (Baddeley 1986).

When confronted with multiple thoughts or choices, patients with frontal lobe damage are easily distracted, unable to focus attention, and have difficulty making plans and decisions. By analogy, consider the kind of control needed to direct traffic in a busy intersection. Cars are entering from all directions, and control must be initiated by preventing some cars from entering the intersection while letting others pass through. Without some control—stop sign, signal, or traffic officer— crashes are likely. Now consider the cars to be neuronal impulses that cross literally billions of intersections. Executive control helps select some impulses while inhibiting others.

1. Paying Attention

Paying attention requires the focusing of one’s thoughts to specific features in the environment. Let’s say you are conversing with someone at a party where many other conversations are occurring at the same time. To carry on your conversation, you must focus your attention on the person with whom you are conversing and attempt to block out or suppress the conversations around you. In the laboratory, a task that has been used to measure attention is the Stroop color-word test. In this task, subjects see a list of color words written in different colored ink (e.g., the word

‘RED’ written in green ink). They are asked to report the ink color of each word and to ignore the word itself. Thus, the task requires subjects to pay attention to ink colors and suppress the natural tendency to read the words. Our ability to suppress reading is not completely successful as it takes much longer to identify the ink color of these words compared to reading color patches (MacLeod 1991).

Patients with frontal lobe damage exhibit particularly long response latencies when asked to name the ink color of stimuli when the stimuli are themselves incongruous color names (Perret 1974). Also, neuroimaging studies (PET, fMRI) suggest that areas in the frontal lobes and areas along the inner or medial surface of the cortex (the anterior cingulate gyrus) are particularly active when individuals perform the Stroop task (Peterson et al. 1999). Thus, based on these findings there is some evidence for a role of the prefrontal cortex in selecting or initiating activation. Damage to this area produces a dysexecutive deficit in the ability to pay attention—that is, control which perceptual features to select and which to suppress (Moscovitch 1994, Shimamura 2000).

2. Searching For Memories

Dysexecutive syndromes include problems in the ability to attend to thoughts and memories just as it includes problems in paying attention to environmental stimuli. For example, take a minute to retrieve all of the words that you can think of that begin with the letter ‘A.’ This task requires you to search your memories and retrieve specific items. Perhaps, you developed a strategy to control what words you retrieved. For example, after trying to come up with just any words that begin with ‘A’ maybe you started to cue yourself with categories, such as foods that being with ‘A’ or animals that begin with ‘A.’ Or maybe you used two-letter cues, such as ‘AB,’ then ‘AC,’ then ‘AD.’ Such strategies are efficient because they facilitate the retrieval of different words and prevent the report of the same words. Patients with frontal lobe damage have difficulty directing their memory searches (Baldo and Shimamura 1998). They may report only five or six different words in a minute and often repeat the same words.

Controlling one’s memories is also important for learning. For example, how would you try to learn the following series of words: car, pear, truck, shirt, banana, hat, airplane, shoe, and apple. Maybe you tried to organize the words by making a story involving the words. Perhaps, you noticed that the words could be grouped by the categories: vehicles, fruits, and clothing. In fact, when learning such word lists, many people group the words in terms of category and then report the words by category saying all of the vehicles first, then fruits, and so on. Controlling our thoughts for efficient learning requires the organization of new material so that it can be retrieved easily (Stuss et al. 1994).

Consider your memory as a library. What if every time you added a new book to your library, you simply threw the book in a pile? After dozens of new books, how easy would it be to retrieve any particular book? An efficient library requires a librarian who catalogs new books and/organizes them on the shelves for efficient retrieval. Learning new knowledge (i.e., adding new books to your library) requires cataloging and organizing new information. A dysexecutive syndrome is akin to a library without a good librarian. Patients with frontal lobe lesions have problems learning new information because they cannot organize their thoughts and put them in an appropriate context. That is, they do not catalog information into meaningful groupings.

3. Making Plans And Selecting Appropriate Responses

A third aspect of executive control concerns the ability to focus on which plans or responses to initiate. If you had many plans for the day, such as meeting friends, shopping, and meals, it is necessary to develop a strategy or scheme for ordering your actions. Some things must be done at specific times (e.g., a lunch date), whereas other actions can be done with less time constraint. Efficient organization of one’s actions requires a kind of control similar to that needed to control one’s memories. Strategies must be developed for efficient use of time and energy. Dysexecutive syndromes lead to poor planning, impulsiveness, and flighty behavior. Patients with frontal lobe lesions often exhibit problems in handling everyday events, because they cannot seem to control and/organize their plans and actions. Instead, they seem to initiate actions that immediately comes to mind, even if the actions may be inappropriate at the time. For example, a patient with severe frontal lobe damage may enter a restaurant, sit next to a stranger having a meal and start eating. Such patients appear to be overcome with immediate needs and motivations rather than controlling and planning actions appropriate for the moment, such as having a host seat you and ordering food from a menu (Miller and Cummings 1999, Milner and Petrides 1984).

4. Controlling Emotions

Finally, dysexecutive syndromes can include problems in controlling one’s emotions. The following passage describes the rather interesting case of Phineas Gage, a railroad foreman who incurred frontal lobe damage following a bizarre accident in which an iron rod penetrated—harpoon-like—through Gage’s skull damaging his frontal lobes (Harlow 1868, MacMillian 2000).

He is fitful, irreverent, indulging at times in the grossest profanity (which was not previously his custom), manifesting but little deference for his fellows, impatient of restraint or advice when it conflicts with his desires, at times pertinaciously obstinate, yet capricious and vacillating, devising many plans of future operation, which are sooner arranged than that are abandoned in turn for others appearing more feasible…In this regard his mind was radically changed, so decidedly that his friends and acquaintances said he was ‘‘no longer Gage’’ (Harlow 1868).

Patients with severe damage to the frontal lobes often fail to control their emotions. They exhibit emotional outbursts, both anger and glee, that are not often socially acceptable, such as physical aggression or inappropriate advances to the opposite sex. In this domain, it appears that most people are able to suppress their emotions when they are not appropriate to elicit. Patients with frontal lobe damage often fail to suppress their emotions.

5. A Board Of Executives

Recent research on human frontal lobes have shed light concerning dysexecutive syndromes. Most of these investigations have centered on the role of the frontal lobes in selecting, monitoring, and controlling mental processes. Indeed, psychological studies of patients with frontal lobe lesions and functional neuroimaging studies of neurologically intact individuals suggest that this brain region is involved in tasks that require many aspects of executive control, such as stimulus selection, working memory, memory retrieval, and set shifting (D’Esposito et al. 1995, Shimamura 2000).

In simplified terms, the prefrontal cortex is your brain’s chief executive—it functions to attend to the environment, ignore irrelevant information, select memories, make decisions, and initiate actions. Without it, thoughts are disorganized, more susceptible to interfering information, and more confused. In actuality, there appears to be several supervisors, each one overseeing a particular mental capacity, such as perceptions, memories, emotions, and action. Thus, the frontal lobes acts more like a governing board of supervisors whose job it is to monitor and control many aspects of mental activity. In the case of Phineas Gage, the supervisor in charge of emotional control was dysfunctional and therefore emotions or feelings were blurted out without regard to the situation or social context. In sum, Phineas was not able to monitor and control the expression of his emotions. Other dysexecutive syndromes appear to affect the attention to perceptions and memories rather than emotions. Interestingly, different parts of the frontal lobes seem to control different aspects of mental function.

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