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Matter of MindA Neurologist's View of Brain-Behavior Relationships$

Kenneth M. Heilman

Print publication date: 2002

Print ISBN-13: 9780195144901

Published to Oxford Scholarship Online: May 2009

DOI: 10.1093/acprof:oso/9780195144901.001.0001

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Conation and Intention

Conation and Intention

Chapter:
(p.199) CHAPTER 9 CONATION AND INTENTION
Source:
Matter of Mind
Author(s):

Kenneth M. Heilman

Publisher:
Oxford University Press
DOI:10.1093/acprof:oso/9780195144901.003.0009

Abstract and Keywords

This chapter discusses intentional systems. Cognitive systems such as language (speech, reading, and writing), spatial skills, and motor skills provide the knowledge of how to interact and operate within the environment, but they do not provide the knowledge of when to interact. There are three intentional, or “when,” decisions a normal person must make: when to act, when to continue acting or persist, and when not to act. The frontal lobes play a critical role in these decisions. The ability to carry out goal-oriented behavior requires both cognitive knowledge (stored primarily in the temporal and parietal lobes) and motivation or biological drives.

Keywords:   initiative, abulia, akinesia, brain, cognitive systems, impersistence, intention

The term conation derives from the Latin word conato which means “attempt.” The word, however, is denned as the initiative to act arising from within oneself. The cognitive systems (e.g., language, spatial and motor skills) provide the person with knowledge of how to operate in the environment, but they do not provide the knowledge of when to interact with it. There are three intentional, or “when,” decisions that a person must make: (1) when to act, (2) when to persist at an act, and (3) when not to act. We will start our discussion of intentional systems by describing people who have lost their initiative.

ABULIA: LOSS OF INITIATIVE

Perhaps the first person to be described with abulia (a = without; bulia = will) was Phineas Gage in John Harlow's 1868 report. In the (p.200) mid-nineteenth century, Gage, a hard-working foreman of a railroad crew, had an accident in which an iron tamping bar, used to place explosives, was propelled by an explosion upward into his skull. The rod entered the left cheek, went through the maxillary sinus on the left side, and impaled the frontal lobes of his brain. It then exited the top of the skull. That Gage survived such an accident was remarkable. It was also remarkable that as a result of this accident he did not become weak and was able to speak normally. He did, however, undergo a dramatic personality change. Before the accident, according to Harlow, Gage had “a well balanced mind. And was looked upon by those who knew him as a shrewd, smart businessman, very energetic and persistent in executing all his plans.” After the accident, Harlow described him as “devising many plans of future operation, which are no sooner arranged than they are abandoned.… In this regard his mind was radically changed, so decidedly that his friends and acquaintances said he was no longer Gage.”

At the end of the nineteenth century, Leonardo Bianchi removed both frontal lobes from dogs and noted that they no longer showed affection for people and no longer groomed, but other changes in conarive behavior may be difficult to detect in dogs. Some late-nineteenth-century and early-twentieth-century investigators thought that injury to the prefrontal lobes did not cause behavioral changes and claimed that the frontal lobes are a “silent” area. Others, however, described many specific behavioral disorders, such as a loss of speech, and changes of mood such as inappropriate jocularity and aggression, but a change in conation was not well appreciated until Karl Kleist reported in 1934 that many of the soldiers who suffered frontal lobe injury in the First World War were apathetic, with a loss of drive and initiative (abulia). It was, however, A.R. Luria who recognized that abulia, or what he called a loss of goal-oriented behavior, was a major factor in the disability associated with frontal lobe injuries.

Although Phineas Gage and the patients reported by Kleist had penetrating wounds of the frontal lobes, abulia can also be caused by closed-head injuries. In the clinic we often see patients who have closed-head trauma after serious automobile accidents and subsequently are unable to resume work. Because they are not weak, numb, blind, or language impaired, people often think that they are merely malingering in order to receive compensation. These people, (p.201) however, may have suffered serious injury to their frontal lobes or to the fibers that enter and exist them. Their problem is not a desire for compensation but rather abulia, a deficit in goal-oriented behavior. In general, these patients, like Phineas Gage cannot follow through on long-term plans. However, when a biological drive state such as hunger develops, people with abulia from frontal lobe injuries who are passive most of the time, become active. They work to satisfy their immediate basic needs, but they do little to make certain that in the future their needs and their families’ needs will be met. When their immediate needs are not met, they easily become frustrated and angry.

Wally Nauta, a Dutch neuroanatomist who worked at MIT, wrote an important paper in 1971 attempting to explain why patients with frontal lobe injuries have trouble with goal-oriented behavior and with self-initiated activities. He noted that information from the outside world is first transmitted to the primary sensory areas in the temporal (auditory), anterior parietal (touch), and occipital (vision) lobes. These primary sensory areas send the information they receive and analyze to their own sensory association areas (see Fig. 4–4). For example, the primary visual cortex, which receives sensory information from the retina, sends it to visual association areas. The visual association cortices analyze this information to determine the shape, color, and movement of whatever is being observed. All these sensory association areas send information to multimodal or synthesizing areas of the temporal and parietal lobes (see Fig. 4–4). These multimodal areas have rich neuronal networks that store memories of the meaning of stimuli and the strategies for solving problems. In people with frontal lobe damage from trauma or disease, these sensory-cognitive systems are usually working, and because they are working, these people are aware of their environment and have retained everyday knowledge. To utilize this knowledge to achieve goals, however, one needs motivation. Knowledge together with motivation leads to goal-oriented behavior.

Motivations or biological drives are present in humans and in more primitive animals such reptiles. These biological drives are mediated by the limbic system and the hypothalamus (Fig. 9–1). Unlike the temporal, occipital, and parietal cortices, which monitor the outside world, the hypothalamus and limbic system monitor the condition of the body. For example, when the blood sugar level becomes (p.202)

                   Conation and Intention

Figure 9–1. Diagram of a midsagittal (cut from front to back) section of the human brain demonstrating the hypothalamus, which monitors body functions. The hypothalamus has reciprocal connections with the frontal lobes and portions of the limbic system, including the cingulate gyms and the amygdala.

too low, the animal gets hungry and searches for and eats food. When the blood salt level become too high, the animal becomes thirsty and searches for and drinks water.

Patients with frontal lobe injuries have an intact hypothalamus and limbic system, areas that mediate biological drives (e.g., thirst and hunger) and emotions (e.g., fear and anger). Therefore, when they develop a need, they attempt to satisfy it. The hypothalamus and limbic system (which includes the cingulate gyrus and amygdala) send a large number of projections to the frontal lobes (Fig. 9–1). The posterior (temporal-parietal) multimodal sensory areas also send large numbers of projections to the frontal lobes. According to Wally Nauta, the frontal lobe networks fuse biological drives and impulses with the knowledge of how to satisfy them. This fusion leads to the development of goal-oriented behavior, or conation. The frontal lobes project to the motor systems, enabling motivational states to initiate overt behavior.

People with intact frontal lobes are also able to resist immediate biological drives in order to satisfy long-term goals, but when the frontal lobes are damaged, the motivation to reach these goals is lost, although the biological drives and cognitive knowledge remain intact. A farmer we examined had suffered a frontal lobe injury in a car accident. When he became hungry, he wanted food (p.203) immediately. If he did not get food, he became abusive toward his wife. He also knew that if he wanted food in the winter he would have to plow and plant in the spring, but instead he sat at home and watched television.

The ability to pursue long-term goals and to suppress biological drives is one of the major factors underlying success in any profession. Whereas knowledge, or cognition, is easy to measure, conation is not. One of the most difficult jobs I’ve ever had was being a member of the medical school's admissions committee. Committee members typically use four criteria to judge applicants: college grades, scores on the Medical College Aptitude Tests (MCATs), extracurricular activities or special talents, and student performance during the interview. Almost every applicant I interviewed had a nearly perfect grade point average (3.8 to 4.0) and performed well on the MCATs. It seemed to me that a more important factor for success in medicine or other careers is the capacity for goal-oriented behavior. Because the frontal lobes are the critical part of the brain for this function, I (colloquially) call this capacity for goal-oriented behavior frontal intelligence. Will the students/physicians be willing to stay up all night to take care of a critically ill patient? Will selfish goals be their main source of motivation or will they work for the benefit of their patients and community? I found my work on the admissions committee difficult because I was unsure of how to judge frontal intelligence.

It is unclear if frontal intelligence is learned or biologically endowed. Although intellectual (e.g., language and math) intelligence is partly endowed, keeping children in enriched environments helps develop this intelligence. If frontal intelligence is learned, how do we foster it? When our children were young, my wife and I had a disagreement that, to my mind, has never been resolved. She is a speech pathologist and works with children who have language (reading and speech) disabilities. She believes in operant techniques. Thus, for example, when a child performs well, she or he is rewarded. Because she has used this operant technique at school and has found that it succeeds in changing or promoting certain behaviors, she also wanted to use it at home with our children. I was against the extensive use of this technique because I was concerned about fostering frontal intelligence.

It is unclear how frontal intelligence develops. We know that learning causes the brain to change (plasticity) and that learning (p.204) can take place throughout life, but certain skills are best learned during certain stages of development. A child who moves to the United States before puberty will have little if any foreign accent, but for one who arrives after age 16, there is a high probability that a foreign accent will be permanent. Henry Kissinger is a good example of this principle. If a child is blind because of corneal clouding and remains blind for several years, when visual acuity is restored with a corneal transplant, the child may still never have useful vision. These observations suggest that children have to learn certain things before they reach critical ages. The frontal lobes are one of the last areas of the brain to mature and may not be fully mature until the person reaches the twenties. This may be why teenagers get into so much trouble. Their increase in sex hormone production creates new, strong drives with a desire for immediate gratification, but with immature frontal lobes they have poor conation. These biological drives and the desires they engender, rather than long-term goals, often control the teenager's behavior. Because children often do not have good conation, educators and parents often successfully use operant techniques to control behavior.

Operant techniques, or behaviorism, were made famous by the Harvard psychologist B.F. Skinner. I first learned about behaviorism when I was in college. Although I was a chemistry major, I took an introductory course in psychology. At the University of Virginia in 1958, the Department of Psychology was strongly influenced by behaviorism and the works of Skinner. Skinner thought that in order to modify behavior, it is necessary to reinforce desired behaviors and avoid reinforcing behaviors to be terminated. We were required to read several books by Skinner, including Walden Two and Of Human Science and Behavior. These books presented his theories of behaviorism and how the use of operant conditioning principles may make the world a better place. I thought these books were oversimplified and did not deal with several important behavioral issues. After reading them, I asked my psychology professor, “What about the brain?” He replied, “In order to understand behavior, you do not need to know anything about the brain.” I also asked, “Based on behavior principles, how do we decide what we should do in the future?” He said, ‘Your decisions will be based upon how you were rewarded in the past.” I was not happy with either of these answers, and based in part, on this class, I decided that I might want to study the brain.

(p.205) Shortly after joining the faculty at the University of Florida College of Medicine, I learned that B.F. Skinner was coming to Gainesville to give a lecture and I decided to attend. He gave one of the most depressing lectures I have ever heard, stating that we humans are doomed because we can learn only by behaving. When a behavior is reinforced we perform it again, but if it is not reinforced we will be less likely to perform it again, and eventually the behavior will be extinguished. According to Skinner, there is no hope of avoiding a thermonuclear war because the behaviors that would unleash this disaster could not be extinguished until after the behavior became manifest. When listening to this lecture, I thought it was unfortunate that Skinner had not learned more about the brain and how it controls behavior. If he had learned about frontal lobe functions, he would have known that the frontal lobe systems mediate goal-oriented behavior, and this behavior predicate current behavior based on future outcomes. People with intact conative (frontal) systems may not start a thermonuclear war because their knowledge of the outcome may constrain behavior (as it so far has). This is one example of why the development of conative systems is critical, and one possible consequence of using operant techniques excessively in children may be the failure to develop frontal intelligence. To illustrate how these operant techniques may impede conative control systems, consider the story of Solly, the Jewish tailor.

In 1939, Solly left Poland with his family because of Hitler, came to the United States and opened a little shop in a suburb of Indianapolis. Unfortunately, unknown to him, this suburb had a very strong pro-Nazi German-American Association and was virulently anti-Semitic. The members of this Association hoped that his business would fail and that Solly would leave town for New York, where most Jews lived, but because Solly was an excellent tailor and most of the townspeople were not anti-Semitic, his business thrived. The association ordered their youth organization, modeled after Hitler's, to demonstrate outside the tailor's shop. When he looked out of his shop window one summer morning, Solly saw ten teenage boys marching in front of it carrying terrible signs and yelling horrible words: “JEW-BASTARD LEAVE TOWN.” “NO HOME FOR KIKES.” “CHRIST KILLER.”

After looking at the signs for a few minutes, Solly went to his cash register. He took out ten $5 bills, walked outside, and handed one bill to each of boy, saying, “Good job.” When the boys returned (p.206) to the German-American Association clubhouse, their leader asked how it went. The oldest boy replied, “Fine, but after we marched around for a while, that crazy old Jew came out and gave each of us $5.” The leader said, “You and your friends need to march around each day until that kike leaves town.”

The next day, the boys took their signs and again marched outside of the tailor's shop. This time Solly took out ten $1 bills and gave one to each boy. The following day he gave them 50 cents and the day after that 25 cents. He continued to reduce the payment until he gave each boy just a nickel. The next day, the boys did not march. When the leader of die association saw them sitting around the clubhouse, he asked, “Why aren’t you harassing that kike?” The oldest boy said, “Hell, it's not worth marching around a few hours for only a nickel.”

Although in this story an operant technique did reduce goal-oriented behavior, it remains unclear if the extensive use of this behavior modification system with children inhibits the development of frontal intelligence. More research is needed.

Akinesia: Inability to Move

Abulia can become so severe that even in the absence of weakness, some patients are unwilling but not unable to move. Their major problem appears to be an inability to get started by themselves. This condition is called akinesia (a = without; kinesia = movement). One of the most dramatic cases of akinesia I have ever seen was that of Thomas Taylor, a 58-year-old Baptist minister from Deland, Florida. First, Mr. Taylor developed abulia, but as his disease progressed he became akinetic. His family brought him to see me in 1971 because all he did every day after his family got him out of bed was to sit on the couch. Formerly, when sitting there he turned on the television, but eventually even this action stopped. Although he had once loved to talk, now he talked only when someone asked him a question. When he responded, he usually gave a one-word answer. Two or three years before seeing me he had been a meticulous, independent, and active man, but by 1971, according to his wife, he did not even get up to go to the bathroom and often urinated in his pants. He bathed, shaved, and changed his clothing only when his wife strongly encouraged him.

(p.207) I asked his wife how this condition began. She said that her husband had been a hard-working man. Although the members of the church wanted to pay him, he thought it was wrong for a preacher to be paid—a conflict of interest—so he continued working, drilling wells for water, except when someone needed help or on Sundays. The first symptom his wife noticed was that he started being late for appointments. He usually gave a new sermon each week, but then he started repeating some of his sermons. In the last month he preached, he gave the same sermon three Sundays in a row.

While Mr. Taylor listened to his wife give me this history, he was shaking his head. I asked him if her story was wrong and he said, “No, it is correct.” When I asked why he gave the same sermon repeatedly, he replied, “If they are dumb enough to stay and listen to the same sermon, they deserve what they get.” On hearing these words, a few tears came to his wife's eyes. “Dr. Heilman you cannot believe how much this man has changed. Three or four years ago, I could never imagine him saying anything like that.”

On neurological examination, Mr. Taylor showed many signs of frontal-subcortical dysfunction. Some frontal-subcortical behaviors are primitive reflexes that one sees in the infant, such as a hand grasp, a sucking response, and rooting. Normally, as the infant's frontal lobe matures, these reflexes are inhibited, but with damage to the frontal lobe they might reappear. When Mr. Taylor attempted to stand, he had a tendency to fall backward (retropulse). When I held him and had him walk he took small steps, another sign of frontal lobe dysfunction. The history of slowly progressive frontal lobe dysfunction suggested one of four conditions: a tumor, a chronic infection, a degenerative disease, or hydrocephalus. In 1971 there were no CT or MRI scans. Instead we obtained an arteriogram, injecting dye into the arteries that supply the brain with blood. This revealed that Mr. Taylor had a tumor pressing on the middle part of both the right and left frontal lobes. We described this finding to him and his wife and recommended that the neurosurgeons remove the tumor. Fortunately, it was a meningioma, a benign tumor of the membranes that cover the brain, and the neurosurgeons were able to remove it completely. I saw Mr. Taylor once at a follow-up visit, and he showed dramatic improvement. He was not preaching but was teaching at Sunday school, caring for himself, and making plans to start work again.

(p.208) The type of akinesia that Mr. Taylor demonstrated, in which a person remains inactive unless externally prompted, is often associated with bilateral medial frontal lobe lesions (Fig. 9–2). This area of the frontal lobes appears to contain the person's “starting engine,” and when this engine fails, as it did in Mr. Taylor, in order to start an activity the person needs to be prompted by someone else. This area of the frontal lobe sends a large number of projections to the motor system, and it is important in activating the motor neurons and hence behavior.

In addition to the anterior and medial portions of the frontal lobes, other regions of the brain that are important in activating the motor cortex. Deep in each hemisphere lie structures called the basal ganglia (Fig. 9–3), which receive information from the cortex and send it by an indirect route through the thalamus and back to the cortex. The exact functions of these cortical—basal ganglia—thalamic-cortical circuits are still unknown, but we do know that when they are not working properly, in conditions such as Parkinson's disease, patients have akinesia, or trouble moving. Many people think diat patients with Parkinson's disease have trouble moving because they are stiff. While it is true that they are stiff, it is not stiffness that is causing their problem in initiating movements. Their problem is that they cannot will themselves to move, though an external stimulus can help them initiate activity. Before successful drug treatments for Parkinson's disease were available, many patients were

                   Conation and Intention

Figure 9–2. Dorsal view of the brain demonstrating a lesion of the medial frontal lobes found in Mr. Taylor, the patient with akinesia (inertia).

(p.209)
                   Conation and Intention

Figure 9–3. A coronal section is a cut through the brain from the top to bottom. This section allows one to see what is under the cortex. This diagram of a coronal section through the human cerebral hemispheres demonstrates the cortex, the basal ganglia (putamen, globus pallidus, caudate, substantia nigra), the ventricles (which contain spinal fluid), the thalamus, and the connections between these areas.

unable to get out of their bed or chair for months or years unless someone helped them. Yet in several reports of fires at nursing homes, these apparently immobile patients were often among the first to leave the burning building. Although in the absence of a relevant stimulus the frontal lobe-basal ganglia systems are important for activating the motor system, the posteriorly located sensory (p.210) and sensory association systems can also access and activate the motor systems. Disorders of the basal ganglia such as Parkinson's disease and frontal lobe injury cause failures of self-initiation, but sensory stimuli such as seeing a fire, feeling the heat, or smelling the smoke directly activate the motor systems even when the frontal-basal ganglia systems are impaired.

IMPERSISTENCE

Mr. Taylor, the Baptist minister with abulia and akinesia, had a third sign of defective conation. As part of my examination, I wanted to see if Mr. Taylor's sensation was normal. I tested proprioception by asking him if he could feel me moving his big toe. I said, “Mr. Taylor, I want you to close your eyes until I tell you to open them. I am going to move your big toe either up or down. After I have moved it, you tell me which way I moved it.” I watched as Mr. Taylor closed his eyes; then I looked down and moved his big toe up. He said, “Up.” But when I looked up at him, his eyes were open. I said to him again, “Please close your eyes and keep them closed until I tell you to open them.” As soon as I touched his big toe, however, he again opened his eyes. Eventually, I had to blindfold him. Mr. Taylor's inability to keep his eyes closed is called impersistence. I also tested his ability to persist in keeping his mouth open; he was unable to keep it open for more than a few seconds.

Patients with motor impersistence may also have impersistence when performing other activities. Mrs. Taylor told me that she thought one of the reasons her husband gave the same sermon more than once was that when he tried to write a new sermon, he worked on it for only a few minutes and then quit. She was describing a form of cognitive impersistence.

Impersistence is also a failure of the “when” system. Mr. Taylor closed his eyes because I told him to do so. My command was an external stimulus. In the absence of repeated external stimuli such as repeated commands, however, he could not continue this motor activity. Andy Kertesz, at the University of Western Ontario, demonstrated that people with impersistence most often have damage to the frontal circuits.

(p.211) ENVIRONMENTAL DEPENDENCY

Although it is difficult for patients with frontal lobe disease or injury to initiate behaviors themselves, they will often become active when someone else encourages them to act. The behavior of these patients appears to be entirely controlled by the external world. During psychological testing of Mr. Taylor, I put a pen and paper on a table in front of him (so that he could copy intersecting pentagons), but before I showed him the picture I wanted him to copy or gave him any instructions, he picked up the pen and started writing his name. Francois Lhermitte, described many patients with similar behaviors. One patient was a nurse with frontal lobe dysfunction. When he put a syringe with needle on a table, she gave him an injection. Lehrmitte called this form of environmental dependency utilization behavior.

There are other methods of testing patients for environmental dependency. In performing an examination, a neurologist will tell die patient to keep his or her hand open while the neurologist slides the index and middle fingers down the patients’ palm. Without instructions to close their hand or to grasp the examiner's fingers, some patients with injury to the frontal lobes or subcortical structures will often hold or even gently squeeze the neurologist's fingers. I often say to patients, “Please do not hold my hand,” but after a few seconds, they will hold my hand again. Sometimes, if this grasp reflex is strong, the examiner does not even have to touch the patient's hand. Merely seeing the examiner's hand, especially when it is moving, will cause the patient to reach for it and attempt to hold it. The patient's hands are not the only body part that can inappropriately approach the examiner or other stimuli. Sometimes touching diese patients’ lips or cheeks will cause diem to move their head and mouth so that they appear to want to place the examiner's hand in their mouth. This is called the rooting reflex. These same primitive reflexes can be observed in infants, and it is thought that they are important for feeding and holding on to the mother. Like these patients, infants do not have fully functioning frontal lobes. Many of these approach and environmentally dependent behaviors are seen in patients with abulia.

Derek Denny-Brown suggested that as die brain develops, the organism learns specific adaptive strategies to use with specific (p.212) stimuli. Most of this cognitive knowledge is stored in the temporal and parietal lobes. Normally, when a person confronts an environmental stimulus, the way he or she deals with it should depend on a learned strategy. According to Denny-Brown, the development of the frontal lobes allows a person to avoid responding automatically to a stimulus (environmental dependency) and instead allows the learned strategy to dictate behavior. In Denny-Brown's view, the frontal lobes mediate avoidance behaviors and the temporal-parietal lobes mediate approach behaviors. With injury to the frontal lobes, there is a propensity both to respond inappropriately to stimuli and to have environmental stimuli, rather than long-term goals, control behavior. The frontal lobes are one of the last parts of the brain to mature. That is why young children often act when they know they should not have acted. The game “Simon Says” is a good test of frontal lobe function in children. In this game, the call to action is the phrase, “Simon says.” But children will often follow commands not preceded by this term.

A.R. Luria devised a simple bedside test of Denny-Brown's hypothesis. The examiner tells the patient to make a fist with one hand, and when the examiner holds up one finger, the patient is instructed to hold up two fingers. When the examiner holds up two fingers, the patient is to hold up one finger. After the patient has learned these two simple rules, the examiner usually performs ten trials randomly, showing the patient either one or two fingers. Even normal subjects can sometimes make errors, but patients with impaired frontal lobe function will often first hold up the same number of fingers as the examiner and then make the appropriate correction. In another test of environmental dependancy, we have patients put their hands on their lap. We then tell them that when we touch their left hand, they are to raise the right hand, and when we touch their right hand, they are to raise the left hand. Patients with frontal lobe dysfunction often raise first the hand that was touched and then the other hand. When these patients are questioned about the instructions or correct their errors, it is apparent that they know the cognitive strategy. These patients’ test performance supports Denny-Brown's hypothesis that with frontal lobe injury it is the stimulus rather than the cognitive goal that controls behavior.

(p.213) RIGHT-LEFT ASYMMETRIES OF CONATION OR INTENTION

Although defective response inhibition (a form of environmental dependency) is most frequently associated with bilateral injuries to the frontal lobe circuits, milder symptoms are associated with injuries to the right hemisphere's frontal lobe alone. Similarly, most severe cases of abulia and akinesia also result from injuries to both sides of the dorsolateral or medial frontal lobes, but milder forms of abulia and akinesia are also more likely to be associated with right than left hemisphere injuries. Andy Kertesz reported that damage to both hemispheres can cause the most severe impersistence, but when the injury is restricted to one hemisphere, impersistence is more commonly associated with right than with left hemisphere injury.

In the past 25 years, many people have theorized about the duality of the right and left hemispheres. For example, the left hemisphere has been called the verbal hemisphere and the right the spatial hemisphere. Others call the left hemisphere the propositional hemisphere and the right the emotional hemisphere. Although many theorists have warned us about these simple dichotomies, Marcel Kins bourne suggested that it is fortunate that humans, who love dichotomies, do have two hemispheres. Based on the observation that akinesia, impersistence, and defective response inhibition are more frequently associated with right than with left hemisphere damage, perhaps I will join the dichotomists by suggesting that whereas the left hemisphere is dominant for mediating “how” activities, including how to perform learned skilled movements, how to speak and understand, and how to read and write, the right hemisphere mediates “when” decisions including when to move or act, when to persist at an action, and when not to act. Unfortunately, we still do not fully understand the structural basis for these asymmetries, but “when” decisions are based on goals, and goals, as Wally Nauta suggested, are related to biological drives. Biological drives are mediated by portions of the limbic system, and Albert Galaburda demonstrated in human brains that thesystem has more connections with the right than with the left hemisphere.

(p.214) SUMMARY

Cognitive systems such as language (speech, reading, writing), spatial skills, and motor skills provide the knowledge of how to interact and operate within the environment, but they do not provide the knowledge of when to interact. There are three intentional, or “when,” decisions a normal person must make: when to act, when to continue acting or persist, and when not to act. The frontal lobes, especially on the right, play a critical role in these decisions. The ability to carry out goal-oriented behavior requires both cognitive knowledge (stored primarily in the temporal and parietal lobes) and motivation or biological drives. Biological drives such as thirst and hunger, as well as emotions such as anger and fear, are mediated by the limbic system, which includes the hypothalamus and amygdala. The frontal lobe fuses these biological drives with the knowledge of how to satisfy them. Through the frontal lobes’ connections to the motor system, this fused knowledge leads to goal-oriented behaviors.

Selected Readings

Damasio, A.R. (1994) DescartesError: Emotion, reason and the human brain, G.P. Putnam's Sons, New York.

Damasio, A.R. Andeson, S.W. (1993) The frontal lobes. In Clinical Neuropsychology. (Ed.) Heilman, K.M., and Valenstein, E., Oxford University Press, New York, pp. 409-460.

Levin, H.S., Eisenberg, H.M., Benton, A.L. (Eds.). (1991) Frontallobe function and dysfunction, Oxford University Press, New York.

Nauta, W.S., (1971) The problem with the frontal lobe: a Reinter pretation. Psychiatr. Res. 8:167-187.

Stuss, D.T., Benson D.F. (1986) The frontal lobes, Raven Press, New York.