The frontal lobes are aptly named because they are located at the front of the cerebral cortex just behind the eyes and forehead. The frontal lobes make up a very large part of the cerebral cortex in humans — about 20% or more. Since the late 18oos, brain researchers have known that the frontal lobes are important for voluntary movements of bodily muscles; but, for almost a century, they did not know much more. For one thing, they found that many intellectual functions remained relatively intact even after extensive damage to the frontal lobes. People who experienced strokes[∂] that caused significant damage to the frontal lobes, for example, often received average to above-average scores on intelligence tests. Furthermore, people who had prefrontal "lobotomies" (no longer performed) — a procedure that destroyed connections between parts of the frontal lobes and the rest of the brain — often functioned adequately in many ways. In summarizing the effects of frontal-lobe damage, Howard Gardner (1974) stated that the “frontal-lobe patient”:

may completely fool the unsuspecting psychologist or the physician, who may conclude on the basis of high scores and appropriate answers that he is dealing with a competent individual. That is because the frontal-lobe patient superficially retains the major cognitive, intellectual, and sensory capacities tapped by psychological tests. His deficiencies [exist] in those very judgmental capacities to plan ahead, to assess the consequences of actions, to evaluate alternatives, to conceive of a situation in multiple ways, to detect subtle social and emotional cues, which are the keynotes of the highest human functions, indeed those which, according to [the Russian neurologist, A. R.] Luria, “make a person human.” (p. 433)

In other words, damage to the frontal lobes results in important (though often subtle) cognitive, emotional, and/or behavioral changes that often are reflected in personality changes. It may be difficult for one who doesn't know the patient well to state precisely what is wrong. But for those who knew the patient both before and after frontal-lobe injuries, the patient may appear less motivated, more impulsive, and less able to organize his or her thoughts. Research preformed from the 1970s to the present day has shown that the frontal lobes have three major functions:

• Initiating Movements. Activity in an area at the rear of the frontal lobes is essential for initiating movements in the skeletal muscles[∂].
• Language Production. Activity in the left frontal lobe of most people is necessary for producing spoken, written, or signed language.
• Working Memory. Activity in the frontal lobes is essential for attending to information, organizing it, and using it to make plans, solve problems, etc (discussed in Section 4-8).

Initiating Movements

There is a strip of cells at the back of the frontal lobes that, when electrically stimulated, produces movements of the skeletal muscles — the muscles attached to the skeleton of the body (also often referred to as "voluntary muscles" because they are involved in those movements that we we can consciously control). This area is referred to as the primary motor cortex. As can be seen in Figure 1, the movement of each part of the body is controlled by activity in specific areas of the motor cortex. Movement of the tongue, for example, is controlled by a part of the motor cortex located near the part that controls swallowing; and the part controlling the movement of the neck is controlled by a part of the motor cortex that is located near the part controlling the movement of the eyes and eyelids. The degree to which a part of the body can be moved in highly complex and coordinated sequences of behaviors is dependent upon the amount of the motor cortex reserved for the movement of that body part. For example, our thumbs and fingers are able to engage in many highly coordinated movements and, as you can see in Figure 1, a large part of the motor cortex controls movements of the hands and fingers. The muscles in our toes, however, are not capable of performing anything but simple movements; and Figure 1 shows that little of the motor cortex is set aside for moving these muscles.

Figure 1. The primary motor cortex and the bodily areas affected by activity in each part
(the picture appears at this link)

As with vision and touch, the neural pathways controlling movement cross over, which means that movements on the left side of the body are controlled by activity on the right side of the motor cortex, whereas movements on the right side of the body are controlled by activity on the left side of the motor cortex. Paralysis occurs when any part of the motor cortex is damaged. When this occurs, paralysis develops on the side of the body opposite to the damage.

Broca's Area

A central concept in the approach used by cognitive psychologists is information processing (later in this course, you will learn much more about cognitive psychology). The term is borrowed from computer terminology and, with respect to sensation and perception, information processing refers to the mental processes involved in the analysis of sensory "data" and the conversion of the results into a form that can be used in other, often more complex, mental processes.This may make little sense to you now, so the most important thing to know is that information processing refers mostly to those mental processes involved in knowing the world around us — in perceiving objects, people, etc., and then figuring out whether we need to respond to any of these things; and, if we do need to respond, figuring out how best to respond. Information processing also involves responding involuntarily to the world around us, such as crying when we realize (through information processing) that something very sad has occurred.

The frontal lobes are essential for complex information processing using "input" from many other areas of the brain (see Section 4-8). Clinical research suggests that, once sensory information has been received and recognized in the sensory areas of the cortex, the processed information is sent to the frontal lobes, which organizes and processes it further. One example of this is seen in the mental processing that occurs in Broca's Area (see Figure 2: this is the same illustration you saw in Section 4-6). Broca’s area is in the left frontal lobe of most people, and is involved in comprehending and producing language, whether spoken or written. When Broca’s area is damaged, people experience language difficulties called Broca's aphasia (named after the neurologist who first described it in 1861, Paul Broca). People with Broca’s aphasia typically have paralysis on the right side of the body because Broca’s area is located next to the left motor cortex. Thus, when Broca’s area is damaged, the motor cortex also is damaged in many cases, thereby producing paralysis on the opposite side of the body (usually the right side).

Figure 2. Two language areas in the left hemisphere of the cerebral cortex
(from Kandel, Schwartz, & Jessell, 1995, p. 642)

Gardner (1974) described a patient with Broca's aphasia, whom he called "David Ford." David was in his late 30s when interviewed by Gardner, and had been a radio operator in the Coast Guard until he suffered a stroke that put an end to his career. After the stroke, David experienced a great deal of difficulty producing written and spoken language. When he was able to produce words, he did so in a halting manner and made many mistakes. These problems are evident in Gardner's description of his initial interview with David soon after he entered the hospital:

I asked Mr. Ford about his work before he entered the hospital.
“I’m a sig. . . no . . . man . . . uh, well, . . . again.” These words were emitted slowly, and with great effort. The sounds were not clearly articulated; each syllable was uttered harshly, explosively, in a throaty voice. With practice, it was possible to understand him, but at first I encountered considerable difficulty in this.
“Let me help you,” I interjected. “You were a signal . . .”
“A sig-nal man . . . right,” Ford completed my phrase triumphantly.
“Were you in the Coast Guard?”
“No, er, yes, yes . . . ship . . . Massachu . . . chusetts . . . Coastguard . . . years.” He raised his hands twice, indicating the number “nineteen.”
“Oh, you were in the Coast Guard for nineteen years.”
“Oh . . . boy . . . right . . .,” he replied.
“Why are you in the hospital, Mr Ford?”
Ford looked at me a bit strangely, as if to say, Isn’t it patently obvious? He pointed to his paralyzed arm and said, “Arm no good,” then to his mouth and said, “Speech . . . can’t say . . . talk, you see.”
“What happened to make you lose your speech?”
“Head, fall, Jesus Christ, me no good, str, str . . . oh Jesus . . . stroke.”
“I see. Could you tell me, Mr. Ford, what you’ve been doing in the hospital?”
“Yes, sure. Me go, er, uh, P.T. none o’cot, speech . . . two times . . . read . . . wr . . . ripe, er, rike, er, write . . . practice . . . get-ting better.”
“And have you been going home on weekends?”
“Why, yes . . . Thursday, er, er, er, no, er, Friday . . . Bar-ba-ra . . . wife . . . and, oh, car . . . drive . . . purnpike . . . you know . . . rest and . . . tee-vee.”
“Are you able to understand everything on television?”
“oh, yes, yes . . . well . . . al-most.” Ford grinned a bit. (pp. 60-61)

It is obvious that David had a great deal of trouble expressing himself in this conversation. Furthermore, unlike people with Wernicke's aphasia, people with Broca’s aphasia realize that they are having difficulty expressing themselves, and often become distressed about this, as did David in the passage quoted above. People suffering from Broca's ’s aphasia tend to have two major language impairments:

• Difficulty producing words, whether spoken or written.
• Difficulty comprehending words, especially "grammatical words."

Difficulty producing words. People with Broca’s aphasia, if they speak at all, tend to speak slowly and with poor articulation. In addition, they tend to leave out many words and may produce neologisms that sound similar to the correct ones, such as David’s use of “purnpike” and “o’cot.” He was able to speak only a few words at a time and never expressed a complete and grammatically correct sentence. In fact, he often had trouble getting past the first or second word, and would need to start over again. Certain phrases that David probably had used often before his stroke (such as “Jesus Christ”) were said quickly and clearly; but he had enormous difficulty with almost all other words. In general, people suffering from Broca’s aphasia experience severe impairments in the following: speaking spontaneously (saying something that is not a response to something said by another person) and repetition (repeating a word after someone else has said it). Nevertheless, they often have little trouble understanding what others are saying as long as the sentences are simply structured. This brings us to the second major impairment of Broca's aphasia.

Difficulty comprehending words. People with Broca's aphasia typically have no trouble understanding nouns and verbs, but they often have difficulty comprehending "grammatical words" — words other than nouns and verbs that allow us to construct meaningful sentences (Geschwind, 1974; Goodglass & Geschwind, 1976). These include, for example, the following classes of words:

• prepositions, such as ‘by’, ‘in’, ‘on’;
• articles, such as ‘a’, ‘the’;
• conjunctions, such as ‘and’, ‘or’, ‘but’;
• helping verbs, such as ‘is’ or ‘be’;
• pronouns, such as ‘he’, she’, ‘it’;
• endings, such as past tenses, possessives, and plurals.

People with Broca’s aphasia often omit and seem not to understand these grammatical words. Thus, they have great difficulty understanding a sentence such as:“The ball was hit by Tommy into the left-field bleachers.” The five underlined words are grammatical words, whereas the words most likely to be understood by a Broca’s patient would be the five nouns and verbs (ball, hit, Tommy, left-field, bleachers). If the sentence had been structured differently so that there were fewer grammatical words, most Broca’s patients would have little difficulty understanding its meaning: “Tommy hit the ball into the left-field bleachers.” In this sentence, there are only three grammatical words and five nouns and verbs, thereby making this sentence much easier to process.

Portions of the brain other than Broca's and Wernicke's Areas also are involved in the use and comprehension of language. Because these other areas may be able to help compensate for damage to Broca's or Wernicke's Areas, people who have damage to only one or the other area generally do not show fully the difficulties described in this and the previous section. The degree of impairment depends on the amount of damage to Broca's or Wernicke's Areas, and whether or not other language areas can compensate.

There are other types of aphasia that seem to be associated with damage to various areas of the brain — areas that may not even be in the cerebral cortex. In short, language use and comprehension is linked to activity in many different areas of the brain that are spread throughout the cortex, limbic system, and brain stem (cerebellum).

Study Questions for Section 4-7

1. The frontal lobes make up about how much of the cerebral cortex?
2. Why had it been so difficult to understand the major functions of the frontal lobes before about 1975?
3. What are the three major functions of the frontal lobes?
4. Which part of the frontal lobes controls movement of the skeletal muscles?
5. What happens if the primary motor cortex in the right hemisphere is damaged?
6. According to Figure 1, if the part of the motor cortex that controls movements of the eyeball and eyelid is damaged, what other movements might a person have difficulty performing?
7. What does Broca's Area do?
8. How is Broca's aphasia similar to, and different from, Wernicke's aphasia?
9. How might difficulties in comprehending grammatical words cause the reduced ability of Broca's patients to produce (and understand) language?
10. If a person has no damage to either Broca's or Wernicke's Areas, can that person still have aphasia? Why or why not?

Go to Quiz 4-7 questions

Go to Readings Section 4-8