Executive Function Case File

Executive Function Case File

EUGENE C.TOY, MD, RAHUL JANDIAL, MD, PhD, EVAN YALE SNYDER, MD, PhD, MARTIN T. PAUKERT, MD

CASE 47

A 23-year-old male is brought into the clinic by his mother. She states he has not been acting like himself ever since he received a head injury in the war. Previously a polite and easygoing individual, she says he is now ill-tempered and makes frequent inappropriate comments. As a result the patient has not been able to hold down a steady job, and has alienated many of his friends. She says he has noticed simple tasks to be more frustrating lately, but otherwise does not think he has changed since his injury. On examination, the patient has a scar over his right forehead. His neurological examination is normal with the exception of perseveration on his cerebellar function testing.

• What area of the brain has most likely been injured, leading to this patient’s symptoms?
• Why has the patient experienced personality changes?
• How will the patient respond when presented with a novel task?

ANSWERS TO CASE 47: EXECUTIVE FUNCTION

Summary: A 23-year-old, posttraumatic brain injury patient presents with symptoms of disinhibition and personality change.

• Region of the brain most likely injured: The frontal lobes, the site of executive cognitive function, are the most likely area to have been damaged. The frontal lobes are commonly involved in traumatic brain injury (TBI), owing to location and size. Likewise, the sphenoid wing and orbit of the skull damage the brain when applied with force to the tissue.
• Most likely cause of the patient’s symptoms: The frontal lobes are responsible for executive cognitive function, and are considered the source of personality and emotional control. Patients with dysexecutive syndrome have difficulty in social settings requiring intricate thought processes and intuitive nuances.
• When the patient is presented with a novel task: The executive system facilitates learning, making actions and problem solving less effortful with repetition. The frontal lobes also function in conceptualization of abstract problems and following through with a complex, predetermined plan. Unable to adapt to novel situations and interactions, combined with a disinhibition of emotional control and social norms, patients with frontal lobe damage may become easily enraged.

CLINICAL CORRELATION

The symptoms this patient exhibits suggests that the patient has a frontal lobe lesion. Lesions in the frontal lobes are known to cause aggressiveness in patients (ie, Phineas Gage phenomenon) and hinder the patient’s ability to carry out executive functions. These functions include behaviors such as planning multistep tasks, the capacity for quick switching to the appropriate mental mode, the ability to withstand distractions or internal urges, anticipation, logical analysis, working memory, multitasking, and decision making.

APPROACH TO EXECUTIVE FUNCTION

Objectives

1. Be able to define the role of the frontal lobes in higher cognitive function.
2. Understand the common symptoms associated with frontal lobe lesions and traumatic brain injury.
3. Be familiar with the mechanisms for testing executive function.

Definitions

Perseveration: Persistent repetition of an activity, word, phrase, or movement without any apparent stimulus for it.

Coup/contrecoup: Contusions both at the site (coup) of impact and on the opposite side (contrecoup) of the brain.

Thurstone (letter fluency, word generation) test: Ask the patient to generate as many words as possible beginning with the letter F in 1 minute. A normal score for a native English speaker with at least a high school education is at least 8 words.

Serial 7s: Counting down from 100 by 7s. Tests concentration and memory. Spelling the word world backward commonly is used as a substitute for patients who cannot perform calculations of 7s.

Digit span: Also a measure of attention and concentration. A normal span is seven digits forward and five backward. An abnormal digit span is the most common neuropsychological deficit in patients with head injury.

DISCUSSION

The frontal lobe is an area in the brain of mammals located at the front of each cerebral hemisphere, frontal lobes are positioned anterior to the parietal lobes. The temporal lobes are located beneath and behind the frontal lobes. In the human brain, the precentral gyrus and the related cortical tissue that folds into the central sulcus comprise the primary motor cortex, which controls voluntary movements of specific body parts associated with areas of the gyrus. The frontal lobes have been found to play a part in impulse control, judgment, language production, working memory, motor function, sexual behavior, socialization, and spontaneity. The frontal lobes assist in planning, coordinating, controlling, and executing behavior. People who have damaged frontal lobes may experience problems with these aspects of cognitive function, being at times impulsive; impaired in their ability to plan and execute complex sequences of actions; perhaps persisting with one course of action or pattern of behavior when a change would be appropriate.

The executive functions of the frontal lobe involve abstract thinking, rule acquisition, problem solving, planning, cognitive flexibility, selecting relevant sensory information, initiating behavior, monitoring behavior via judgment and impulse control, motor function, executive memory, language, sexual behavior, and decision making. It allows for adaptation to new environments and the acquisition of new skills or manners of thinking. This includes insight and error correction, enabling one to navigate dangerous or technically difficult situations. Important in social functioning, executive cognition allows for the suppression of strong habitual responses or temptations.

The executive system organizes and prioritizes cognitive resources in such a way to allow for complex conceptualization of abstract problems and execution of detailed plans and actions. It is required for foresight or temporal planning, critical analysis of rules and limitations/abilities, focus for attainment of goals, and reflection for troubleshooting and adaptation. For previously encountered situations, a patient with dysexecutive syndrome could rely on learned, automatic physical and psychological responses. In novel situations, however, the patient does not have these automatic responses to fall back on, or the abilities to organize his thoughts in order to deal with the new circumstances. Patients are unable to reach a particular goal secondary to the fact that they cannot plan and execute the smaller individual steps to achieve the desired end. The end result in the patient is seen as apathetic and easily distractible. This can also be frustrating for a patient, which may lead to outbursts of anger.

Damage to the frontal lobes may occur through traumatic injury, mass lesions, cerebrovascular, degenerative disease, or infection. For example, the frontal lobes are affected by normal ageing and pathologic, degenerative processes such as multiple sclerosis, Huntington disease, and Alzheimer disease. Cerebrovascular disease, such as the occlusion or hemorrhage of the anterior communicating artery, also leads to damage of the frontal lobes. The dominant neurotransmitter in the frontal lobe is dopamine. Low levels of dopamine often present as problems in frontal lobe functioning, one example of such being schizophrenia.

The most commonly cited example of a dysexecutive patient is that of Phineas Gage. Mr Gage sustained injury to his prefrontal cortex (PFC) following a railroad accident in 1848, where a 4 ft, 13 lb tamping iron went in under his left cheek bone and out through the top of his head. Mr Gage went from being an efficient foreman, to an impulsive, profane individual, with an inability to plan and carry out productive goals. While intelligence is intact, patients with frontal lobe damage show difficulty with emotional control, social interaction, and memory. This disinhibition is attributed to a disconnection between the PFC and the autonomic nervous system. Without a “warning” to alert the individual to a dangerous, undesirable, or sensitive situation, executive decision making is severely hampered. As such, executive cognition may not act so much to inform us of what behaviors are appropriate, but more to deter us from inappropriate interactions. The difficulty interpreting environmental stimuli contributes to the previously described social dysfunction and impaired learning (feedback to guide behavior).

The impulse-control difficulties leading to social dysfunction also may manifest as utilization behavior. For example, without instruction or reason, patients may be compelled to use daily objects within their visual field. For example, if a patient were to see a toothbrush in front of him, he would begin to brush his teeth, and do so repeatedly, even if he had already brushed his teeth. When asked why they are using this object without purpose, patients tend to confabulate. Patients may also perseverate in speech and action.

Spontaneity appears to originate in the frontal lobes as well. Patients with frontal lobe damage have limited facial expression, and can have either increased spontaneity of speech (right frontal) or decreased (left frontal).

Patients may also have deficits of declarative memory or memory for temporal order of events. Working memory or attention is frequently impaired. This is in contrast to the declarative memory deficits found with hippocampal damage.

COMPREHENSION QUESTIONS

Refer to the following case scenario to answer questions 47.1-47.2:

A 29-year-old man is hospitalized following a motorcycle accident in which he was thrown from his bike unhelmeted, and suffered a head injury. Following several weeks of sedation and intubation in the ICU, he physically recovers enough to be sent home with his family. They report, however, that his personality has changed from before the accident, and they want to know if his head injury could be responsible.

[47.1] The patient’s family report that prior to the accident he was very organized and knew what he wanted out of life. Now he just sits around, not really caring about anything, lets people walk all over him, and is completely incapable of planning anything. Damage to what region of this man’s brain could account for these symptoms?

A. Dorsolateral frontal cortex

B. Orbitofrontal cortex

C. Parieto-occipital cortex

D. Temporo-occipital cortex

[47.2] The patient’s family report that prior to the accident he was a wellbehaved, somewhat reserved person, who was very reliable and dependable. Since the accident he has behaved very inappropriately, shirking responsibility, and bouncing from one activity to another. They say he doesn’t seem to have any kind of internal filter anymore, and doesn’t seem to care about social norms, doing whatever he wants, whenever he wants. Damage to what region of the brain could account for these symptoms?

A. Dorsolateral frontal cortex

B. Orbitofrontal cortex

C. Parieto-occipital cortex

D. Temporo-occipital cortex

[47.3] The physician sees a patient in an inpatient psychiatric hospital who was “treated” for schizophrenia with a frontal lobotomy a number of years ago. He is very calm and shows very little emotion, and is relatively disinterested in what is going on around him. In addition to these findings, in which process is he most likely to have deficits?

A. Visuospatial processing

B. Language production

C. Motor learning

D. Solving novel problems

Answers

[47.1] A. The dorsolateral frontal cortex is associated with planning and strategy formation and lesions here usually cause apathy, poor planning ability, and excessively passive behavior, as seen in this patient. The frontal lobes in general are involved in executive function, which consists of, among other things, planning, problem solving, abstract thinking, judgment, and behavioral inhibition.

[47.2] B. This man has a lesion in the orbitofrontal cortex, which is associated with behavioral inhibition. Patients with lesions in this area typically behave poorly in social situation, and often engage in hypersexual behavior, abuse alcohol and drugs, and may engage in compulsive gambling.

[47.3] D. This patient, who has had a frontal lobotomy, would be expected to have deficits in executive function such as solving novel problems. Patients with frontal lobe dysfunction can often work their way through problems that they have experienced before because they can rely on the learned behavior from prior encounters. When confronted with a novel situation, however, they have great difficulty in problem solving and planning what to do.

NEUROSCIENCE PEARLS ❖ The executive function of the frontal lobes coordinates adaptive and problem-solving abilities when presented with a new situation. ❖ The frontal lobes allow for warnings of social norms, allowing for the suppression of strong habitual responses or temptations. ❖ Traumatic brain injury involving the frontal lobe leads to problems with emotional control, social interaction, and memory, despite the fact that intelligence is normal.

REFERENCES

Adolphs R, Tranel D, Damasio AR. The human amygdala in social judgment. Nature. 1998 Jun 4;393(6684):470-474. 

Saver JL, Damasio AR. Preserved access and processing of social knowledge in a patient with acquired sociopathy caused by ventromedial frontal damage. Neuropsychologia. 1991;29(12):1241-1249.

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