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Ch. 12 The Central Nervous System
Marieb - Human Anatomy & Physiology 7th Edition
Marieb, Hoehn7th EditionHuman Anatomy & PhysiologyISBN: 9780805359091Not the one you use?Change textbook
Chapter 12, Problem 22

Robert, a brilliant computer analyst, suffered a blow to his anterior skull from a falling rock while mountain climbing. Shortly thereafter, it was obvious to his coworkers that his behavior had undergone a dramatic change. Although previously a smart dresser, he was now unkempt. One morning, he was observed defecating into the wastebasket. Which region of Robert's brain was affected by the cranial blow?

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Step 1: Identify the key symptoms described in the problem: a dramatic change in behavior, loss of social norms (e.g., unkempt appearance), and inappropriate actions (e.g., defecating into a wastebasket). These symptoms suggest impairment in personality, decision-making, and social behavior.
Step 2: Recall the brain regions responsible for personality, social behavior, and executive functions. The prefrontal cortex, especially the frontal lobe, is known to regulate these higher cognitive functions and social conduct.
Step 3: Understand that the anterior skull blow likely affected the frontal lobe, as it is located at the front of the brain beneath the forehead and anterior skull.
Step 4: Connect the behavioral changes to damage in the prefrontal cortex, which is part of the frontal lobe. Damage here can lead to disinhibition, poor judgment, and changes in personality, consistent with Robert's symptoms.
Step 5: Conclude that the region of Robert's brain affected by the cranial blow is the frontal lobe, specifically the prefrontal cortex, which explains the observed behavioral changes.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Frontal Lobe Function

The frontal lobe is responsible for executive functions such as decision-making, social behavior, and personality. Damage to this area can result in changes in behavior, poor judgment, and loss of social inhibitions, which explains Robert's altered conduct after the injury.
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Prefrontal Cortex Role

The prefrontal cortex, part of the frontal lobe, regulates complex cognitive behavior and moderates social behavior. Injury here often leads to disinhibition, impulsivity, and inappropriate actions, such as Robert's unkempt appearance and socially unacceptable behavior.
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Localization of Brain Injury Symptoms

Identifying brain injury symptoms helps localize the affected region. Behavioral changes, loss of social norms, and poor self-care typically indicate damage to the anterior frontal regions, especially the prefrontal cortex, rather than other brain areas like the occipital or temporal lobes.
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