私醫聯招 英文歷屆試題｜第 348 題

For centuries, researchers have been investigating how the human brain produces and comprehends human languages. According to ancient Greeks, injuries to the head could affect language use, which refers to the term aphasia, meaning language problems associated with a head injury. The best way to examine language in the brain was by checking injuries to the head or brain and pinpointing their location and then examining the type of language impairment, through a postmortem examination of a patient's brain. Much of the brain damage in senior people was the result of strokes, whereas in younger people the damage was often caused by a trauma. Among victims, as many people know, a stroke in the right side of the brain affects the left side of the body and vice versa. Through studying brain injuries, human language is much more present in the left hemisphere than in the right. Interestingly, bilingual patients with head injuries show that sometimes one language is affected while the other is not, which illustrates how brain stores language.

Paul Broca, a French surgeon, discovered that speech production was hampered by injuries to the left frontal cortex. Patients with injuries to the left frontal cortex can frequently comprehend language well but are unable to produce much speech. This area of the brain has been called Broca's area. People suffering from speech loss due to injury there have Broca's aphasia.

The opposite type of injury also occurs, in which a patient can produce words that sound normal but is difficult to comprehend speech. Usually the words are mixed together, which really makes no sense. This region of brain becomes known as Wernicke's area, named after Karl Wernicke, a German doctor who found the correlation between comprehension difficulties and this area of the brain in the 1870s.

Obviously, language production and comprehension are correlated with each other. There is a bundle of nerves called the arcuate fasciculus that connects Broca's area to Wernicke's area. When the arcuate fasciculus is injured, the resulting aphasia is called conductive aphasia. Patients with the injury usually have good comprehension of language and can speak well. But their speech is mixed with unnatural stops and pauses.