The Brain and Language

• 36-4 What brain areas are involved in language processing and speech?

We think of speaking and reading, or writing and reading, or singing and speaking as merely different examples of the same general ability—language. But consider this curious finding: Damage to any of several cortical areas can produce aphasia, impairment of language. Even more curious, some people with aphasia can speak fluently but cannot read (despite good vision). Others can comprehend what they read but cannot speak. Still others can write but not read, read but not write, read numbers but not letters, or sing but not speak. These cases suggest that language is complex, and that different brain areas must serve different language functions.

aphasia

impairment of language, usually caused by left hemisphere damage either to Broca’s area (impairing speaking) or to Wernicke’s area (impairing understanding).

Indeed, in 1865, French physician Paul Broca confirmed a fellow physician’s observation that after damage to an area of the left frontal lobe (later called Broca’s area) a person would struggle to speak words, yet could sing familiar songs and comprehend speech. A decade later, German investigator Carl Wernicke discovered that after damage to a specific area of the left temporal lobe (Wernicke’s area), people were unable to understand others’ words and could speak only meaningless sentences. Asked to describe a picture that showed two boys stealing cookies behind a woman’s back, one patient responded: “Mother is away her working her work to get her better, but when she’s looking the two boys looking the other part. She’s working another time” (Geschwind, 1979).

Broca’s area

helps control language expression—an area of the frontal lobe, usually in the left hemisphere, that directs the muscle movements involved in speech.

Wernicke’s area

a brain area involved in language comprehension and expression; usually in the left temporal lobe.

Today’s neuroscience has confirmed brain activity in Broca’s and Wernicke’s areas during language processing (Figure 36.2). But we also now know that the brain’s processing of language is complex. Broca’s area coordinates the brain’s processing of language in other areas as well (Flinker et al., 2015; Tremblay & Dick, 2016). Although you experience language as a single, unified stream, functional MRI scans would show that your brain is busily multitasking and networking. Different neural networks are activated by nouns and verbs (or objects and actions); by different vowels; by stories of visual versus motor experiences; by who spoke and what was said; and by many other stimuli (Perrachione et al., 2011; Shapiro et al., 2006; Speer et al., 2009). Moreover, if you’re lucky enough to be natively fluent in two languages, your brain processes them in similar areas, but in different areas if you learned a second language after the first (Berken et al., 2015). Bilingual spoken and signed language are also handled by different brain areas (Kovelman et al., 2014).

Figure 36.2 Brain activity when speaking and hearing words

The first illustration shows image of the broca’s area and motor cortex, active when speaking words. It shows a brain superimposed over a human head. A narrow vertically-oriented section, running from the center of the brain to the upper middle, is highlighted in blue. A oval-shaped section in the middle right of the blue section is highlighted in red.

The second illustration shows image of the auditory cortex and wernicke’s area. It shows a brain superimposed over a human head. A narrow vertically-oriented section, running from the center of the brain to the upper middle, is highlighted in blue. A oval-shaped section in the middle right of the blue section is highlighted in red.

AP^® EXAM TIP

You’ll notice that even though the brain was one of the major topics in Unit III, it keeps coming up. It’s a good idea to go back and review what you learned previously about the brain. Rehearse frequently, and you will not have much to relearn before the AP^® exam.

The point to remember: In processing language, as in other forms of information processing, the brain operates by dividing its mental functions—speaking, perceiving, thinking, remembering—into subfunctions. Your conscious experience of reading this page seems indivisible. But thanks to your parallel processing, many different neural networks are pooling their work to give the string of words coherence and meaning (Fedorenko et al., 2016). E pluribus unum: Out of many, one. We saw this also in Module 18’s discussion of vision, for which the brain engages specialized subtasks, such as discerning depth, movement, form, and color. And in vision as in language, a localized trauma that destroys one of these neural work teams may cause people to lose just one aspect of processing. In visual processing, a stroke may destroy the ability to perceive movement but not color. In language processing, a stroke may impair the ability to speak distinctly without harming the ability to read.

“ It is the way systems interact and have a dynamic interdependence that is—unless one has lost all sense of wonder—quite awe-inspiring.”

Simon Conway Morris, “ The Boyle Lecture,” 2005

* * *

Returning to our debate about how deserving we humans are the label Homo sapiens, let’s pause to issue an interim report card. On decision making and risk assessment, our smart but error-prone species might rate a B–. On problem solving, where humans are inventive yet vulnerable to confirmation bias and fixation, we would probably receive a better grade, perhaps a B+. On cognitive efficiency, our quick (though sometimes faulty) heuristics would earn us an A. And when it comes to our creativity, and our learning and using language, the awestruck experts would surely award the human species an A+.

Check Your Understanding

Ask Yourself

• There has been controversy at some universities about allowing fluency in sign language to fulfill a second-language requirement for an undergraduate degree. As you start planning for your own college years, what is your opinion?

Test Yourself

• If children are not yet speaking, is there any reason to think they would benefit from parents and other caregivers reading to them?
• ______________ ______________ is one part of the brain that, if damaged, might impair your ability to speak words. Damage to ______________ ______________ might impair your ability to understand language.

Answers to the Test Yourself questions can be found in Appendix E at the end of the book.