Chapter Fortysix

46.15 Language Areas of the Cortex Different regions of the left cerebral cortex participate in the processes of (a) repeating a word that is heard and (6) speaking a written word.

Broca's area results in halting, slow, Speech poorly articulated speech or even Hearing complete loss of speech, but the patient can still read and understand language. In the temporal lobe, close to its border with the occipital lobe, is Wernicke's area, which is more involved with sensory than with motor aspects of language. Damage to Wernicke's area can cause a person to lose the ability to speak sensibly while retaining the abilities to form the sounds of normal speech and to imitate its cadence. Moreover, such a patient cannot understand spoken or written language. Near Wernicke's area is the angular gyrus, which is believed to be essential for integrating spoken and written language.

Normal language ability depends on the flow of information among various areas of the left cerebral cortex. Input from spoken language travels from the auditory cortex to Wernicke's area (Figure 46.15a). Input from written language travels from the visual cortex to the angular gyrus to Wer-nicke's area (Figure 46.15b). Commands to speak are formulated in Wernicke's area and travel to Broca's area and from there to the primary motor cortex. Damage to any one of those areas or the pathways between them can result in aphasia. Using modern methods of functional brain imaging, it is possible to see the metabolic activity in different brain areas when the brain is using language (Figure 46.16).

What is consciousness?

This chapter has only scratched the surface of our knowledge about the organization and functions of the human brain, but it may give you some idea of the incredible challenge that neurobiologists face in trying to understand their own brains. Progress is being aided by powerful new technologies such as patch clamping (see Figure 44.11), functional imaging, and neurochemical and molecular methods. However, even these sophisticated new research tools may not allow us to answer the question "What is consciousness?"

If you see a black dog running across a field, you are conscious of the fact that it is a dog, it is black, and it is a Labrador retriever. You may remember that the dog's name is Sarina, that he belongs to your friend Meera, and that he is 6 years old. From what you have learned in this chapter, imagine how many neurons would be active during this experience: neurons in the visual system, the language areas, and in different

(b) Speaking a written word

Angular gyrus

(a) Repeating a heard word

Motor

Broca's

Angular gyrus

Wernicke Brocas And Primary Areas

Vision

Wernicke's area

Vision

(b) Speaking a written word

regions of association cortex. But is being conscious of the black dog simply a result of the fact that all of these neurons are firing at the same time? Your brain is simultaneously processing many other sensory inputs, but you are not necessarily conscious of those inputs. What makes you conscious of the black dog and associated memories and not of other information the brain is processing at the same time?

If we could describe all the neurons and all the synapses involved in the conscious experience of seeing and naming a black dog, and then build a computer with devices that modeled all these neurons and connections, would that computer be conscious? It has been said that the question of consciousness resolves into two types of problems: "easy" and "hard." The easy problems deal with all the cells and circuits that process the information that is involved in conscious ex-

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Brain Blaster

Brain Blaster

Have you ever been envious of people who seem to have no end of clever ideas, who are able to think quickly in any situation, or who seem to have flawless memories? Could it be that they're just born smarter or quicker than the rest of us? Or are there some secrets that they might know that we don't?

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