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Dr. Joy Hirsch, head of Memorial Sloan-Kettering Hospital's functional M.R.I. Laboratory, and her graduate student, Karl Kim, found that second languages are stored differently in the human brain, depending on when they are learned. Babies who learn two languages simultaneously, and apparently effortlessly, have a single brain region for generating complex speech, researchers say. But people who learn a second language in adolescence or adulthood possess two such brain regions, one for each language. To explore where languages lie in the brain, Dr. Hirsch recruited 12 healthy bilingual people from New York City. Ten different languages were represented in the group. Half had learned two languages in infancy. The other half began learning a second language around age 11 and had acquired fluency by 19 after living in the country where the language was spoken. With their heads inside the M.R.I. machine, subjects thought silently about what they had done the day before using complex sentences, first in one language, then in the other. The machine detected increases in blood flow, indicating where in the brain this thinking took place. Activity was noted in Wernicke's area, a region devoted to understanding the meaning of words and the subject matter of spoken language, or semantics, as well as Broca's area, a region dedicated to the execution of speech, as well as some deep grammatical aspects of language. None of the 12 bilinguals had two separate Wernicke's areas, Dr. Hirsch said. But there were dramatic differences in Broca's areas, Dr. Hirsch said. In people who had learned both languages in infancy, there was only one uniform Broca's region for both languages, a dot of tissue containing about 30,000 neurons. Among those who had learned a second language in adolescence, however, Broca's area seemed to be divided into two distinct areas. Only one area was activated for each language. These two areas lay close to each other but were always separate, Dr. Hirsch s

Other, non-human primates have Broca's and Wernicke's areas in their brains, as do humans. In both species, the Broca's region represents non-linguistic hand and mouth movements. Evidence also suggests that both species may have mirror neurons in this region that are involved in understanding the actions and intentions of others. In both macaques and humans, this region is likely involved in producing orofacial expressions and in understanding the intentions behind orofacial expressions of others. In humans, it has evolved an additional communicative function, namely speech production. Interestingly however, it does not appear to be involved in monkey vocalizations, which are instead mediated by limbic and brainstem areas. In both species, the region represents non-linguistic hand and mouth movements. Evidence also suggests that both species may have mirror neurons in this region that are involved in understanding the actions and intentions of others. In both macaques and humans, this region is likely involved in producing orofacial expressions and in understanding the intentions behind orofacial expressions of others. In humans, it has evolved an additional communicative function, namely speech production. However, unlike in humans, Broca's area does not appear to be involved in monkey vocalizations, which are instead mediated by limbic and brainstem areas. Regarding Wernicke's area, which is responsible for language comprehension in humans, evidence suggests that the left superior temporal gyrus is specialized for processing species-specific calls in macaques, just as it is specialized for speech comprehension in humans.

Neuroimaging studies suggest that sign languages are complex linguistic systems processed much like spoken languages, even though they're gestural/visual, not oral. Wernicke's area activates when perceiving sign language; Broca's when producing sign language. In deaf people, lesions in left hemisphere "speech centres" like Broca's and Wernicke's areas produced significantly more sign errors on naming, repetition and sentence-comprehension tasks than signers with damaged right hemispheres.

This site is very insightful as to the differences in language development in the brain between those that learn a second language in childhood and those that learn the language as adults. It explains briefly the idea of a critical period and discusses the interesting aspects that come along with learning a second language later in life. It mentions Broca's and Wernicke's area.

3D interactive brain with labels: can select from left menu particular areas to look at, such as Broca's and Wernicke's

Excellent study. "While it has long been recognized that certain areas in the brain's left hemisphere enable us to understand and produce language, scientists are still figuring out exactly how those areas divvy up the highly complex processes necessary to comprehend and produce language. ... Two brain areas called Broca's region and Wernicke's region serve as the main computing hubs underlying language processing, with dense bundles of nerve fibers linking the two ... Working with patients suffering from language impairments because of a variety of neurodegenerative diseases, Wilsons' team used brain imaging and language tests to disentangle the roles played by the two pathways. ... The study marks the first time it has been shown that upper and lower tracts play distinct functional roles in language processing."

While the left hemisphere of the brain is where the processing and understanding of language is, different sections of the brain control different parts of language. Two separate areas of the brain control the ability to remember and understand specific words, and the other controls how we construct sentences and make sense of them. If one of these sections is damaged, the other can still work properly, so it is possible to be able to remember words and what they mean but not know how to create sentences.

Stephen Wilson, an associate professor in the University of Arizona's Department of Speech, Language, and Hearing Sciences, studied the upper and lower white-matter connecting pathways between Broca's region and Wernicke's region: the two areas of the brain that are hubs for language processing. Brain imaging and language tests were used to examine patients suffering from language impairments caused by neurodegeneration. Wilson discovered the pathways have distinct functions. Damage to the lower pathway affects lexicon and semantics: "You forget the name of things, you forget the meaning of words. But surprisingly, you're extremely good at constructing sentences." Conversely, damage to the upper pathway creates problems in syntactic processing and figuring out the relationship between words in a sentence.

Language isn't found in just one part of the brain but rather in separate individual parts that are responsible for different aspects of language. Neurodegentive diseases that target specific areas of the brain affecting language, only have a partial effect on the patients ability to understand and communicate.

The recent advent of brain-mapping technology-which allows doctors to create a precise digital replica of a person's brain cartography--has made more surgeons comfortable with the concept of keeping patients awake while they operate. This article profiles a woman, Brittany Capone, who's having open-brain surgery to remove a tumor that's dangerously close to a region in the brain that controls speech and the ability to comprehend language. By doing the operation while she is awake and speaking, her surgeon, Dr. Philip Gutin, can figure out exactly where the offending growth ends and the area of the brain called the Wernicke's center begins. This way, Gutin can see how close he can cut without permanently affecting his patient's ability to talk. What neurosurgeons are learning through mapping and documenting their experiences is also informing general knowledge about where brain structures are located and the slightly different positions they can take in different people.