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Representation of language acquisition in the brain

Recent advances in the field of neuroimaging technology have allowed for a better understanding of how language acquisition is manifested physically in the brain. Language acquisition generally occurs in children during a period of rapid increase in brain development. At this point in development, a child has several more neural connections than he or she will have as an adult. This allows the child to be more capable of learning new things and allows the child to be more effective in learning new materials than it would be as an adult.

The Sensitive Period

Language acquisition has been studied from the perspective of developmental psychology and neuroscience, which looks at learning to use and understand language parallel to a child's brain development. It has been ascertained through empirical research on developmentally normal children as well as extreme cases of language deprivation that there is a "sensitive period" of language acquisition in which infants have the ability to learn any language. This plasticity diminishes as a child becomes gradually more exposed to the specific sounds and structure of his or her language environment. This allows the child to promptly become a native speaker of that language. As Christophe Pallier noted, "Before the child begins to speak and to perceive, the uncommitted cortex is a blank slate on which nothing has been written. In the ensuing years much is written, and the writing is normally never erased. After the age of ten or twelve, the general functional connections have been established and fixed for the speech cortex." According to the sensitive or critical period models, the age at which a child acquires the ability to use language is a predictor of how well he or she is ultimately able to use language.[32] However, there may be a cutoff age at which becoming a fluent and native-like user of a language is no longer possible. Our brains may be automatically wired to learn languages, but this ability does not last into adulthood in the same way that it exists during development in childhood. By the onset of puberty (around age 12), language acquisition has typically been solidified and it becomes more difficult to learn a language in the same way a native speaker would. At this point, it is usually a second language that a person is trying to acquire and not a first.[33]

This sensitive period is typically never missed by cognitively normal children- humans are extremely well prepared to learn language, and unless there is a complete lack of language in the environment it is almost impossible not to learn language. Researchers are unable to experimentally test the effects of the sensitive period of development on language acquisition because it would be unethical to deprive children of language until this period is over. However, case studies on abused, language deprived children show that they were extremely limited in their language skills even after instruction; such examples can be seen in Genie, Isabelle and Victor.[34]

Neurocognitive research

According to several linguists, neurocognitive research has confirmed many standards of language learning. Standards such as: "learning engages the entire person (cognitive, affective, and psychomotor dominas), the human brain seeks patterns in its searching for meaning, emotions affect all aspects of learning, retention and recall, past experience always affects new learning, the brain's working memory has a limited capacity, lecture usually results in the lowest degree of retention, rehearsal is essential for retention, practice [alone] does not make perfect, and each brain is unique" (Sousa, 2006, p. 274). In terms of genetics, the gene ROBO1 has been associated with phonological buffer integrity or length [50]

Although it is difficult to determine without invasive measures which exact parts of the brain become most active and necessary for language acquisition, fMRI and PET technology has allowed for some conclusions to be made about where language may be centered. The two main areas where language has been connected in the brain are Wernicke's area and Broca’s area. Wernicke’s area is part of the cerebral cortex linked to speech and is involved in the understanding of written and spoken language. Broca's area is a region of the hominid brain with functions linked to speech production. Kuniyoshi Sakai proposed, based on several neuroimaging studies, that there may be a "grammar center" where language is primarily processed in the left lateral premotor cortex (located near the pre central sulcus and the inferior frontal sulcus). Additionally, these studies proposed that first language and second language acquisition may be represented differently in the cortex.[34]