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From thought to language
Sub-Topics
Communicating in Words

Linked
Help Link : Building Gab: Part One Link : Scientists Identify a Language Gene Link : Researchers Confirm: Language and Speech Are All in the Mind
Link : INNATENESS, AUTONOMY, UNIVERSALITY? Link : The FOXP2 story Link : FOXP2 in focus: what can genes tell us about speech and language? Link : From Genes to Words
Link : FOXP2 Link : Gene change speaks to language malady
Researcher
Research : Learning about language : Professors Andrew Copp, David Gadian and Faraneh Vargha-Khadem
Experiment
Experience : FOXP2 and the mirror system
Original modules
Tool : Brain Imaging Brain Imaging

Among the various markers used to study genetic diversity in individuals and populations, the most interesting are those DNA sequences that are inherited from only one parent: mitochondrial DNA (mtDNA), which is inherited from the mother, and the Y chromosome, which is inherited from the father. These genetic markers are very useful, because their DNA sequences are not subject to meiotic recombination. This makes it easier to identify a population’s paternal and maternal ancestors.

In contrast, each of us inherits two copies of the FOXP2 gene: one from our mother, and one from our father, located on each of the two chromosomes in pair 7. Both copies, it appears, must be intact for our language functions to be normal.

Link : Genetic Origins


GENES THAT ARE ESSENTIAL FOR SPEECH

The identification of the FOXP2 gene on human chromosome 7 established the first scientific connection between heredity and language. Subsequent research provided more information about the protein produced by this gene. This protein is what is known as a transcription factor, meaning that it can bind directly to DNA molecules to regulate the expression of other genes—including genes possibly involved in the development of the brain areas associated with language. In other words, if you think of all the genes that contribute to language as forming a tree, then you can think of the FOXP2 gene as the trunk of that tree.


Average activation recorded by fMRI during a word-generation task in normal subjects and in subjects with specific language impairments

 

It is no surprise, then, that when one of a person’s two copies of this gene is defective, that person will suffer from specific language impairments (SLI). Moreover, brain-imaging studies have shown that the brains of people who had SLI did in fact display many abnormalities in areas of key importance for language. In particular, in these subjects, both caudate nuclei and Broca’s area were smaller, and the left caudate nucleus was hyperactive during tasks involving oral expression.

This atrophy of the caudate nucleus, a structure involved in motor control, might have something to do with the great difficulties that people with the mutant version of the FOXP2 gene have in moving their lips and tongue. Some researchers therefore believe that it is the human version of the FOXP2 gene that enables the fine mouth and facial movements that make articulate language possible.

Some researchers have even asserted that in the final analysis, FOXP2 may not be a “language gene”, but rather a gene in which defects can cause motor disorders serious enough to prevent the use of language. Other explanations that avoided directly linking FOXP2 with language included the suggestion that defects in this gene might diminish intellectual faculties to such an extent that language became impossible. But subsequent experiments have shown that the links between FOXP2 and language do in fact appear to be very close.

Thus, though SLI may tend to strike those family members who score lowest on IQ tests, some people with this condition achieve normal IQ scores, while others may even achieve higher scores than their family members who do not have it.

People with SLI also have trouble in identifying some elementary sounds of language, as well as in understanding sentences, using grammar, and so on. The observed atrophy in Broca’s area may also affect their language abilities, because this area contains mirror neurons that some authors consider very important for language development, and because the destruction of this area is known to cause many different kinds of aphasias.

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