Learning Disabilities

With regard to causes, research extends to family, genetic, and neuroanatomic bases, with most work being done in language and reading disabilities. There appears to be heritability in language and reading LDs, with similar LDs being found in 35 percent to 45 percent of first-degree relatives. Also, identical twins are more likely to have similar LDs than fraternal twins. Chromosomes 6 and 15 have been implicated frequently as possible genetic causes of LDs. Neuroimaging techniques, such as functional magnetic resonance imaging, have documented differences among dyslexic and nonreading-disabled individuals. Studies have found that in individuals with dyslexia, certain areas of the brain are different than in individuals without dyslexia. Nonetheless, there are no neuroanatomic or neuroelectric diagnostic tests that identify LDs in the brain. Although LDs are found more frequently in children subject to brain insult (such as premature birth and asphyxia), many children display LDs without any identifiable cause.