The specific learning disabilities (LD) category, dating back to its origin in the early 1960s, was built on the assumption that central nervous system dysfunction was the underlying cause of why these individuals struggled to achieve at levels commensurate with their peers. More than three decades of testing and classifying, teaching and implementing programs of related services and support has left us with a definition of LD that includes:
at least average intellectual capacity
a significant (and unexplained) discrepancy between achievement and expected potential
the exclusion of mental retardation, emotional disturbance, sensory impairment, cultural differences or lack of opportunity to learn
central nervous system dysfunction as the basis of the presenting problem(s)
While our systems for identifying learning disabilities and for providing instruction and support to these individuals in school and in the workplace have undergone considerable change (for the better) during these years, our understanding of the neurobiology of learning disabilities has lagged behind. This is due, in great part, to the complex nature of the brain, the unique ways that each person processes information, and the ever-changing interrelationship between the brain and a person's experiences in the world.
What We Know and What We Presume
We know that:
learning disabilities are a heterogeneous group of disorders that have a negative impact on learning. And LD in reading is the area about which we currently know the most. Dating back to the 1800s, it was shown that variations in brain development (discovered by autopsy) were connected in some way to difficulties in learning to read. Today, using sophisticated brain imaging tools in healthy subjects, we can now say with assurance that a number of regions and structures in the brain are associated with particular skills that support the development of reading. (Drs. Sally & Bennett Shaywitz of Yale University refer to a "neural" signature for phonological processing' characterizing weaknesses evident in dyslexia.)
learning disabilities are persistent throughout the lifespan and that there is a strong genetic component in the development of these disorders, with rates of reading disabilities in families estimated to be as high as 35-45%. (The Institute for Behavioral Genetics at the University of Colorado is a fine resource for more information about this topic.)
some learning disabilities are congenital in nature, meaning that they can be traced to biological influences during prenatal gestation; fetal alcohol effects, fetal cocaine exposure, and perhaps even maternal cigarette smoking are examples of these types of contributing factors to LD.
learning disabilities are both familial and heritable, meaning that they can be caused by both environmental influences and family genetics. This is an important finding because it provides opportunities for early identification of children who are 'at-risk' and even help with the formal identification of LD in adults.
Learning disabilities (LDs) are real. They affect the brain's ability to receive, process, store, respond to, and communicate information. LDs are actually a group of disorders, not a single disorder. Learning disabilities are not the same as intellectual disabilities (formerly known ... More >
NCLD, with the State of Learning Disabilities, has published a critical report that will further the debate over how to strengthen the programs and policies we have in place to serve and protect students and adults with learning disabilities.
- Thomas H. Kean, NCLD Board Member and f... More >
What Are Learning Disabilities?
Learning disabilities (LD) are a group of varying disorders that have a negative impact on learning. They may affect one’s ability to speak, listen, think, read, write, spell or compute. The most prevalent LD is in the area of reading, known as d... More >
Truth be told, learning disabilities (LD) are not easily explained. While they are “specific” to any number of areas of learning (such as reading, math, and writing) they are also often overlapping or co-occurring, meaning that individuals with LD can have significant challenges ... More >
Even though some three million school-age children are classified as having specific learning disabilities (LD), this category of special need is often widely misunderstood. Surveys of both parents and educators confirm that many people mistakenly link LD with mental retardation and ... More >
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The specific learning disabilities (LD) category, dating back to its origin in the early 1960s, was built on the assumption that central nervous system dysfunction was the underlying cause of why these individuals struggled to achieve at levels commensurate with their peers. More than three decades of testing and classifying, teaching and implementing programs of related services and support has left us with a definition of LD that includes:
