Introduction
Learning disabilities have been defined in various ways over history. Initially terms such as minimal brain dysfunction, word blindness, and dyslexia were widely used. The term learning disabilities then became more popular particularly with the advent of passage of P.L. 94-142 in 1975 (Goldstein, 1997). A definition proposed by the National Joint Committee for Learning Disabilities in 1981 suggested that "these disorders are intrinsic to the individual and presume to be due to central nervous dysfunction." (Hammill, Leigh, McNutt, & Larsen, 1981, p. 340). This definition included difficulties with reading, mathematics, listening comprehension, written language, and expressive/receptive language. Although learning disabilities has been understood to be a heterogeneous term, most lay people and many teachers interpret learning disabilities to mean difficulties in reading. The empirical field also shows this emphasis on reading with the abundance of articles about reading disabilities compared to those written on mathematics, written language, or social learning difficulties.
Learning disabilities have been found to be comorbid with other diagnoses including attention deficit hyperactivity disorder (ADHD), anxiety, depression, and others (Martinez & Semrud-Clikeman, in press). ADHD has been found to co-occur in approximately 20%-50% of children with reading difficulties depending on the method of calculating a learning disability (Semrud-Clikeman et al., 1992). ADHD has also been found to co-occur with difficulties in mathematics (Semrud-Clikeman, 2003), written language (Hargrave, Corlett, & Semrud-Clikeman, 2002), and social emotional learning disabilities (Semrud-Clikeman, 2003). Comorbidity of learning problems with other diagnoses makes it imperative to evaluate these possibilities when developing a remediation program for the child (Pennington, 1990). Moreover, our understanding of the contribution of these related but separate diagnoses to learning is just beginning to be understood. There is far more research evaluating the brain functioning in children with reading disabilities than those with other learning problems or those who show a combination of difficulties. Although the focus of this paper will be on reading disabilities due to restrictions in length and time, the other areas of learning disabilities are equally important and hopefully can be highlighted at another time.
The general procedure of identifying learning disabilities has been through the use of a discrepancy between measured ability (IQ) and achievement (Joshi, 1999). As noted by other speakers at this meeting, this type of assessment very narrow and does not directly lead to recommendations for remediation. It also ignores the various neuropsychological functions underlying the ability to read, speak, comprehend, write, and do mathematics well. This practice also has been found to over-identify those children with high IQs and average achievement and under-identify those with lower IQs and below average achievement (Birch & Semrud-Clikeman, 2002; Semrud-Clikeman et al., 1992).
The acknowledgment of deficient brain functioning in children with learning disabilities has become more widely accepted particularly with the advent of research evaluating the functioning of the brain. The findings of differential brain activation following remediation are very appropriate for this symposium. A discussion of the most recent findings about the neural structures involved in reading may highlight the various aspects of the learning process that need to be evaluated.
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