measure a range of cognitive processing abilities in adolescents and adults. Although behavioral tests are used for assessment and diagnosis, learning disabilities have come to be viewed as brain-based conditions caused by hereditary (genetic) factors and complex pathways of gene-brain-behavior relationships and their interaction with environment and experience. Modern brain imaging techniques show that both children and adults with reading disabilities show marked differences in brain structure and functions relative to typically developing readers. An important next step will be to test causal relations between these structural and functional anomalies and reading using prospective longitudinal designs. In addition, research is needed to better understand the relative contributions of environment (inadequate learning opportunities) and genetic factors (and their interaction) to the different brain trajectories of those with reading disabilities. Gene-brain-behavior research is needed especially to enhance understanding of the unique challenges faced by older learners.
Neurocognitive research shows the plasticity (change) of brains in response to interventions for struggling readers extends into young adulthood, but studies are needed with older adults to determine if the same patterns of neuronal reorganization would occur later in life in response to instruction. This question is also important to ask for adults without learning difficulties but who were nevertheless deprived of early opportunities to learn. Although still incomplete, research on brain-based developmental trajectories from childhood to adulthood suggests patterns of brain activation and consequently improved literacy performance that might be achieved with effective instruction and remediation of struggling readers. This research also suggests ways of measuring neurobiological change that may be useful in evaluating the effectiveness of interventions for adult learners.
For both reading and writing, extra time, various technological supports, and the teaching of cognitive strategies are accommodations that enhance competencies, although many aspects of reading and writing remain to be addressed in research, such as syntax and reading comprehension. Likewise, most published research on brain differences between typically developing and reading disabled learners focuses on phonological processing, decoding, or word reading, and a better understanding of neurobiological processes involved in disorders of syntax, comprehension, spelling, and writing is needed.
The findings in this chapter must be generalized with caution beyond those adults who have met the legal criteria for learning disabilities to which secondary and postsecondary institutions in the United States must adhere in providing services for students with learning disabilities. More research of the kind described is needed to characterize and determine how best to intervene with a broader range of adults in literacy education.