A team of researchers led by UC Davis MIND Institute Director Leonard Abbeduto will investigate the effectiveness of testing procedures to examine the spoken language development of people with fragile X syndrome and people with Down syndrome, through a new five-year, $3 million grant from the Eunice Kennedy Shriver National Institute of Child Health and Human Development of the National Institutes of Health.
The grant will be used to determine whether these procedures can be utilized to gauge the efficacy of new drugs under development for treating the cognitive and behavioral challenges that face individuals with intellectual disabilities, including fragile X syndrome and Down syndrome.
“Language improvement is an important target for many of these promising new drugs," Abbeduto said. "However, we don’t yet have tools sensitive and accurate enough to measure change in language in clinical trials. This study may lead us to understand the efficacy of these drugs.”
Fragile X syndrome is the most common inherited cause of intellectual disability and ranges in severity from learning disabilities to more severe cognitive impairment. It is the most common single-gene cause of intellectual disability and of autism spectrum disorder. Down syndrome, also known as trisomy 21, is a chromosomal condition caused by the presence of all or part of a third copy of chromosome 21. It is the leading genetic cause of intellectual disability. Down syndrome is accompanied by distinctive facial characteristics and also can be accompanied by other medical conditions, including congenital heart defects.
The research conducted in Abbeduto’s lab has focused, in part, on identifying the specific profiles of language development that characterize fragile X syndrome and Down syndrome, including the aspects of language that are similar or differ between these two disorders.
For the current study, Abbeduto will collaborate with researchers at Rush University Medical Center in Chicago, Emory University School of Medicine in Atlanta, the University of Wisconsin, Madison and the University of Arizona, Tucson. The study will evaluate the reliability and sensitivity of a language-evaluation procedure that Abbeduto has pioneered for two decades called expressive-language sampling.
Expressive-language sampling involves collecting actual samples of spoken language from individuals in different highly scripted and structural contexts and at different times and comparing them with one another to evaluate growth and change in language usage. In the funded project, results of expressive-language sampling will be compared to results obtained from standardized tests of language development to examine the relationship between the skills measured with each respective measure.
Advances in molecular genetics have identified more than 1,000 genetic causes of intellectual disability. This research has led to disease-specific treatments with several pharmaceuticals under development to address the symptoms of different syndromes that result in intellectual disability. However, the advances are hampered by a lack of validated outcome measures against which response-to-treatment can be evaluated for individuals with these developmental disabilities. Expressive-language sampling techniques, while widely used for clinical and behavioral research purposes, have not yet been validated for use as outcome measures for studies of drug treatment efficacy. The newly funded study will address this issue by examining the short-term consistency and long-term sensitivity and the validity of expressive-language sampling procedures.
To conduct the study, the researchers will enroll a total of 300 participants, 150 with fragile X syndrome and 150 with Down syndrome. Each site will recruit and test a total of 60 participants over the course of the five-year project. Three age groups will be recruited for testing: 6 to 11; 12 to 17; and 18 to 23 years.
Each of the study participants will be tested using both standardized tests and with the expressive-language sampling procedures. The language-sampling procedure consists of obtaining samples of spoken language in two different contexts. One is narrating a story depicted in a wordless picture book; the second is performance during a scripted 10-minute conversation with an examiner. The participants will be tested at three different times: an initial testing session, one held two weeks later and a follow-up test after two years.
The study’s hypothesis is that, for individuals with intellectual disabilities, standardized tests do not offer the nuanced information necessary to gauge whether language is improving over time, because standardized tests are de-contextualized rather than naturalistic and because they have a “floor effect:” Individuals with intellectual disabilities often receive very low scores on standardized tests, limiting the utility of such tests to provide specific information on how the individual uses language in every day life.
Expressive-language sampling, on the other hand, can provide detailed information on the vocabulary an individual uses and the complexity of the sentences they are able to produce and even the intelligibility of their speech. This kind of information is necessary to judge the effectiveness of drug-treatment protocols as well as to guide planning for behavioral interventions.
“The preliminary data suggests that our procedures can measure even subtle but important changes in language, and pharmaceutical companies see the potential utility of these procedures,” Abbeduto said.