Sustained attention to response task performance trajectories in Down syndrome.

BACKGROUND: Sustained attention (SA) has been reported to be a unitary construct in youth with Down syndrome (DS), but additional analyses of how auditory and visual SA change over task presentation time are warranted. METHOD: The current study was a secondary data analysis employing multilevel modeling. Specifically, we compared auditory and visual sustained attention to response task (SART) performance trajectories within a group of 42 youth with DS aged 10 to 22 years. RESULTS: We found that auditory omission errors increased at a faster rate than visual omission errors over increasing SART block presentations in youth with DS. CONCLUSIONS: Youth with DS experience more SA lapses over time in the auditory than visual modality. Results have implications for academic instruction and assessment.

A cross-sectional analysis of executive function in Down syndrome from 2 to 35 years.

BACKGROUND: Previous research has indicated a unique profile of executive function (EF) in children and adolescents with Down syndrome (DS). However, there is a paucity of research on EF in adults with DS. This study aimed to gain a broader understanding of strengths and weaknesses in EF in DS from 2 to 35 years. METHOD: Parents of 112 individuals with DS between 2 and 35 years participated in this study. Parents either completed the Behaviour Rating Inventory of Executive Function - for individuals 6+ years - or the Behaviour Rating Inventory of Executive Function Preschool Version - for children 2-5 years. RESULTS: Results suggest not only overall difficulties but also patterns of strength and weakness within EF for individuals with DS. For the 2 to 5-year-old group, emotional control and shift were relative strengths, planning/organisation and inhibit were intermediate skills, and working memory was a relative weakness. For the 6 to 18-year-old group, emotional control and organisation of materials were relative strengths, inhibit and initiate were intermediate skills, and working memory, monitor, planning/organisation, and shift were relative weaknesses. Most abilities were consistent from 2 to 18 years, except shift, which decreased in preadolescence before beginning to recover in adolescence. Across the full age range (2-35 years), composite scores indicated quadratic trends in inhibit, working memory, and planning/organisation, and a cubic trend in shift, with EF abilities generally declining in middle childhood before recovering in adulthood. CONCLUSIONS: This study extends previous research on EF in DS by providing an initial description of EF profiles across the lifespan. More longitudinal and behavioural research is needed to further characterise the development of EF in DS.

Improving memory span in children with Down syndrome.

BACKGROUND: Down syndrome (DS) is characterized by impaired memory span, particularly auditory verbal memory span. Memory span is linked developmentally to several language capabilities, and may be a basic capacity that enables language learning. If children with DS had better memory span, they might benefit more from language intervention. The present study evaluates a home-based parent-implemented intervention designed to improve auditory memory span in children with DS. METHOD: Sixteen children with DS, age 6-14, completed one or two 3-month periods of memory training using overt cumulative rehearsal and auditory-only procedures. Children were divided into two groups. Group 1 completed 3 months of memory training followed by 3 months of visual activities, followed by three more months of memory training. Group 2 had the opposite schedule. Before and after each 3-month period, children came into the laboratory for memory assessment. RESULTS: Children improved in training sessions and a small amount on digit span, the primary proximal outcome assessment measure. Digit span improvement was linked to the memory training, as indicated by control comparisons and correlations. Improvement was correlated with language comprehension and verbal working memory, but not with non-verbal ability, age or home/behavioural variables. No improvement was evident on distal outcome measures (sentence memory and verbal working memory); however, a phonological similarity effect emerged coincidence with memory training, suggesting increased use of phonological codes in memory. CONCLUSIONS: Results suggest that some children with DS can improve their auditory verbal memory span with home-based rehearsal training, at least in limited ways. Children with good language and verbal working memory skills may be the best candidates for this type of training, even though they may show only small improvements. Still, small improvements in a severely impaired function are noteworthy, and justify further investigation.

Memory training for children with Down syndrome.

One well-established fact concerning cognitive and language development in individuals with Down syndrome is that working memory is particularly poor, with auditory working memory worse than visual working memory. Working memory serves the functions of control, regulation, and active maintenance of information and is critical in daily complex cognitive activities. Thus, there is a strong need to find effective and practical interventions targeted at improving working memory in individuals with Down syndrome. The present paper reviews research on rehearsal training and concludes that it can be used successfully to increase working memory in individuals with Down syndrome. However, there are still questions about whether auditory working memory can be improved reliably, whether improvement can be maintained over the long term, and whether improvement exists beyond any effect of increased attention. We describe our in-progress study which addresses these concerns.

Abilities underlying decoding differences in children with intellectual disability.

Researchers in recent years have made much progress towards understanding why some children struggle to learn to read. However, little of this research has involved children with intellectual disability associated with an IQ < 70 (ID, also called mental retardation). In the present analysis, the authors examined cognitive similarities and differences between stronger and weaker decoders, all of whom have ID. The 65 children with ID in the present analysis were initially referred by their teachers for a study that involved training basic phonological reading skills. The present analysis compares 21 children who were excluded from the training study because their decoding skills were already too high with 44 children whose decoding skills were low enough for the training study. The groups were compared on general intelligence, language ability, phonemic awareness and phonological memory. Initial analyses showed that the stronger decoders were significantly better than weaker decoders in language ability, phonemic awareness and rehearsal in phonological memory, but not in intelligence. They were also significantly older than weaker decoders. When age was covaried out, the groups differed significantly only in rehearsal in phonological memory, although the difference for phonemic awareness was marginally significant when the poorest performers were excluded. When intelligence is substantially limited, the ability to rehearse or refresh phonological codes in working memory plays a major role in determining children's success in learning to read. This ability appears to be more important than intelligence, language ability and phonemic awareness. It is possible that the reason the phonemic awareness measure was not as good at distinguishing the groups as the phonological rehearsal measure was because the former did not involve assembling phonological output. It is suggested that it is the combination of poor phonological representation and poor phonological output assembly that makes decoding difficult for some children with ID.

Is the phonological loop responsible for intelligence-related differences in forward digit span?

Children with mild mental retardation were compared with CA-matched and verbal-age-matched children without mental retardation on a forward digit span task. Forward digit span is typically used as a measure of the phonological loop (Baddeley, 1986). We hypothesized that intelligence-related differences in forward digit span are largely due to central executive functioning rather than phonological loop functioning. Results showed that the highly significant group difference in forward digit span was reduced to nonsignificance when a measure of central executive functioning was covaried out.

Cognitive representation of motion in individuals with mental retardation.

Participants with and without mental retardation were compared on their tendency to show the representational momentum effect when viewing a stimulus array that implied motion. The representational momentum effect occurs when, due to implied or apparent motion, an object is more likely to be remembered slightly shifted in the direction of motion rather than against the direction of motion. Participants with mental retardation showed the representational momentum effect as did participants without mental retardation, though the magnitude of the memory shift was smaller for participants with mental retardation. Results suggest that individuals with mental retardation cognitively process motion information in the same general way as do those without mental retardation, although less efficiently.

Implicit and explicit memory in individuals with mental retardation.

Students with and without mental retardation from three age groups were compared on implicit and explicit memory tasks. Consistent with previous research on intelligence-related differences in controlled and automatic processes, students without mental retardation performed better than those with mental retardation on the explicit memory task, but there was no difference between groups on the implicit memory task. For both groups implicit and explicit memory increased from age 6 to 8 to age 10 to 12, but did not significantly increase to age 15 to 17. Because implicit memory appears to be a relative strength for students with mental retardation, we suggest further exploration into broader types of implicit processes that may be useful in training situations.

Assessment of basic cognitive abilities in relation to cognitive deficits.

A modal model of information-processing was used to select a battery of nine tasks of basic cognitive ability (learning, relearning, reaction time, probe recall, Sternberg search, self-paced probe, stimulus discrimination, tachistoscopic full report, tachistoscopic partial report). Parameters from these tasks operationalized the model. After extensive pilot testing of the tasks to establish reliability, we tested 40 subjects (20 with mental retardation and 20 college students) on all tasks and the WAIS-R. The parameters from the tasks were generally reliable (.7 through .9) and had low correlations with IQ (average about .37). Nearly all of the major cognitive parameters differentiated significantly between groups. A subset of the basic cognitive parameters predicted IQ with an estimated multiple correlation in the general population of .72. Prediction of IQ using basic cognitive parameters was better for subjects with mental retardation than for college students. A modified version of the modal model was supported. Results show that individual differences in higher mental processes are highly dependent on basic cognitive abilities and can be predicted from them. These findings have substantial implications for the development of models of information-processing.

Reading instruction for students with moderate mental retardation: review and analysis of research.

Three areas of research on reading instruction for children with moderate mental retardation were reviewed: sight-word instruction, word-analysis instruction, and oral reading error-correction. The research indicates that (a) among the sight-word instruction methods, those that use picture integration, constant delay, and the Edmark errorless discrimination methods seem strongest; (b) word-analysis instruction is a viable option for many students with moderate mental retardation; and (c) word analysis is the most effective method of oral reading-error correction. Suggestions for research and practice were discussed.

Aptitude by treatment interactions in computer-assisted word learning by mentally retarded students.

In previous research, tasks involving stimulus discrimination and simple learning were related to computer-assisted sight-word learning by moderately retarded adolescents (Conners & Detterman, 1987). The authors suggested that if these abilities interacted with specific instructional variables to determine word learning, such interactions might be useful in designing individualized computer-assisted instruction for mentally retarded students. In the present study interactions of these two abilities with two specific instructional variables were investigated. An interaction was found between stimulus discrimination and the number of words presented at one time for learning. Results were interpreted within Anderson's (1982) model of declarative and procedural knowledge.

Information-processing correlates of computer-assisted word learning by mentally retarded students.

Information-processing correlates of computer-assisted word learning by moderately and severely mentally retarded students were identified. Nineteen subjects completed 10, 15-minute computer-assisted instruction sessions and seven basic cognitive tasks measuring simple learning, choice reaction time, relearning, probed recall, stimulus discrimination, tachistoscopic threshold, and recognition memory. Stimulus discrimination, probed recall, and simple learning were significantly related to word learning. Results suggest that instruction should be modified to accommodate individual differences in these abilities.