Silvia Lanfranchi

Executive function in adolescents with Down Syndrome.

BACKGROUND The present work is aimed at analysing executive function (EF) in adolescents with Down Syndrome (DS). So far, EF has been analysed mainly in adults with DS, showing a pattern of impairment. However, less is known about children and adolescents with this syndrome. Studying adolescents with DS might help us better understand whether performances on EF tasks of individuals with DS are determined by age or by Alzheimer disease, as some studies suggest, or whether their performances are directly related to DS cognitive profile. METHOD A battery of EF tasks assessing set shifting, planning/problem-solving, working memory, inhibition/perseveration and fluency, as well as a tasks assessing sustained attention has been administered to a group of 15 adolescents with DS and 15 typically developing children matched for mental age. All EF tasks were selected from previous studies with individuals with intellectual disabilities or from developmental literature and are thought to be useful for the samples considered. RESULTS The present results revealed that the group of individuals with DS performed at a significantly lower level on tasks assessing set shifting, planning/problem-solving, working memory and inhibition/perseveration, but not on the tasks assessing fluency. In addition, individuals with DS demonstrated a greater number of errors and less strategy use for the sustained attention task. CONCLUSIONS The results suggest a broad impairment in EF in adolescents with DS, and are consistent with several similar studies conducted with adults with DS. We assume that EF deficit is a characteristic of DS.

Verbal and Visuospatial Working Memory Deficits in Children With Down Syndrome

The hypothesis that deficits of children with Down syndrome on working memory tasks are more evident the higher the control required and for verbal than visuospatial tasks was tested. Two groups of children, one with Down syndrome, who ranged in age from 7 to 18, and a control group were assessed with batteries of verbal and visuospatial working memory tests requiring different levels of control. On tasks requiring low control, children with Down syndrome showed impairment of verbal but not visuospatial working memory tasks. As the requirement for control increased, they showed greater impairment on both tasks. Children with Down syndrome were comparatively better in visuospatial than verbal tasks. Implications of these results for working memory models and the role of working memory in intelligence were discussed.

Domain-Specific and Domain-General Precursors of Mathematical Achievement: A Longitudinal Study from Kindergarten to First Grade.

BACKGROUND Many contributing factors, both domain specific and domain general, influence childrens performance in school achievement. AIMS This research aims to verify the importance of kindergarten measures of cognitive abilities and numerical competence in the role of predicting mathematical school achievement at the end of first grade. SAMPLE AND METHODS A total of 70 children (38 females and 32 males) took part in the study. We tested the children at the beginning of their last year of kindergarten (time 1) on the following cognitive abilities: IQ, phonology, counting skills, verbal short-term memory, visuo-spatial short-term memory, working memory, and processing speed. Then, we tested the same children at end of their last year of kindergarten (time 2) on a measure of numerical competence and at the end of their first year of primary school (time 3) on a test of math achievement. RESULTS Path analysis models revealed the direct influence of working memory and processing speed on predicting numerical competence in pre-schoolers and the influence of processing speed and verbal IQ on predicting math achievement in first graders. Moreover, this study found a direct link between numerical competence and math achievement. CONCLUSIONS Both domain-specific and domain-general factors contribute to determining math achievement at the end of first grade.

Working memory in individuals with fragile X syndrome

The present research tests the hypothesis that fragile X syndrome (FXS) is associated with a deficit in working memory (WM) and the deficit is more pronounced the higher the control requirements of the task. To this purpose, 15 boys with FXS and 15 typically developing children, matched for mental age, assessed with Logical Operation Test, were tested with batteries of 4 verbal and 4 visuospatial WM tasks requiring different levels of control. Children with FXS showed a performance equal to controls, in WM tasks requiring low and medium-low control but significant impairment in correspondence with greater control requirements. Results show that boys with FXS present a WM deficit only when high control is required by the task, supporting the hypothesis that control can be a critical variable distinguishing WM functions and explaining intellectual differences. On the contrary the hypothesis that the FXS is associated with a visuospatial deficit was not supported.

Working Memory and Cognitive Skills in Individuals with Down Syndrome

This work is aimed at analyzing working memory (WM) components and their relationships with other cognitive processes in individuals with Down syndrome (DS). Particular attention is given to examine whether a verbal WM deficit is due to difficulties in verbal abilities often showed by individuals with DS, or whether it is a deficit per se. A group of 20 individuals with DS was compared to a group of 20 typically developing (TD) children matched on vocabulary comprehension and to a group of 20 TD children matched on general verbal intelligence. The groups received a battery of 3 verbal and 3 visuospatial WM tasks requiring different degrees of control, and tests assessing verbal abilities (WPPSI verbal scale, PPVT), nonverbal skills (WPPSI performance scale), and logical thinking (LO). The results revealed that individuals with DS have deficits in both central executive (control) and verbal components of the WM system, and the latter one is independent of the general verbal abilities deficit. The data suggest that the development of central executive proceeds at a slower rate in individuals with DS and differently from TD children with comparable verbal abilities. The performance of individuals with DS on high-control WM tasks requires additional general resources that are strictly linked to intelligence.

Working memory in Down syndrome: is there a dual task deficit?

BACKGROUND Recent studies have shown that individuals with Down syndrome (DS) are poorer than controls in performing verbal and visuospatial dual tasks. The present study aims at better investigating the dual task deficit in working memory in individuals with DS. METHOD Forty-five individuals with DS and 45 typically developing children matched for verbal mental age completed a series of verbal and visuospatial working memory tasks, involving conditions that either required the combination of two tasks in the same modality (verbal or visual) or of cross-modality pairs of tasks. RESULTS AND CONCLUSIONS Two distinct deficits were found in individuals with DS: impairment in verbal tasks and further impairment in all dual task conditions. The results confirm the hypothesis of a central executive impairment in individuals with DS.

Inhibitory mechanisms in Down syndrome: Is there a specific or general deficit?

The cognitive profile of individuals with Down syndrome (DS) is known to be characterized by an impaired executive functioning, but inhibition-related processes have not been extensively examined in this setting. The aim of the present study was to investigate whether individuals with DS have any specific or general deficit in inhibitory processes. Tasks measuring prepotent response inhibition (the animal Stroop test), proactive interference (proactive interference task and intrusion errors), and response to distracters (directed forgetting task) were administered together with a working memory test to 19 individuals with DS and 19 typically developing (TD) children matched for mental age. Confirming previous findings, our results showed that the DS group performed less well in a verbal working memory task than the TD children. Analyzing our findings for the three inhibitory tasks yielded a picture of the DS children having a generalized difficulty in suppressing information that is irrelevant, or no longer relevant, to the goals of the task. These results suggest that DS is related not to specific, but rather to generalized inhibitory difficulties.

The effect of configuration on VSWM performance of Down syndrome individuals

BACKGROUND Recent studies have demonstrated that individuals with Down syndrome (DS) are poorer than controls in spatial-simultaneous tasks, but not in spatial-sequential tasks. To explain this finding, it has been suggested that the simultaneous visuo-spatial working memory deficit of individuals with DS could be due to the request for processing more than one item at a time. The present study examines the possibility of reducing the difficulties encountered by DS individuals on spatial-simultaneous tasks by proposing a task that uses structured material. METHOD Two tasks were administered to 20 children and adolescents with DS, and 20 controls matched for verbal mental age. The tasks involved memorising and recalling filled-cell positions in a series of matrices in which an increasing number of cells (1-7) were filled. In the structured condition the filled cells were displayed to form a pattern, whereas in the random condition they were randomly arranged. RESULTS AND CONCLUSIONS Results showed that individuals with DS are able to take advantage of structured material for raising their performance, but to a less extent than typically developing children.

Enumeration skills in Down syndrome

Individuals with Down syndrome (DS) exhibit various math difficulties which can be ascribed both to global intelligence level and/or to their atypical cognitive profile. In this light, it is crucial to investigate whether DS display deficits in basic numerical skills. In the present study, individuals with DS and two groups of typically developing (TD) children matched for mental and chronological age completed two delayed match-to-sample tasks in order to evaluate the functioning of visual enumeration skills. Children with DS showed a specific deficit in the discrimination of small numerosities (within the subitizing range) with respect to both mental and chronological age matched TD children. In contrast, the discrimination of larger numerosities, though lower than that of chronological age matched controls, was comparable to that of mental age matched controls. Finally, counting was less fluent but the understanding of cardinality seemed to be preserved in DS. These results suggest a deficit of the object tracking system underlying the parallel individuation of small numerosities and a typical - but developmentally delayed - acuity of the approximate number system for discrimination of larger numerosities.

The effectiveness of working memory training with individuals with intellectual disabilities – a meta-analytic review

Working memory (WM) training has been increasingly popular in the last years. Previous studies have shown that individuals with intellectual disabilities (ID) have low WM capacity and therefore would benefit by this type of intervention. The aim of this study was to investigate the effect of WM and cognitive training for individuals with ID. The effects reported in previous studies have varied and therefore a meta-analysis of articles in the major databases was conducted. Inclusion criteria included to have a pretest–posttest design with a training group and a control group and to have measures of WM or short-term memory. Ten studies with 28 comparisons were included. The results reveal a significant, but small, overall pretest–posttest effect size (ES) for WM training for individuals with ID compared to controls. A mixed WM approach, including both verbal and visuo-spatial components working mainly on strategies, was the only significant training type with a medium ES. The most commonly reported training type, visuo-spatial WM training, was performed in 60 percent of the included comparisons and had a non-significant ES close to zero. We conclude that even if there is an overall effect of WM training, a mixed WM approach appears to cause this effect. Given the few studies included and the different characteristics of the included studies, interpretations should be done with caution. However, different types of interventions appear to have different effects. Even if the results were promising, more studies are needed to better understand how to design an effective WM intervention for this group and to understand if, and how, these short-term effects remain over time and transfer to everyday activities.