Repetition priming in adults with Williams syndrome: age-related dissociation between implicit and explicit memory

We examined implicit and explicit memory in adults with Williams syndrome. An age-related dissociation was found; repetition priming (reflecting implicit memory) did not show change with age, but free recall (reflecting explicit memory) was markedly reduced. We also compared the performance of adults with Williams syndrome to adults with Down syndrome and those with unspecified mental retardation. A similar dissociation was observed in adults with Down syndrome but not in adults with unspecified mental retardation. An IQ-related dissociation was also found. Implicit and explicit memory, therefore, show different degrees of association with age and IQ, supporting theories of these memory processes. Results also suggest that Williams syndrome, similar to Down syndrome, may be associated with precocious aging, resulting in the loss of some cognitive abilities.     

Incidence and temporal patterns of adaptive behavior change in adults with mental retardation

The age-associated incidence of significant decline in adaptive behavior and the temporal pattern of decline in specific functional skill domains were examined in 646 adults with mental retardation through 88 years of age. Cumulative incidence of significant decline for adults with Down syndrome increased from less than.04 at age 50 to.67 by age 72, whereas cumulative incidence of significant decline for adults with mental retardation without Down syndrome increased from less than.02 at age 50 to.52 at age 88. Among adults experiencing overall decline, four clusters of behaviors were identified based upon the sequence and magnitude of changes, suggesting a pattern of loss not unlike that noted in the population without mental retardation with dementia.     

Implicit learning in children and adolescents with mental retardation

The literature on implicit learning in persons with mental retardation is scarce and contradictory with respect to the relationship between degree of intellectual disability and impact of implicit-learning processes on performance. We examined children and adolescents with mild or moderate mental retardation and typically developing children matched on MA with regard to their implicit learning. Individuals with mental retardation modified their behavior after an implicit training procedure in a way similar to MA- or CA-matched controls. The impact of implicit learning did not vary as a function of IQ or age. However, some differences appeared between groups in their explicit remembering of the training conditions. The theoretical implications of these results are discussed.     

Neuropsychological profiles of persons with mental retardation and dementia

This study examined the use of neuropsychological tests to assist in the differential diagnosis of dementia among persons with mental retardation. The author compared performances of persons with mental retardation and dementia (n = 10) to persons with mental retardation without dementia (n = 12). Participants were matched by IQ (mild or moderate mental retardation), age, presence of Down syndrome, and gender. In addition, all participants in the dementia group had corroborative medical tests (i.e., imaging, EEG, or high tau low AB42 protein testing) consistent with diagnosis of dementia. Test performance was compared on measures of attention and executive functions, language, memory and learning, and a dementia screening. Results from MANOVAs and nonparametric tests revealed significantly lower performance for persons with mental retardation and dementia in all areas assessed. Cut-off scores were also developed for the sample in order to maximize sensitivity and specificity for the test battery. Despite the small sample size, these findings suggest that there are significant measurable differences in several neurocognitive domains between the two groups.     

Implicit and explicit learning in young adults with mental retardation

We examined intelligence-related differences in explicit and implicit learning using an artificial grammar paradigm. Young adults with and without mental retardation completed a sequence-learning and identification task. For some participants, sequences were constructed following an artificial grammar; for others, sequences were random. Explicit learning was determined by ability to learn and later identify random sequences. Implicit learning was determined by the tendency to incorrectly identify new grammatical sequences as seen before, relative to new nongrammatical sequences. Participants with mental retardation did more poorly than participants without mental retardation on explicit learning but just as well on implicit learning. Results suggest that learning of complex materials, when accomplished through implicit processing, is functionally equivalent in individuals with and without mental retardation.     

Normal ageing in adults with Down's syndrome: a longitudinal study

The ubiquitous presence of the neuropathoiogy of Alzheimer disease (AD) in individuals with Down's syndrome (DS) over 40 years of age suggests that this group of people will exhibit a high prevalence of dementia of the Alzheimer type (DAT) as they age. The present study indicates that there is a clear discrepancy between the presumed presence of AD neuropathoiogy and the clinical expression of DAT among older people with DS. In the first 6 years of a longitudinal study, the present authors compared 91 adults (31–63 years of age) with DS and mild or moderate mental retardation to 64 adults (3 l –76 years of age) with other forms of mental retardation (MR) on yearly measures of mental status, short-and long-term memory, speeded psychomotor function, and visuospatial organization. The results indicated that, over repeated testing on the verbal long–term memory test, younger participants with DS showed small increases in their scores, while older participants with DS showed very slight decreases. Overall performance scores on this test and a speeded psychomotor task were poorer for both diagnostic groups in individuals aged SO years and older. The magnitude and type of these selective changes in performance were consistent with performance profiles observed in older healthy adults without mental retardation on tests measuring similar cognitive functions. Only four out of the 91 people with DS in the present sample showed changes in funaioning that have led to a diagnosis of possible DAT. and in these individuals, alternative causes of performance declines were concurrently present (e.g, thyroid dysfunction). These findings indicate that some age–associated changes in funaioning are related to ‘normal’ but probably precocious ageing among adults with DS. Furthermore, these findings suggest that adults with DS and mild or moderate mental retardation may be at lower risk for dementia during their fourth and fifth decades of life than previous studies have suggested.     

Maladaptive behaviors related to adaptive decline in aging adults with mental retardation

Changes in patterns of maladaptive behavior related to age-associated adaptive declines were investigated in 529 adults with mental retardation. Although individuals with no significant adaptive decline displayed stable patterns of maladaptive behavior over a 3-year period, those with declines in function showed more variable patterns. Certain maladaptive behaviors were related to the onset of adaptive declines, with some becoming of increasing concern even before adaptive declines were noted (e.g., lack of boundaries). Other behaviors increased as adaptive declines developed (e.g., withdrawal). In general, findings suggest similarities in the course of age-associated dementia of adults with and without mental retardation and indicate that increases in selected areas of maladaptive behavior may be early indicators of concern for individuals at risk.     

Personal competence of institutionalized adult males with or without Down syndrome

The Personal Competence Profile was administered to 30 male adults with Down syndrome and 30 male adults without Down syndrome matched on age, IQ, and years of institutionalization. Down syndrome subjects rated higher on attention, calmness, and niceness but lower on sensation, language, and boldness. The results were consistent with the classical personality stereotype of Down syndrome and suggest the utility of using personal competence as a framework for studying behavioral aspects of mental retardation.     

Effects of age and IQ on adaptive behavior domains for children with autism

Researchers have examined adaptive behavior in autism, but few studies have looked for different patterns of adaptive skills according to age and intelligence. Domain scores from the Vineland Adaptive Behavior Scale (VABS) were compared in relation to age and Performance IQ for 72 children and adolescents with autism and 37 nonautistic children and adolescents with mental retardation. Age and IQ were positively related to each of the Vineland domains. Children with autism had lower scores in the socialization domain. An interaction was present between Performance IQ and group: With increasing IQ, children with autism showed smaller increases in social functioning than children with mental retardation. A similar trend was present for daily living skills. Results suggest that (a) the relationship between the two groups' adaptive behavior profiles is stable from preschool age through adolescence, and (b) increasing IQ is associated with less of an increase in certain adaptive skills for children with autism.     

Cognitive abilities in children with congenital muscular dystrophy: correlation with brain MRI and merosin status.

The aim of the study was to evaluate whether children with merosin-positive or merosin-deficient congenital muscular dystrophy (CMD) show any cognitive impairment and whether this is related to brain abnormalities on magnetic resonance imaging (MRI). Twenty-two patients (age range: 5.8-15.3 years) were assessed by the Wechsler Intelligence Scales. Twelve were merosin-positive and ten merosin-deficient. One child had severe mental retardation and could not be tested. The full scale IQ in the remaining 21 ranged from 51 to 134, the verbal IQ ranged from 78 to 136 and the performance from 51 to 136. Of the twelve children with normal merosin one had a mild delay (IQ < 75) and two were borderline (IQ 75-95). Of the ten children with merosin-deficiency, one showed severe mental retardation and could not be tested, one showed a mild delay and two had borderline results. While the children with merosin deficiency with the typical diffuse white matter changes on MRI had normal scores, the children who in addition had cerebellar hypoplasia had lower performance IQ. The child with cortical dysplasia had severe mental retardation. Our results suggest that the spectrum of cognitive abilities in CMD is very wide even within genetically homogeneous conditions.     

Phonological reading skills acquisition by children with mental retardation

Twenty children with mental retardation (MR), age 7-12, completed a phonological reading skills program over approximately 10 weeks. As a result of the instruction, they were better able to sound out learned and transfer words compared to a control group matched on age, IQ, nonword reading, language comprehension, and phonemic awareness. Final sounding out was predicted by beginning reading skill in both groups, by phonemic awareness and articulation speed in the control group only, and by general language ability in the instruction group only. Neither IQ nor verbal working memory correlated significantly with final sounding out ability in either group. It is suggested that the instruction succeeded in compensating for weaknesses in phonemic awareness and speech articulation, but favored those who had better language skills.     

Relationships amongst age,language and related skills in adults with Down syndrome

Studies into the effects of ageing on language in adults with Down syndrome (DS) have tended to rely on measures that lack sensitivity to change because they fail to explore across linguistic domains or rely on proxy reports. The study aim was to use measures of receptive and expressive language from studies of younger individuals with DS in exploring relationships across linguistic and associated skills, and age in young to older adults. Fifty-five adults (aged 19–58 years), 10 with a diagnosis of or signs of early stage Alzheimer's Disease (AD), provided data on measures of functioning associated with AD, non-verbal cognition, receptive language (which provided a measure of mental age), receptive and expressive language, and short term auditory and visual memory. The first order correlation between the measure of AD and CA was significant; but not when the 10 participants with AD were removed from the analysis. Significant negative correlations were obtained between CA and all other measures; small to large significant positive correlations were found amongst the other measures. Partial correlations were conducted to remove the potential effects of AD and IQ (the latter measured by a test of non-verbal cognition). Remaining significant correlations were between auditory short term memory and all other included measures, expressive language and all other included measures, and CA and auditory short term memory and expressive language. The results indicate that deterioration with age in this cross-sectional study was accounted for largely by the presence of AD. The exceptions were for auditory short term memory and expressive language. The findings may reflect an underlying deficit in auditory short term memory for adults with DS, as has been found in previous research of children and adolescents. The implications are discussed in terms of the importance of including comprehensive measures of receptive and expressive language and the need to account for the presence of AD in studies of cognitive decline associated with ageing in DS.     

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.     

The role of residential homelikeness in promoting community participation by adults with mental retardation

We tested the influence of (1) the homelike appearance of residences, (2) residential staff-members' attitudes about people with mental retardation and (3) Client IQ on the number of activities adults clients with mental retardation conducted in their community. We tested the hypothesis these three variables exerted their influence by promoting positive staff-member interactions with clients. This was assessed by measuring the duration of Staff-initiated Social Interactions with residential clients. In our initial path model, Residential Homelikeness, Positive Staff Attitudes and Client IQ had no significant direct effect on Community Activities. In the final model, however, Residential Homelikeness and Positive Staff Attitudes exerted a statistically significant influence on Staff-initiated Social Interactions with clients, which in turn, exerted a statistically significant influence on Community Activities. This model illustrated: (1) the nearly equal influence of Staff Attitudes and architectural characteristics on Staff-initiated Interactions; and (2) the role of Staff-initiated Interactions in mediating the influence of Residential Homelikeness on community participation by adults with developmental disabilities.     

Mental retardation and subnormality in a birth cohort of 12,000 children in Northern Finland

The occurrence of mental retardation and subnormality were investigated in a one-year birth cohort (N = 12,058) from two provinces in Northern Finland; 96% of the children were followed-up to the age of 14. Of these children 253 (2.2%) were unable to go to an ordinary school and 449 (3.8%) were attending an ordinary school in a class lower than that appropriate for their age. The cumulative incidence of severe mental retardation (IQ less than 50) was 7.4 per 1,000; for mild mental retardation (IQ 50 to 70), 5.5 per 1,000; and for mental subnormality (IQ 71 to 85), 13.4 per 1,000. The corresponding prevalence rates were 6.3, 5.6, and 13.7 per 1,000. The total cumulative incidence of children with IQ less than 86 was 27.0 per 1,000 and the prevalence 25.6 per 1,000. There were 39 cases with Down syndrome, 3.2 per 1,000.     

Effects of verbal elaborations on memory for sentences in adults with mental retardation

We examined the effects of verbal elaborations on memory for verbal material in adults with mental retardation and a control group of adults of normal intelligence. During acquisition, three types of sentences were presented that differed in elaboration of the subject-adjective relationship: a) non-elaborated base sentences; b) base sentences with arbitrary verbal elaborations; and c) base sentences with explanatory verbal elaborations that clarified the significance of the subject-adjective relationship. At test, we varied the retrieval context by presenting either base sentences alone or base sentences with the verbal elaborations. A three-alternative, forced-choice recognition procedure was used to test memory for the target adjectives. Results yielded a positive effect of retrieval support (elaborations present at study and test) on recognition performance for adults with mental retardation. These data imply that the retrieval context plays an important role in recognition memory for adults with mental retardation.     

Exploring the Flynn effect in mentally retarded adults by using a nonverbal intelligence test for children

Increases in the scores on IQ tests across generations have been called the Flynn effect (FE). One of the unresolved questions is whether the FE affects all subsamples of the intellectual ability distribution equally. The present study was aimed at determining the size of the FE in moderately mentally retarded individuals. A nonverbal intelligence test developed for children, the Snijders-Oomen Nonverbal Intelligence Test (SON), was administered to 32 retarded adults with a mental age of 3–6 years. Sixty-nine children with a biological age in the same range and with normal intelligence served as a comparison group. Both an older and a more recent version of the SON were presented to all participants in a counterbalanced order. The proportion of items answered correctly was taken as a measure of the dependent variable. It was found that a FE existed in both the group of children and in the group of retarded adults, but that the FE was largest in the latter group. The importance of not using obsolete test norms when diagnosing mental retardation was stressed, and possible causes of the Flynn effect were discussed.     

Investigation of amygdala volume in men with the fragile X premutation

Premutation fragile X carriers have a CGG repeat expansion (55 to 200 repeats) in the promoter region of the fragile X mental retardation 1 (FMR1) gene. Amygdala dysfunction has been observed in premutation symptomatology, and recent research has suggested the amygdala as an area susceptible to the molecular effects of the premutation. The current study utilizes structural magnetic resonance imaging (MRI) to examine the relationship between amygdala volume, CGG expansion size, FMR1 mRNA, and psychological symptoms in male premutation carriers without FXTAS compared with age and IQ matched controls. No significant between group differences in amygdala volume were found. However, a significant negative correlation between amygdala volume and CGG was found in the lower range of CGG repeat expansions, but not in the higher range of CGG repeat expansions.     

精神发育迟滞合并精神分裂症的临床研究

目的探讨精神发育迟滞（MR）合并精神分裂症的临床特点。方法 48例MR合并精神分裂症患者按智商（IQ）≥50和IQ≤49分为两组进行临床特征分析,并与48例智力正常的精神分裂症患者比较。结果 MR合并精神分裂症患者IQ≥50和IQ≤49两组间临床差异无显著性（P≥0.05）;MR合并精神分裂症组与正常智力精神分裂症组的一级症状[1]、逻辑推理障碍、妄想、情感平淡、思维贫乏的差异有显著性（P〈0.01或P〈0.05）。结论 MR合并精神分裂症一级症状明显减少,有助于临床鉴别。     

Second-order belief attribution in Williams syndrome: intact or impaired?

Second-order mental state attribution in a group of children with Williams syndrome was investigated. The children were compared to age, IQ, and language-matched groups of children with Prader-Willi syndrome or nonspecific mental retardation. Participants were given two trials of a second-order reasoning task. No significant differences between the Williams syndrome and Prader-Willi or mentally retarded groups on any of the test questions were found. Results contrast with the view that individuals with Williams syndrome have an intact theory of mind and suggest that in their attributions of second-order mental states, children with Williams syndrome perform no better than do other groups of children with mental retardation.