A multiple case study of verbal short-term memory in velo-cardio-facial syndrome

Background Velo‐cardio‐facial syndrome (VCFS, 22q11.2 deletion) is characterized by severely delayed language development. The current study explored the integrity of verbal short‐term memory (STM), a cognitive function critically involved in language development, in eight children with VCFS. Methods Using a multiple case study design, we presented a series of STM tasks exploring immediate serial recall for word and non‐word lists to eight children with VCFS (aged 8–12 years) and to chronological‐age‐matched control groups. A first task assessed the integrity of phonological coding in verbal STM by comparing recall for phonologically similar and dissimilar words. Subsequently, the interaction between verbal knowledge and STM capacity was investigated by comparing recall for high‐ and low‐imageability words, for high‐ and low‐frequency words, and for words and non‐words. A final task assessed short‐term serial order recognition for digit sequences. Results When computing the number of items recalled in the word recall tasks, independently of their serial position, only one child presented consistent difficulties. Short‐term recall of non‐words was normal in each child. Phonological similarity and verbal knowledge influenced STM performance to a similar extent in children with VCFS and controls. On the other hand, when applying a strict serial recall criterion, difficulties with the word and non‐word recall tasks were observed in most children. Half of the patients were also impaired in the serial order recognition task. Conclusions Despite mild intellectual disability, it is possible for short‐term retention capacities for verbal item information to be at an age‐appropriate level in VCFS. However, STM for serial order information could be impaired more specifically.     

A comparison of oral narratives in children with specific language and non-specific language impairment

This research investigated whether children with specific language impairment (SLI) and non-specific language impairment (NLI) could be differentiated by their oral narrative characteristics. Oral narrative samples were collected from 69 children and comparisons were made among four groups of participants. The two language impairment groups (SLI and NLI), aged 4;11–6;03, were matched for age and their linguistics skills. Their oral narratives were compared between these diagnostic groups and with age-matched and language-matched control groups. Measures of narrative structure, cohesion, and information did not significantly differentiate the SLI and NLI groups, suggesting that the influence of their similar linguistic skills on oral narrative measures was stronger than the influence of their differing non-verbal cognition. The SLI group produced significantly more complex and informative oral narratives than the language-matched group, while the NLI group differed from the language-matched group on fewer measures. Interactions among linguistic, cognitive, maturational, and task factors are discussed.     

Memory consolidation in children with specific language impairment: Delayed gains and susceptibility to interference in implicit sequence learning

In this study, the time course of the procedural learning of a visuomotor sequence skill was followed over a 24-hour and a 1-week time period in children with and without specific language impairment (SLI). Two aspects of memory consolidation in implicit sequence learning were examined: the evolution of post-training gains in sequence knowledge (Experiment 1) and the susceptibility to interference (Experiment 2). In the first experiment, 18 children with SLI and 17 control children matched for sex, age, and nonverbal intelligence completed a serial reaction-time (SRT) task and were tested 24 hours and 1 week after practicing. The two groups of children attained an equal level of sequence knowledge in the training session, but the children with SLI lacked the consolidation gains displayed by the control children in the two post-training sessions. Working with a new group of children, 17 with SLI and 17 control peers, Experiment 2 examined resistance to interference by introducing a second sequence 15 min after the first training session. Similar results were obtained for the performance of both groups in the training session. However, although the performance of the control group improved in the post-training sessions, the performance of the SLI group deteriorated significantly during the consolidation phase due to the interfering sequence. These findings suggest that the consolidation phase of sequence learning is impaired in children with SLI.     

Phonological memory and word learning deficits in children with specific language impairment: A role for perceptual context?

BackgroundSensitivity to perceptual context (anchoring) has been suggested to contribute to the development of both oral- and written-language skills, but studies of this idea in children have been rare.AimsTo determine whether deficient anchoring contributes to the phonological memory and word learning deficits of children with specific language impairment (SLI).Methods and procedures84 preschool children with and without SLI participated in the study. Anchoring to repeated items was evaluated in two tasks – a phonological memory task and a pseudo-word learning task.Outcomes and resultsCompared to children with typical development, children with SLI had poorer phonological memory spans and learned fewer words during the word learning task. In both tasks the poorer performance of children with SLI reflected a smaller effect of anchoring that was manifested in a smaller effect of item repetition on performance. Furthermore, across the entire sample anchoring was significantly correlated with performance in vocabulary and grammar tasks.Conclusions and implicationsThese findings are consistent with the hypothesis that anchoring contributes to language skills and that children with SLI have impaired anchoring, although further studies are required to determine the role of anchoring in language development.     

Non-word repetition in children with specific language impairment: a deficit in phonological working memory or in long-term verbal knowledge?

In this study we investigated the effects of long-term memory (LTM) verbal knowledge on short-term memory (STM) verbal recall in a sample of Italian children affected by different subtypes of specific language impairment (SLI). The aim of the study was to evaluate if phonological working memory (PWM) abilities of SLI children can be supported by LTM linguistic representations and if PWM performances can be differently affected in the various subtypes of SLI. We tested a sample of 54 children affected by Mixed Receptive-Expressive (RE), Expressive (Ex) and Phonological (Ph) SLI (DSM-IV - American Psychiatric Association, 1994) by means of a repetition task of words (W) and non-words (NW) differing in morphemic structure [morphological non-words (MNW), consisting of combinations of roots and affixes - and simple non-words - with no morphological constituency]. We evaluated the effects of lexical and morpho-lexical LTM representations on STM recall by comparing the repetition accuracy across the three types of stimuli. Results indicated that although SLI children, as a group, showed lower repetition scores than controls, their performance was affected similarly to controls by the type of stimulus and the experimental manipulation of the non-words (better repetition of W than MNW and NW, and of MNW than NW), confirming the recourse to LTM verbal representations to support STM recall. The influence of LTM verbal knowledge on STM recall in SLI improved with age and did not differ among the three types of SLI. However, the three types of SLI differed in the accuracy of their repetition performances (PMW abilities), with the Phonological group showing the best scores. The implications for SLI theory and practice are discussed.     

Novel-word learning deficits in Mandarin-speaking preschool children with specific language impairments

Children with SLI exhibit overall deficits in novel word learning compared to their age-matched peers. However, the manifestation of the word learning difficulty in SLI was not consistent across tasks and the factors affecting the learning performance were not yet determined. Our aim is to examine the extent of word learning difficulties in Mandarin-speaking preschool children with SLI, and to explore the potent influence of existing lexical knowledge on to the word learning process. Preschool children with SLI (n = 37) and typical language development (n = 33) were exposed to novel words for unfamiliar objects embedded in stories. Word learning tasks including the initial mapping and short-term repetitive learning were designed. Results revealed that Mandarin-speaking preschool children with SLI performed as well as their age-peers in the initial form-meaning mapping task. Their word learning difficulty was only evidently shown in the short-term repetitive learning task under a production demand, and their learning speed was slower than the control group. Children with SLI learned the novel words with a semantic head better in both the initial mapping and repetitive learning tasks. Moderate correlations between stand word learning performances and scores on standardized vocabulary were found after controlling for children's age and nonverbal IQ. The results suggested that the word learning difficulty in children with SLI occurred in the process of establishing a robust phonological representation at the beginning stage of word learning. Also, implicit compound knowledge is applied to aid word learning process for children with and without SLI. We also provide the empirical data to validate the relationship between preschool children's word learning performance and their existing receptive vocabulary ability.     

Short-term memory and vocabulary development in children with Down syndrome and children with specific language impairment

A longitudinal comparison was made between development of verbal and visuo-spatial short-term memory and vocabulary in children with Down syndrome (DS), children with specific language impairment (SLI), and typically developing children as a control group. Participants were 12 children with DS (6 males, 6 females; mean chronological age 9y 9mo [SD 2.8 mo], range 8y 6mo to 11y 4mo); nine children with SLI (4 males, 5 females; mean chronological age 3y 9mo [SD 4.8mo], range 3y 3mo to 4y 5mo); and 12 typically developing children (5 males, 7 females; mean chronological age 4y 4mo [SD 3.9mo], range 3y 3mo to 4y 3mo). Participants were matched on mental age (mean mental age 4y 3mo). All participants completed verbal short-term memory, visuo-spatial short-term memory, and expressive and receptive vocabulary tasks on three occasions over 1 year. Similarities were seen in the clinical groups for verbal short-term memory. There was some evidence of difficulty in visuo-spatial short-term memory in the children with SLI relative to the other groups, but all three groups showed overlap in visuo-spatial short-term memory performance. At the final time-point vocabulary performance in the clinical groups was similar; the typically developing children showed higher vocabulary abilities than both clinical groups.     

Visuospatial support for verbal short-term memory in individuals with Down syndrome

Individuals with Down syndrome (DS) tend to have impaired verbal short-term memory (STM), which persists even when visual support is provided for carrying out verbal tasks. Objective: The current study aims to investigate whether visuospatial support, rather than just visual, can compensate for verbal STM deficits in these individuals. The performance of 25 children and adolescents with DS (mean age = 12.5, SD = 3.8) on five word span tasks was compared with that of two groups of typically developing children, matched for mental age (N = 25; mean age = 6.0, SD = .2) and for receptive vocabulary (N = 25; mean age = 4.0, SD = .8). Four of the five tasks varied in terms of input and output - verbal and/or visual - and the fifth task included a spatial component in addition to visual input and output. DS individuals performed equally bad in the pure verbal task and in those with visual components; however, there was a significant improvement when the spatial component was included in the task. The mental age matched group outperformed DS individuals in all tasks except for that with the spatial component; the receptive vocabulary matched group, outperformed DS individuals only in the pure verbal task. We found that visuospatial support improves verbal STM in individuals with DS. This result may have implications for intervention purposes.     

Verbal short-term memory in individuals with chromosome 22q11.2 deletion: specific deficit in serial order retention capacities?

Many researchers have recently explored the cognitive profile of velocardiofacial syndrome (VCFS), a neurodevelopmental disorder linked to a 22q11.2 deletion. However, verbal short-term memory has not yet been systematically investigated. We explored verbal short-term memory abilities in a group of 11 children and adults presenting with VCFS and two control groups, matched on either CA or vocabulary knowledge, by distinguishing short-term memory for serial order and item information. The VCFS group showed impaired performance on the serial order short-term memory tasks compared to both control groups. Relative to the vocabulary-matched control group, item short-term memory was preserved. The implication of serial order short-term memory deficits on other aspects of cognitive development in VCFS (e.g., language development, numerical cognition) is discussed.     

The developmental neural substrates of Hebb repetition learning and their link with reading ability

Hebb repetition learning is a fundamental learning mechanism for sequential knowledge, such as language. However, still little is known about its development. This fMRI study examined the developmental neural substrates of Hebb repetition learning and its relation with reading abilities in a group of 49 children aged from 6 to 12 years. In the scanner, the children carried out an immediate serial recall task for syllable sequences of which some sequences were repeated several times over the course of the session (Hebb repetition sequences). The rate of Hebb repetition learning was associated with modulation of activity in the medial temporal lobe. Importantly, for the age range studied here, learning‐related medial temporal lobe modulation was independent of the age of the children. Furthermore, we observed an association between regular and irregular word reading abilities and the neural substrates of Hebb repetition learning. This study suggests that the functional neural substrates of Hebb repetition learning do not undergo further maturational changes in school age children, possibly because they are sustained by implicit sequential learning mechanisms which are considered to be fully developed by that age. Importantly, the neural substrates of Hebb learning remain significant determinants of children's learning abilities, such as reading.     

Analogical mapping across modalities in children with specific language impairment (SLI)

Analogical mapping is a domain-general cognitive process found in language development, and more particularly in the abstraction of construction schemas. Analogical mapping is considered as the general cognitive process which consists in the alignment of two or several sequences in order to detect their common relational structure and generalize it to new items. The current study investigated analogical mapping across modalities in children with specific language impairment (SLI). Nineteen children with SLI and their age-matched peers were administered two tasks: a linguistic analogical reasoning task (composed of syllables) and a similar non-linguistic analogical reasoning task (composed of pictures). In the two tasks, the items presented were divided into two groups: items with perceptual cues and items without perceptual cues. Children had to complete a sequence sharing the same relational structure as previously presented sequences. Results showed an expected group effect with poorer performance for children with SLI compared to children with typical language development (TLD). Results corroborate hypotheses suggesting that children with SLI have difficulties with analogical mapping, which may hinder the abstraction of construction schemas. Interestingly, whereas no interaction effect between group and modality (linguistic vs. non-linguistic) was revealed, a triple interaction Group * Modality * Perceptual support was observed. In the non-linguistic task, the performance of children with SLI was the same for items with and without perceptual clues, but in the linguistic task they performed more poorly for items without perceptual cues compared to items with perceptual cues. The results and limits of the study are discussed.     

Visual-spatial processing in children and adolescents with Down's syndrome: a computerized assessment of memory skills

Background Several studies have identified better visual‐spatial than verbal memory skills in children with Down's syndrome (DS); however, research in both typical development and DS points to a relative dissociation between visual and spatial memory processing, questioning the notion of a unitary visual‐spatial memory construct. The insufficient and often contradictory results regarding the visual‐spatial memory domain probably reflect the heterogeneity of memory tests employed by these studies and the different memory systems that they evaluate. Method We administered five visual‐spatial memory tasks from the Cambridge Neuropsychological Test Automated Battery (CANTAB) to 25 children with DS and to 25 controls matched for mental age (MA) and basic psychomotor speed and accuracy. The memory tasks measure spatial span, visual and spatial recognition, paired associates learning and self‐ordered search abilities. Results The results confirm the relative sparing of the spatial short‐term memory (STM) capacity in children with DS; however, as memory load increases, in recognition tasks, or when visual and spatial demands are combined, their performance is impaired compared with MA controls. The same impairment is generated by additional executive demands in the self‐ordered search task, although search strategy is similar to the one presented by MA controls. Conclusions We did not find support for a visual vs. spatial dissociation in recognition memory. Performance impairment in the visual‐spatial domain parallels the increase in working memory (WM) load or in the executive demands of the task. Possible neurobiological implications of the observed performance on the CANTAB tasks are also considered.     

The developmental neural substrates of item and serial order components of verbal working memory

Behavioral and developmental studies have made a critical distinction between item and serial order processing components of verbal working memory (WM). This functional magnetic resonance imaging (fMRI) study determined the extent to which item and serial order WM components are characterized by specialized neural networks already in young children or whether this specialization emerges at a later developmental stage. Total of 59 children aged 7–12 years performed item and serial order short‐term probe recognition tasks in an fMRI experiment. While a left frontoparietal network was recruited in both item and serial order WM conditions, the right intraparietal sulcus was selectively involved in the serial order WM condition. This neural segregation was modulated by age, with both networks becoming increasingly separated in older children. Our results indicate a progressive specialization of networks involved in item and order WM processes during cognitive development.     

A Normed Study of Face Recognition in Autism and Related Disorders

Although the interpretation of studies of face recognition in older children, adolescents, and adults with autism is complicated by the fact that participating samples and adopted methodologies vary significantly, there is nevertheless strong evidence indicating processing peculiarities even when task performance is not deficient. Much less is known about face recognition abilities in younger children with autism. This study employed a well-normed task of face recognition to measure this ability in 102 young children with autism, pervasive developmental disorder not otherwise specified (PDDNOS), and non-PDD disorders (mental retardation and language disorders) matched on chronological age and nonverbal mental age, and in a subsample of 51 children divided equally in the same three groups matched on chronological age and verbal mental age. There were pronounced deficits of face recognition in the autistic group relative to the other nonverbally matched and verbally matched groups. Performance on two comparison tasks did not reveal significant differences when verbal ability was adequately controlled. We concluded that young children with autism have face recognition deficits that cannot be attributed to overall cognitive abilities or task demands. In contrast to controls, there was a lower correlation between performance on face recognition and nonverbal intelligence, suggesting that in autism face recognition is less correlated with general cognitive capacity. Contrary to our expectation, children with PDDNOS did not show face recognition deficits.     

Phonological learning in semantic dementia

Patients with semantic dementia (SD) have anterior temporal lobe (ATL) atrophy that gives rise to a highly selective deterioration of semantic knowledge. Despite pronounced anomia and poor comprehension of words and pictures, SD patients have well-formed, fluent speech and normal digit span. Given the intimate connection between phonological STM and word learning revealed by both neuropsychological and developmental studies, SD patients might be expected to show good acquisition of new phonological forms, even though their ability to map these onto meanings is impaired. In contradiction of these predictions, a limited amount of previous research has found poor learning of new phonological forms in SD. In a series of experiments, we examined whether SD patient, GE, could learn novel phonological sequences and, if so, under which circumstances. GE showed normal benefits of phonological knowledge in STM (i.e., normal phonotactic frequency and phonological similarity effects) but reduced support from semantic memory (i.e., poor immediate serial recall for semantically degraded words, characterised by frequent item errors). Next, we demonstrated normal learning of serial order information for repeated lists of single-digit number words using the Hebb paradigm: these items were well-understood allowing them to be repeated without frequent item errors. In contrast, patient GE showed little learning of nonsense syllable sequences using the same Hebb paradigm. Detailed analysis revealed that both GE and the controls showed a tendency to learn their own errors as opposed to the target items. Finally, we showed normal learning of phonological sequences for GE when he was prevented from repeating his errors. These findings confirm that the ATL atrophy in SD disrupts phonological processing for semantically degraded words but leaves the phonological architecture intact. Consequently, when item errors are minimised, phonological STM can support the acquisition of new phoneme sequences in patients with SD.     

Implicit and explicit memory functioning in children with heavy prenatal alcohol exposure.

Prenatal alcohol exposure is associated with widespread and devastating neurodevelopmental deficits. Numerous reports have suggested memory deficits in both humans and animals exposed prenatally to alcohol. However, the nature of these memory deficits remains to be characterized. Recently children with fetal alcohol syndrome were shown to have learning and memory deficits on a verbal learning and memory measure that involved free recall and recognition memory. The current study seeks to further characterize memory functioning in children with heavy prenatal alcohol exposure by evaluating priming performance. The choice of task is also relevant given previous studies of memory performance in patient groups with and without involvement of the basal ganglia, a group of structures known to be affected in fetal alcohol syndrome. Three groups were evaluated for lexical priming, free recall, recognition memory, and verbal fluency: (1) children with heavy prenatal alcohol exposure; (2) children with Down syndrome; and (3) nonexposed controls. The children with Down syndrome showed significantly less priming than alcohol-exposed children, who did not differ from controls. In addition, the alcohol-exposed children were impaired on the free recall task but not on the recognition memory task, whereas the children with Down syndrome performed significantly worse than the alcohol-exposed group on both tasks. Finally, on the verbal fluency task, children with heavy prenatal alcohol exposure were impaired on both category and letter fluency, but the degree of impairment was greater for letter fluency. These results further characterize the memory deficits in children with heavy prenatal alcohol exposure suggesting that in spite of learning and memory deficits, they are able to benefit from priming of verbal information.     

Short-term and serial memory in autistic,retarded, and normal children

Experimental data on memory ability of autistic children is scarce and contradictory. It is suggested that this may in part be the result of failure to control for acquisition of the correct response before memory is tested. In the first experiment reported, acquisition was controlled in a delayed-response visual discrimination task. The performance of autistic children was compared with MA matched normal and retarded controls. Recall deteriorated with increasing delay interval in each group. There were no significant group differences. The second experiment was designed to measure the effects of interference on memory using a serial memory task. No differences were found among groups in rate of learning, although the autistic children improved significantly on the second and longer series. There was no relationship between performance on the STM and the serial memory tasks over the same time intervals for any group. The results are interpreted as supporting the view that when MA and response acquisition level are equated with normal and retarded children in a memory task, autistic children do not show any specific memory deficits.     

Non-word Repetition Impairment in Autism and Specific Language Impairment: Evidence for Distinct Underlying Cognitive Causes

Language-impaired individuals with autism perform poorly on tests such as non-word repetition that are sensitive clinical markers of specific language impairment (SLI). This has fuelled the theory that language impairment in autism represents a co-morbid SLI. However, the underlying cause of these deficits may be different in each disorder. In a novel task, we manipulated non-word stimuli in three ways known to influence the repetition accuracy of children with SLI. Participants with SLI were affected differently by these manipulations to children with autism. Children with autism performed similarly to language-matched typical children in terms of levels and patterns of performance, and types of error made, suggesting that the underlying cognitive cause of non-word repetition deficits is different in each disorder.     

Comorbid motor deficits in a clinical sample of children with specific language impairment

The aim of the present study was to compare the motor function of a clinical sample of children with specific language impairment (SLI) to a language-matched comparison group that had not been referred for SLI assessment. A typical language comparison group with similar nonverbal IQ was also included. There were approximately 35 children in each group, aged 9- to 10-years-old, and the children completed a range of standardised language, motor and literacy measures. The results showed that the SLI group scored significantly lower than the language-matched and typical language comparison groups on all of the motor and literacy measures. We conclude that language factors alone are insufficient to explain the extensive comorbid motor and literacy deficits shown by the children with SLI in this study. We suggest that the clinical diagnosis of SLI may be influenced by the presence of additional developmental difficulties, which should be made explicit in assessment procedures, and that intervention strategies, which address the broad range of difficulties experienced by children with a clinical diagnosis of SLI, should be prioritised.     

Short term memory and working memory in blind versus sighted children

There is evidence that blind people may strengthen their memory skills to compensate for absence of vision. However, which aspects of memory are involved is open to debate and a developmental perspective is generally lacking. In the present study, we compared the short term memory (STM) and working memory (WM) of 10-year-old blind children and sighted children. STM was measured using digit span forward, name learning, and word span tasks; WM was measured using listening span and digit span backward tasks. The blind children outperformed their sighted peers on both STM and WM tasks. The enhanced capacity of the blind children on digit span and other STM tasks confirms the results of earlier research; the significantly better performance of the blind children relative to their sighted peers on verbal WM tasks is a new interesting finding. Task characteristics, including the verbal nature of the WM tasks and strategies used to perform these tasks, are discussed.