Biomedical subjects

Stefano Vicari

Publications and source records attributed to Stefano Vicari.

14 recordsLinked to original sources

PubMed2006

Implicit learning deficits in dyslexic adults: an fMRI study.

It is assumed that several neuropsychological impairments characterize the cognitive profile of individuals with developmental dyslexia (DD). Phonological and visual processing are often impaired as well as auditory processing, attention, and information processing speed. Although reports in the literature on implicit learning abilities are contradictory, recent neurological and physiological data suggest that these abilities are deficient in individuals with DD. To evaluate implicit learning we administered a classical version of the serial reaction time task (SRTT) related to sequence learning. Using functional magnetic resonance imaging we investigated brain activation patterns associated with implicit learning deficits in 14 adults with DD matched with 14 normal readers. SRTT results indicated the absence of implicit learning in the DD group and different activations between groups mainly in SMA, inferior parietal areas and cerebellar lobule 6. These results can be interpreted in the light of the different capacities for the two groups to build an internal model to guide movements. Further, they explain DD individuals' difficulty in domains not directly related to reading ability.

Adult↗

PubMed2006

Acquired amnesia in childhood: a single case study.

We report the case of C.L., an 8-year-old child who, following the surgical removal of an ependymoma from the left cerebral ventricle at the age of 4 years, developed significant difficulties in retaining day-to-day events and information. A thorough neuropsychological analysis documented in C.L. a severe anterograde amnesic syndrome, characterised by normal short-term memory, but poor performance on episodic long-term memory tests. In particular, C.L. demonstrated virtually no ability to recollect new verbal information several minutes after the presentation. As for semantic memory, C.L. demonstrated general semantic competencies, which, depending on the test, ranged from the level of a 6-year-old girl to a level corresponding to her actual chronological age. Finding a patient who, despite being severely impaired in the ability to recollect new episodic memories, still demonstrates at least partially preserved abilities to acquire new semantic knowledge suggests that neural circuits implicated in the memorisation of autobiographical events and factual information do not overlap completely. This case is examined in the light of growing literature concerned with the dissociation between episodic and semantic memory in childhood amnesia.

Amnesia, Anterograde↗

PubMed2006

Short-term memory deficits are not uniform in Down and Williams syndromes.

Neuropsychological investigation of the development of the mnesic function in mental retardation has primarily focused on evaluating short-term memory (STM). Studies have often documented a reduced verbal short-term memory span in individuals with mental retardation and with Down syndrome in particular, compared to groups of mental age-matched controls. However, recent evidence suggests that verbal short-term memory is not equally impaired in all individuals with mental retardation. Findings in children with Williams syndrome are particularly relevant in this regard. Also, data concerning STM for visual information suggest that visual-object and visual-spatial working memory may be differently compromised in people with mental retardation. In particular, individuals with Williams syndrome exhibit specific difficulties in visual-spatial but not in visual-object working memory tasks compared to typically-developing children matched for mental age. Instead, people with Down syndrome show reduced performance in both visual-spatial and visual-object tests. Taken together, these results reinforce the view that intellectual disability is not a unitary condition characterized by homogeneous slowness of cognitive development but a variety of conditions in which some cognitive functions may be more disrupted than others. The finding that the working memory deficit in individuals with Williams and Down syndrome may be qualitatively differentiated also supports the hypothesis that it is not simply a manifestation of general cognitive impairment but, rather, the expression of a specific deficit of a discrete cognitive ability.

Amnesia↗

PubMed2006

Laterality in persons with intellectual disability. I--do patients with trisomy 21 and Williams-Beuren syndrome differ from typically developing persons?

Persons with trisomy 21 (T21) and Williams-Beuren syndrome (WBS) have different brain abnormalities which may affect manual laterality. We assessed 45 persons with T21 and 34 with WBS (mean age 13) and 81 typically developing children (TD). Manual laterality was assessed with a fifteen-item task administered two times, and Bishop's card-reaching task. We found more left-handers in the T21 group compared to the other two groups. Inconsistent laterality was higher in the two groups with genetic diseases than in the TD group. For Bishop's test, both T21 and WBS participants were less right-oriented than the TD group. They displayed different response patterns in midline crossing when reaching for the cards, but did not display more midline crossing inhibition than the TD group. Is atypical handedness linked to specific genetic syndromes and, more specifically for persons with T21, to the trisomy of some of the genes?

Aging↗

PubMed2006

Motor development and neuropsychological patterns in persons with Down syndrome.

Neuropsychological research has permitted defining specific cognitive profiles among individuals with mental retardation (MR) of different etiology. Namely, the cognitive profile of people with Down syndrome (DS) is often reported to be characterized by a deficit in language abilities that usually exceed impairments in visual-spatial capacities. However, recent studies have demonstrated a more complex neuropsychological profile in this population, with atypical development in the cognitive and in the linguistic domain. This paper is dedicated to reviewing literature regarding motor, linguistic and cognitive abilities in DS. Our aim is to present evidences supporting the hypothesis that individuals with these syndrome exhibit a peculiar motor development and neuropsychological profile with some abilities more preserved and others more impaired. This finding may have theoretical and practical implications. In fact, a better definition of the cognitive pattern in DS may contribute to understand the nature of MR in general and, also, it may suggests individualized rehabilitation treatment protocols.

Child↗

PubMed2006

Laterality in persons with intellectual disability II. Hand, foot, ear, and eye laterality in persons with Trisomy 21 and Williams-Beuren syndrome.

Laterality (hand, foot, ear, and eye) was assessed in participants with Trisomy 21 (62) and Williams-Beuren syndrome (WBS) (39). Handedness was also assessed in a card reaching task. The comparison group included 184 typically developing persons. Two independent age sub-groups were formed: 7 to 10 years old and 11 to 34 years old. We confirmed previous data: individuals with T21 were more frequently left- or mixed-handed than typically developing persons; individuals with WBS had intermediate scores. The two groups with genetic disorders had less right foot preference. Manual and foot inconsistencies characterized both groups with genetic disorders. Cross hand-foot preference was lower in the typically developing group. Differences in IQ levels did not correlate with differences in laterality scores. Overall laterality profiles were not the same in the two groups with genetic disorders: the greatest differences were observed between typically developing persons and persons with Trisomy 21.

Adolescent↗

PubMed2006

Evidence from two genetic syndromes for the independence of spatial and visual working memory.

This study aimed at investigating the possible dissociation between visual-object and visual-spatial working memory (WM) in individuals with Williams syndrome (WS) and Down syndrome (DS). Four study groups were included: WS group (10 males, 5 females) with a mean chronological age (CA) of 19 years 8 months (SD 6y 1mo) and a mean mental age (MA)of 6 years 11 months (SD 1y 5mo); WS comparison group (7 males, 8 females) comprised of typically developing children with a mean CA of 6 years 10 months (SD 10mo) and a mean MA of 6 years 11 months (SD 8mo)matched as a group with the participants with WS on the basis of mental age; DS group (11 males, 7 females) with a mean CA of 15 years 10 months (SD 5y 8mo) and a mean MA of 5 years 2 months (SD 8mo); and DS comparison group (10 males, 8 females) with a mean CA of 5 years and 1 month (SD 7mo)and a mean MA of 5 years 2 months (SD 8mo) selected to match the DS group on the basis of mental age. They were all administered tests that explored visual perception (Visual Perception Test - Subtest 4 and Line Orientation tests), visual imagery (imaging the colour of objects and the tail length of well-known animals), spatial imagery (mental rotation of visually presented or verbally evoked objects), and WM for visual-object and visual-spatial information. Individuals with WS exhibited specific difficulties in the visual-spatial, but not the visual-object, WM task. Instead, people with DS showed reduced performance in both tests. However, whereas the observed deficit in individuals with DS persisted when perceptual abilities were taken into account, the deficit in individuals with DS was compensated when their scores were adjusted for performance on perceptual tasks. These results support the hypothesis of a dissociation within the sketch-pad slave system in the WM model and reinforce the view of intellectual disability as a non-unitary condition.

Adolescent↗

PubMed2005

Visual and spatial long-term memory: differential pattern of impairments in Williams and Down syndromes.

This purpose of this study was to investigate visual-object and visual-spatial long-term memory (LTM) abilities in individuals with Williams syndrome (WS) and Down syndrome (DS). Four groups comprised of 15 participants were included: WS group (10 males) with a mean chronological age (CA) of 18 years 5 months, SD 6 years 4 months, and mean mental age (MA) of 6 years 8 months, SD 1 year 5 months; WS control group (eight males) comprised of typically developing children (CA mean 6y 7mo, SD 8mo); DS group, (10 males, CA mean 16y 5mo, SD 5y 10mo; MA mean 5y 4mo, SD 8mo); and DS control group (seven males) formed by typically developing children (CA mean 5y 6mo, SD 7mo). In the WS and DS groups mental age and IQ were evaluated with the Form L-M of the Stanford-Binet Intelligence Scale. Results showed that individuals with WS showed decreased learning of visual-spatial material but substantially typical learning of visual-object patterns as compared to a group of mental-age-matched typically developing children. Individuals with DS showed the opposite profile, i.e. typical learning of visual-spatial sequences but impaired learning of visual-object patterns. These results, showing an interesting double dissociation between these two genetic syndromes in the learning of visual-object patterns as opposed to visual-spatial data, support the interpretation of learning disability* as a heterogeneous condition, characterized by potentially very different qualitative profiles of cognitive impairment.

Adolescent↗

PubMed2004

Neuropsychological profile of Italians with Williams syndrome: an example of a dissociation between language and cognition?

Important claims have been made regarding the contrasting profiles of linguistic and cognitive performance observed in two genetically based syndromes, Williams syndrome (WS) and Down syndrome (DS). Earlier studies suggested a double dissociation, with language better preserved than nonverbal cognition in children and adults with WS, and an opposite profile in children and adults with DS. More recent studies show that this initial characterization was too simple, and that qualitatively different patterns of deficit observed within both language and visual-spatial cognition, in both groups. In the present study, large samples of children and adolescents with WS and age-matched DS are compared with typically developing (TD) controls matched to WS in mental age, on receptive and expressive lexical and grammatical abilities, semantic and phonological fluency, digit span and nonverbal visual-spatial span, and on 2 visual-spatial construction tasks. Study 1 confirmed distinct profiles of sparing and impairment for the 2 groups, within as well as between language and nonlinguistic domains, even after IQ variations were controlled. In Study 2 we compared performance of the children, adolescents and young adults with DS and WS included in the first study, divided on the basis of the chronological age of the participants (under 8 years; over 12 years). Although it is important to stress that these are cross-sectional rather than longitudinal data, the results demonstrated that the profile of younger children is different in respect to those of the older children; initial states of the system cannot be inferred by the final state. Possible neural substrates for these profiles and trajectories are discussed.

Adolescent↗

PubMed2004

Reading and phonological awareness in Williams syndrome.

This article describes the relationship between reading, phonological awareness abilities (PA), and intelligence in a group of 16 individuals with Williams syndrome (WS) and in a group of 16 typically developing children, matched for mental age. The individuals with WS were impaired in passage comprehension, in some areas of PA investigated (syllable deletion and rhyme detection), and in nonword reading accuracy, a measure of grapheme-phoneme conversion. This latter finding is relevant, considering that in Italy regular print-to-sound correspondence is the most practiced teaching routine in the early phases of learning to read.

Adolescent↗

PubMed2004

Spatial working memory deficits in children at ages 3-4 who were low birth weight, preterm infants.

The aim of this study was to investigate attention and perceptual and spatial working memory abilities in preterm, low birth weight preschool children without evident brain disorders as determined by normal cerebral ultrasound findings and normal motor development. The authors evaluated 19 preterm and 19 typically developing children who were matched for IQ and chronological age. Results indicated that children born prematurely without major neurological deficits and with a normal cognitive level may have specific difficulty in sustained attention, visuospatial processing, and spatial working memory when evaluated at ages 3-4. This finding is relevant for understanding the qualitative aspects of cognitive development in preterm children and the neurobiological substrate underlying this development.

Attention↗

PubMed2003

Implicit learning deficit in children with developmental dyslexia.

Several neuropsychological deficits have been reported as characteristic of the cognitive profile of dyslexic children. Phonological and visual processing are often impaired as well as auditory processing, attention and information processing speed. We investigated whether implicit learning, is impaired in dyslexic children and adolescents. Tests of implicit and declarative learning were administered to 18 clinically defined dyslexics and 18 similar age controls. Dyslexics showed a reduced learning rate in the implicit but not in the declarative task, suggesting a specific deficit of implicit learning. Although alternative hypothesis cannot be ruled out, considering that implicit learning is a cognitive function primarily processed by the cerebellum and that recent neurological and physiological data suggest a cerebellar dysfunction in dyslexia, the present results suggest an impairment of cerebellar system in reading disabilities.

Analysis of Variance↗

PubMed2003

Visual and spatial working memory dissociation: evidence from Williams syndrome.

This study aimed at investigating the possible dissociation between visual and spatial working memory (WM) by means of two different experiments. In the first experiment, a WM test for visual material and for spatial information was given to a group of 202 normally developing children (chronological age 7 years 5 months, SD 1.6 years; 109 males, 93 females). Results document a different developmental trend in the two span tests. In the second experiment, we presented the same visual and spatial WM tests to a group of 13 individuals with Williams syndrome (WS), seven males and six females (chronological age mean 18 years 3 months, SD 5.1; mental age mean 7 years 2 months, SD 1.5 years), and to a control group of 26 typically developing children 14 males and 12 females matched for mental age (mean 7 years 2 months, SD 1.4). The results of this second experiment show that, on average, the spatial span obtained by individuals with WS was significantly lower than control participants, but visual span was comparable in the two groups. Our data support the hypothesis of a dissociation within the visuo-spatial sketch pad slave system in the WM model.

Amnesia↗

PubMed2003

Early linguistic abilities of Italian children with Williams syndrome.

Previous studies of linguistic and memory abilities in Italian-speaking children with Williams syndrome (WS) and Down syndrome (DS)are briefly reviewed. New data on linguistic performance of 6 Italian children with WS between 3 and 6 years of age are presented and compared with data on linguistic performance of 6 children with DS selected from a larger sample and matched for chronological age and vocabulary size and of 6 typically developing (TD) younger children matched for mental age and vocabulary size. The language measures also included a parent report of early phrase structure, a naming test, and a sentence repetition task. Analyses revealed that the 3 groups of children were at the same productive vocabulary level, but showed different patterns in sentence production and repetition. Children with WS produced more complete sentences, similar to TD children at the same vocabulary size, whereas children with DS produced more telegraphic and incomplete sentences. The difference between children with DS and those with WS was more marked on the repetition task, suggesting that phonological short-term memory may play a greater role when sentence production is measured through repetition. In addition, qualitative analysis of errors produced in the repetition test revealed interesting differences among the 3 groups. These results from younger children confirm and extend previous findings with older children and adolescents with WS. They further suggest that the apparently spared linguistic abilities of children with WS could emerge as an artifact of comparisons made to children with DS, whose sentence production competence is more compromised relative to other verbal and nonverbal abilities.

Case-Control Studies↗