Elsevier

Brain and Cognition

Volume 66, Issue 3, April 2008, Pages 290-297
Brain and Cognition

Memory abilities in Williams syndrome: Dissociation or developmental delay hypothesis?

https://doi.org/10.1016/j.bandc.2007.09.005Get rights and content

Abstract

Williams syndrome (WS) is a neurodevelopmental genetic disorder often described as being characterized by a dissociative cognitive architecture, in which profound impairments of visuo-spatial cognition contrast with relative preservation of linguistic, face recognition and auditory short-memory abilities. This asymmetric and dissociative cognition has been also proposed to characterize WS memory ability, with sparing of auditory short-term memory and impairment of spatial and long-term memory abilities. In this study, we explored the possibility of a double memory dissociation in WS (short- versus long-term memory; verbal versus visual memory). Thus, verbal memory abilities were assessed using California Verbal Learning Test and Digit Span and Rey-Osterrieth Complex Figure and Corsi Blocks was used to assess visual–spatial memory abilities. Overall, WS subjects were found to present a generalized significant impairment in verbal and visuo-spatial components either in short- or long-term memory. In sum, data from this study brings support for a developmental delay hypothesis, rather than a double dissociation within memory systems in WS.

Introduction

Williams syndrome (WS) is a neurodevelopmental disorder, with a prevalence of 1 in 7500 (Stromme, Bjornstad, & Ramstad, 2002), characterized by a deletion on chromosome 7 q11.22-23 (Korenberg et al., 2000). Of further note, WS patients have an unusual phenotype, which includes a distinctive profile of physical, medical, neurocognitive and neuroanatomical characteristics. Physical characteristics include craniofacial and cardiac/pulmonary abnormalities, growth delay, hypercalcemia, hyperacusis and feeding difficulties (Metcalfe, 1999). The other main component of the WS phenotype is a neurodevelopment/cognitive profile characterized by mental retardation and an asymmetrical development, with weak and strong areas of performance. Specifically, severe impairment of visuo-spatial cognition has been described as coexisting with a relative preservation of face recognition, auditory short-term memory, language and narrative skills (Bellugi et al., 2000, Gonçalves et al., 2004, Gonçalves et al., 2005, Mervis et al., 2000).

This uneven cognitive profile of relative strengths and weaknesses also seems to be evident within each cognitive domain. For example, several studies found evidence for the existence of a good short-term verbal memory, even when compared with normal development controls (Bellugi et al., 1994, Mervis et al., 1999, Nichols et al., 2004). However, several authors have been finding that this short-term verbal memory strength is not generalized across different memory systems (Vicari et al., 2003, Vicari et al., 1996). For example, differences of ability in short- and long-term memory storage systems were found in a study by Vicari et al. (1996). The authors compared memory performance on Digit Span, Corsi Blocks, Rey-Osterrieth Complex Figure and a word list task in a WS group and a verbal mental age matched group. While a spatial span (Corsi Blocks) was found to be significantly reduced in the WS group, no significant differences were found in terms of verbal span. Additionally, no primacy effect in the serial position curve was found with the WS group. The authors interpreted their results as an evidence for the impairment of semantic long-term memory along with the preservation of short-term phonological memory. This claim was further supported by Nichols et al. (2004) using California Verbal Learning Test (CVLT).

More recently, Brock, Brown, and Boucher (2006) replicated the Vicari et al. (1996) study, introducing some procedural changes. Namely, the serial position curve was obtained in three different presentation conditions: different words, repeated words in different order and a repeated list. Using this strategy, both groups (WS and control) showed a similar pattern of recency, but no primacy effects in serial position curve. Additionally, participants were trained with a cumulative rehearsal strategy in order to determine the primacy effect extension. Again, no significant differences were found between groups in global performance (i.e., the rehearsal strategy was not associated with a better performance), but now, a primacy effect was observable in both groups. The authors suggested that there is not a selective long-term memory deficit in WS and that the absence of a primacy effect in WS may related with the inability in using rehearsal strategies.

A dissociation in working memory components (between phonological loop and visuo-spatial sketchpad) has been also proposed for characterizing cognitive profile of WS (Jarrold, Baddeley, & Hewes, 1999). These authors tested the hypothesis of the preservation of phonological loop coexisting with impaired visuo-spatial sketchpad in WS. Twenty-five children with Down syndrome (DS) were compared with 16 children and young adults with WS and 17 children with moderate learning disabilities, in short-term verbal memory (Digit Span) and short-term visuo-spatial memory (Corsi Blocks). The results revealed that WS had the lowest score in short-term visuo-spatial memory contrasting with a superior Digit Span performance. In a second study, the authors matched three groups in terms of nonverbal mental age (WS, learning disabilities and a normal development), comparing their performance in three short-term memory measures: one verbal (Digit Span) and two nonverbal (Corsi Span and Pattern Memory). Again, the results showed that WS group had significant lower scores in Corsi Blocks. However, in the Pattern Memory test, WS group was not impaired with respect to the control group. The authors concluded suggesting the existence of a specific impairment in visuo-spatial sketchpad and a relative sparing of the phonological loop in WS. However, more recently, Jarrold, Baddeley, and Phillips (2007) proposed that these visuo-spatial memory deficits may be secondary to visuo-spatial processing difficulties, a main feature of WS cognitive profile (Mervis et al., 2000). Indeed, WS patients exhibit difficulties in several aspects of visual–spatial cognition, including spatial representations (Farran and Jarrold, 2005, Hoffman et al., 2003), abilities that are necessary to perform some visual–spatial memory tasks. The preservation of WS performance in Pattern Memory Test was interpreted by Vicari and colleagues (2003) as suggesting that WS represents a natural case of dissociation within the two components of visuo-spatial sketchpad, in which visual perception is relatively preserved. These results were further investigated with respect to long-term memory system, showing that individuals with WS had impairments in learning visual–spatial material, although a typical performance in visual-object long-term memory (Vicari, Bellucci, & Carlesimo, 2005).

Overall, previous studies have been showing evidence for an uneven performance in WS individuals across different memory tests. The current study attempts to confirm the existence in WS of a double dissociation in memory systems between short- versus long-term memory as well as between verbal and visuo-spatial working memory components.

Section snippets

Participants

A group of 14 individuals with WS (7 male and 7 female participants), with age range between 8 and 29 years (M = 16.79, SD = 5.68; mean Full Scale IQ = 49.14, SD = 7.50, range 40–61) was compared with a normal development group (N = 14, 5 male and 9 female) ranging in age from 8 to 29 years (M = 17.93, SD = 6.10; mean Full Scale IQ = 110.50, SD = 10.48, range 90–124). Given that the neurological profile of WS may change across development (Gagliardi, Martelli, Burt, & Borgatti, 2007), two subgroups were compared

Results

The results are presented for each test. First, we present the scores obtained in CVLT, Digit Span and Corsi Blocks in the two comparison groups. Finally, Rey-Osterrieth Complex Figure results are reported.

Discussion

Overall, the results of this study demonstrate that WS individuals have a global impairment of working memory components (phonological loop and visuo-spatial sketchpad). In addition, we failed to observe significant differences in short- versus long-term memory storage systems, as they were equally affected in WS subjects.

The differences between our study and some studies, who found evidence for the dissociation hypothesis in WS memory, may be due to different criteria in selecting the control

Acknowledgments

This research was supported by the Grants POCTI/PSI/58364/2004 and SFRH/BD/16091/2004 from Fundação para a Ciência e Tecnologia (Portugal).

References (34)

  • S. Nichols et al.

    Mechanisms of verbal memory impairment in four neurodevelopmental disorders

    Brain and Language

    (2004)
  • T. Verguts et al.

    On the correlation between working memory capacity and performance on intelligence tests

    Learning and Individual Differences

    (2002)
  • S. Vicari et al.

    Memory abilities in children with Williams syndrome

    Cortex

    (1996)
  • U. Bellugi et al.

    I. The neurocognitive profile of Williams syndrome: A complex pattern of strengths and weaknesses

    Journal of Cognitive Neuroscience

    (2000)
  • U. Bellugi et al.

    Williams syndrome: An unusual neuropsychological profile

  • J.H. Bernstein et al.

    Developmental scoring system for the Rey-Osterreith Complex Figure: Professional manual

    (1996)
  • Corsi, P. M. (1972). Human memory and the medial temporal region of the brain. Unpublished doctoral thesis, McGill...
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