Biology 202, Spring 2005
Third Web Papers
On Serendip

You are at the park, and a child comes running up to you. You have never met her before, but she displays a familiar friendliness as if she's known you all her life. She's only three years old, but she has an amazing way with words that adds to her remarkable sociability skills and engaging personality. It's not obvious at first, but when you take a closer look at her, you notice distinctive physical traits. When you look into her eyes, she has a star-shaped iris with full periorbital surroundings. Aside from her eyes, she has a full nasal tip and flattened nasal bridge, a wide mouth with full lips and cheeks, a long indentation in the midline of her upper lip, and a small jaw. This child has Williams Syndrome.

People with Williams Syndrome (WMS) function in the mild range of mental retardation, and they possess IQs averaging about 60.1) Williams Syndrome They have a distinctive neuropsychological profile that includes strengths in face perception, affective attunement, short-term auditory memory and select aspects of language, countered with weaknesses in visuospatial, motor, visuomotor integration, and arithmetic skills.1) Williams Syndrome It is hypothesized that the diverse brain regions and its variations account for different functions within larger networks provide the physiological bases for the specific strengths and weaknesses found in Williams Syndrome. Although the overall cognitive abilities of individuals with WMS are typically in the mild-to-moderate range of mental retardation, the peaks and valleys within different cognitive domains make this syndrome especially fascinating to study. Their display of strengths and weaknesses of uneven cognitive profile and atypical parts of specific areas of the brain is one of the reasons that make the study of Williams Syndrome so interesting for me.

Williams Syndrome is caused by a small genetic deletion on the long arm of chromosome 7, encompassing approximately 25 genes.2)Williams Syndrome This deletion codes for four genes that are highly expressed in the brain, FZD9, STXIA, LIMK1, and CYLN2. In addition, the whole brain volume is about fifteen percent smaller than normal, but the superior temporal gyrus, an area that encompasses primary auditory cortex, is of approximately normal volume.1) Williams Syndrome Preliminary structural MRI evidence suggests an exaggerated leftward asymmetry of the planum temporal gyrus.1) Williams Syndrome

As mentioned briefly before, people with Williams Syndrome possess a heightened interest in music and preserved language abilities. The language of individuals with Williams Syndrome sometimes seems precocious in their use of unusual words and conversational flourishes.3)Williams Syndrome These strengths may be due to their neurological traits of the brain structure. Although it is smaller as a whole, a small study using auditory event-related potential found increased amplitude of early endogenous components suggesting hyperexcitability of the primary auditory cortex.1) Williams Syndrome And it might be their alterations of the function in this area of the brain that may explain the rate of hyperacusis and language/music perceptual processes. Also, the planum temporale has been linked to hemispheric dominance for language. In musicians with perfect pitch, there appears to be even more pronounced leftward asymmetry of this region, like that of a person with Williams Syndrome.1) Williams Syndrome

The distinctive cognitive profile of individuals with WMS includes relative strengths in language and facial processing and profound impairment in spatial cognition. Studies have shown that subjects with WMS fail to attain the level of conceptual restructuring that most normal children achieve by age 10 or 11 which suggests that they possess a limited biological knowledge and understanding. 4) Bellugi, U., Lichtenberger,L., Jones, W. Lai, Z. (2000). The Neurocognitive Profile of Williams Syndrome: A Complex Pattern of Strengths and Weaknesses.Journal of Cognitive Neuroscience, pp. 7-29. San Diego: Massachusetts Institute of Technology. Despite this handicap, they have relatively spares expressive language. Their use of noticeably complex language shows that language is a major strength in the WMS cognitive profile. In the different stages of language development, the behavioral phenotype of WMS undergoes dramatic change across the first years of life, starting out with extreme delay at all developmental milestones, including language.4) Bellugi, U., Lichtenberger,L., Jones, W. Lai, Z. (2000). The Neurocognitive Profile of Williams Syndrome: A Complex Pattern of Strengths and Weaknesses.Journal of Cognitive Neuroscience, pp. 7-29. San Diego: Massachusetts Institute of Technology. They are extremely behind at the initial stages compared to normally developing children, but they begin to display a strong advantage for grammar later in development. WMS children are able to say many words they do not understand.
As grammar emerges, children with WMS in general improve dramatically, and they show relative strength in their facility and ease in using sentences with complex syntax, not generally characteristic of other mentally retarded groups.4) Bellugi, U., Lichtenberger,L., Jones, W. Lai, Z. (2000). The Neurocognitive Profile of Williams Syndrome: A Complex Pattern of Strengths and Weaknesses.Journal of Cognitive Neuroscience, pp. 7-29. San Diego: Massachusetts Institute of Technology. Given their level of other cognitive abilities, WMS individuals use sophisticated language, particularly in vocabulary. Sometimes these words are used correctly, but other times they are partially, but not completely, appropriate in the accompanying context. They sometimes use words often in the right semantic field, but fail to convey the semantic nuances appropriately. They show more of an inclination to use unusual words, which was shown through an experiment in which subjects were asked to name all the animals they could in a minute. WMS subjects not only gave significantly more responses than mental-age matched normal control, but they also gave many more uncommon animal names.4) Bellugi, U., Lichtenberger,L., Jones, W. Lai, Z. (2000). The Neurocognitive Profile of Williams Syndrome: A Complex Pattern of Strengths and Weaknesses.Journal of Cognitive Neuroscience, pp. 7-29. San Diego: Massachusetts Institute of Technology. Although WMS individuals are able to produce a variety of grammatically complex forms with sophisticated vocabulary, they make occasional morphosyntactic and systematic errors especially if the language is about spatial relations.

Despite these strengths, they also have profound visuospatial weaknesses. They have difficulties visualizing the spatial relationships between objects, their distances and overall configuration. They have particular weaknesses in dealing with numerical concepts, spatial cognition and in abstract reasoning.3)Williams Syndrome In the mid-1990's, these deficits of visuospatial abilities was linked to the deletion of L1MK1, one of the four brain-expressed genes. However, further studies have shown that deletions involving this gene still displayed an intact spatial ability.1) Williams Syndrome This goes to show that there may not be one easy answer to explain a certain deficit or even a strength. It might just be specific combinations.

When WMS subjects were asked to draw an illustration, the product typically had poor cohesion and overall organization within the images. WMS subjects' spatial deficits tend to plateau and remain basically at the level of normally developing 5-year-olds.(4) Drawings of car by WMS individuals may show a door, a tire and headlights, but the parts might be depicted in an unrecognizable relationship to each other. It seems as though WMS subjects typically produce primarily the local forms, and they are impaired at producing the global forms.4) Bellugi, U., Lichtenberger,L., Jones, W. Lai, Z. (2000). The Neurocognitive Profile of Williams Syndrome: A Complex Pattern of Strengths and Weaknesses.Journal of Cognitive Neuroscience, pp. 7-29. San Diego: Massachusetts Institute of Technology. This suggests that people with WMS have a bias toward fractionation and an over attention to detail at the expense of the whole.

The functional segregation of visual processes in the brain is split by visual domain into a dorsal stream that connects the occipital cortices and the parietal lobe and a ventral stream of information flow from the occipital to the temporal cortices.1) Williams Syndrome Although this disorder causes spatial deficits, it seems to play a positive role in face perception and recognition. The fusiform gyrus, a region on the underside of the temporal lobes, seems to have a specific role in face perception. Specifically, the presence of the anatomical connection between the fusiform gyrus and limbic areas of the brain may be responsible for many emotional processes that function for face perception.1) Williams Syndrome Subjects with WMS demonstrate a remarkable ability to recognize, discriminate, and remember unfamiliar and familiar faces. While there are gross deficits in general cognitive abilities, subjects with WMS typically exhibit a distinctive pattern of peaks and valleys in visuospatial cognition: An emphasis on local over global processing and extreme fractionation in drawing; yet an island of sparing for processing, recognizing, and remembering faces.4) Bellugi, U., Lichtenberger,L., Jones, W. Lai, Z. (2000). The Neurocognitive Profile of Williams Syndrome: A Complex Pattern of Strengths and Weaknesses.Journal of Cognitive Neuroscience, pp. 7-29. San Diego: Massachusetts Institute of Technology.

There may also be a connection with high face perception and social-cognitive skills. It is believed that being able to have keen face perception and understanding the emotional states of others through facial cues may be closely tied to social-cognitive skills and the ability to form and maintain social relationships.1) Williams Syndrome This hypothesis is supported by a study with autistic people, who display a lack of interest in social relationships, seem to fail to engage the fusiform gyrus during face perception tasks.1) Williams Syndrome While there is no activation of this region for autistic people, individuals with Williams Syndrome seem to have normal use of the fusiform gyrus for face perception. In other words, levels of fusiform gyrus activation can be related to levels of social relatedness. If this is true, in normal brains, can we account for personality differences in sociability to the way our brains, specifically the fusiform gyrus, reacts? And can we say generalize this hypothesis to say that people who are keen at face perception and recognition have higher sociability skills?

This concept of connecting the fusiform gyrus to social relatedness may not work for normal brains and personality traits. In terms of brain studies, it was found that face recognition in healthy adults was associated with scalp voltage waveforms are predominantly localized to the right hemisphere. In contrast, ERP's in adolescents and adults with Williams Syndrome were found to be distributed across both hemispheres and did not distinguish between human faces, monkey faces, and cars.3)Williams Syndrome In normal brains, the cortical specialization for face processing observed in normal adults is achieved through gradual experience-driven specialization of an initially more general-purpose visuo-spatial processing system. However, in Williams Syndrome patients, genetic effects during brain development generate initial cortical structures with different neurocomputational biases which yield an overall processing that is poorer but have circuits with greater potential to process isolated features than configurations.3)Williams Syndrome
Individuals with WMS were significantly slower in development early in their lives, but then improved in language with increasing age. In contrast, in the visuo-spatial domain, subjects with WMS showed extreme deficit and limited change in ability across the age-range studied.4) Bellugi, U., Lichtenberger,L., Jones, W. Lai, Z. (2000). The Neurocognitive Profile of Williams Syndrome: A Complex Pattern of Strengths and Weaknesses.Journal of Cognitive Neuroscience, pp. 7-29. San Diego: Massachusetts Institute of Technology. Although they performed at a higher level in face recognition, other areas of spatial understandings were extremely lacking. Then we can ask whether or not there exists a relation between language and other aspects of cognition. Can language separate from other general cognitive abilities? Does Williams Syndrome represent the dissociation between language and general cognitive function?

By continuing the study of individuals with WMS, we are able to find out the separability of cognitive domains that normally develop together. Hopefully, others can learn that although some people with handicaps may score low on IQ tests, it does not completely dismiss their whole being as impaired. There are valleys and peaks within the test that show, although they might lack in certain areas, they might also be able to surpass a normal-developed person and possess relative strength in other areas. There have been numerous tests to better understand the ways in which individuals with Williams Syndrome display certain weaknesses and strengths, especially in recognizing faces. There seems to be increasing evidence, however, that the ways in which people with this disorder process incoming stimuli may be atypical compared to that of a healthy adult. Then does that mean that it is possible to be good at certain tasks when using abnormal processing mechanisms? This first peek through the window of the mind and brain progression of an individual with Williams Syndrome has revealed that nothing is simple or direct.

References
(1) http://info.med.yale.edu/chldstdy/plomdevelop/genetics/01aprgen.htm
(2) http://spnl.stanford.edu/disorders/williams.htm
(3) http://www.psyc.bbk.ac.uk/people/academic/thomas_m/cortex_semel_rosner_cortex_
review.pdf
(4) Bellugi, U., Lichtenberger,L., Jones, W. Lai, Z. (2000). The Neurocognitive Profile of
Williams Syndrome: A Complex Pattern of Strengths and Weaknesses.Journal of Cognitive Neuroscience, pp. 7-29. San Diego: Massachusetts Institute of Technology.


| Course Home | Serendip Home |