Disorders which are present from one's birth have developmental trajectories which differ depending on each syndrome. It is often possible to be able to distinguish between them by paying attention to the individual differences in clinical and non-clinical samples. This essay will focus on joint attention, emotion processing and language skills in three syndromes; Prader-Willi syndrome (PWS), Angelman syndrome (AS) and Turner syndrome (TS), and will attempt to differentiate between the manifestations of the aforementioned interactive skills.
PWS is caused by an abnormality on chromosome 15 resulting is several behaviors characteristic of the syndrome such as, an insatiable appetite, intellectual disabilities, difficulty adapting to change, need for a routine, tantrums and some obsessive compulsive behavior (Ho & Dimitropoulos, 2010). AS also occurs due to the non-expression of a gene on chromosome 15. Children with AS typically have some intellectual disability, lack of speech, seizures, a short attention span, hypermotoric behavior and also seem to have a happy demeanor with easily provoked laughter (Bird, 2014). Finally, TS is caused by an incomplete X chromosome, making it a female specific disorder, and results in relatively intact intellectual function with impaired visuospatial skills and executive, social and cognitive abilities (Hong, Kent, & Kesler, 2009).
Joint, or shared attention, is when two individuals focus on one object by one person diverting the other person's gaze to said object, through pointing or eye-gazing (Moore & Dunham, 1995). Joint attention plays a major role in interaction and developing socio-emotional skills, as it allows individuals to identify intention and share information about their environment. Joint attention is often impaired in certain developmental disorders thus hindering the development of social skills. Children with PWS have been shown to have difficulties in shifting their attention from things that interest them (Dykens, Lee, & Roof, 2011), and also show comorbid symptoms of attention-deficit hyperactive disorder (Ho & Dimitropoulos, 2010). A study by Lin et al. (2003) on nonverbal communication in a sample of PWS children aged 2-7 years old and matched controls, investigated initiation and response behaviors. What they found was that the PWS group displayed more initiation of joint attention but significantly fewer responses to joint attention, than the control group. These results indicate that PWS children are not impaired in initiating joint attention but have difficulty responding to it when prompted. This could be because initiating focus on an object will involve something they are interested in, but have difficulties shifting their attention from something that captures them when needed to respond.
AS samples have been shown to have short attention spans, as well as shorter attention spans compared to Down's syndrome and PWS individuals (Tan et al. 2011). A study on an AS sample of 5-10 year olds by Summer and Impey (2011), discovered that in contrast to PWS, AS children showed a higher impairment in being able to initiate joint attention than being able to respond to it. Unfortunately, this study did not use a control sample so there is no comparison with normal development and also used a very small sample. The same results have been listed as common characteristics of AS by Legree, Condillac and Griffiths (2013), however, a larger sample study using matched controls would make these findings more reliable.
Individuals with TS also demonstrate a general inability to maintain attention throughout a task (Ross et al. 2000). Concerning joint attention, which was measured by focusing on one of its components, directional eye gaze, Elgar et al. (2002) found that eye gaze of TS individuals was comparable with controls only when gaze and head position was congruent. When TS participants could only move their gaze and not their head, their performance was worse than controls. In contrast, Lawrence et al. (2003a) found that when gaze or head position was used as a cue to be ignored in response to a target, TS and controls had similar scores with variance accounted for by performance IQ. Specifically, the TS participants were less accurate than controls when trying to ignore an incongruent gaze cue. The fact that variance was accounted for by performance IQ suggests there may be a visual-processing influence on how TS participants perform in this task.
As we see, all 3 syndromes seem to have general attentional problems and impaired joint attention behaviors which are opposite in AS and PWS. TS seems to have social cueing relatively intact.
Emotion recognition is an important aspect of social interaction as it allows an individual to monitor the reactions of the person with whom he's interacting and choose his responses accordingly. It is also something that can be impaired in certain developmental disorders. An ERP study with PWS participants of 2 genetic subtypes showed that they were more sensitive to the emotional content of nonsocial objects than faces. Furthermore, a larger late positive potential was present for faces and objects than inverted faces (Key, Jones & Dykens, 2013). This suggests that there is a larger response to arousing stimuli in general rather than emotional stimuli. There were no significant differences in responses to specific emotions in non-inverted faces, which may be due to inattention to the stimuli. Another study by Whittington and Holland (2011) also on a PWS sample of all ages found that, when presented with several pictures of the 6 basic emotions, there was 55% correct identification. Highest scores were noted when asked to recognize happiness and lowest scores for fear. Even though there is an impairment in reading facial expressions for PWS individuals which may contribute in their difficulties with interacting with peers, these studies did not use a control group so as to compare results with a typical development sample.
A prominent feature of AS is displays of happiness and apparent absence of negative emotion (Williams, 2010), which makes people easily distinguishable from other syndromes. There have been reports (Howlin, Charman & Ghaziuddin, 2011) of people with AS having difficulties recognizing their partners' emotions which are more prominent for facial expressions than hand gestures. AS are also impaired on danger recognition. Pelc, Cheron and Dan (2008) describe autistic features in AS where regulating social interactions and deciphering emotional expressions is impaired. Educational factors seem to play a significant role in interaction. Unfortunately more research is needed with control samples as well as other developmental disorders in order to fully understand how emotional recognition is impaired in AS.
There has been extensive research concerning emotion recognition in women with TS with results indicating poor categorization of affect of the 6 basic emotions (Hong, Kent & Kesler, 2009). Another study by Lawrence et al. (2003b) found that there was selective poor performance when TS individuals were asked to recognize anger and fear, compared with controls. An fMRI study showed enhanced activation of the right amygdala in TS when looking at fearful faces (Kesler, 2007). It is possible that impairment in recognition of fear stems from the impaired connectivity between the amygdala and fusiform gyrus. A study on gaze interpretation by Lawrence et al. (2003a) also found impairments on fear recognition in TS women with spared social cueing. The researchers hypothesized that amygdala dysfunction might be implicated in these results.
These studies show that there is a general impairment in recognition of facial emotions in all three disorders with recognition of fear having the least accuracy in TS and PWS.
Language is a very important component of social interaction as it directly allows individuals to communicate with one another. It is also a component which can be impaired in certain developmental disorders making it difficult to maintain a social connection in everyday interactions. Studies on PWS infants have shown that there are delays in language milestones (Dykens, Lee & Roof, 2011) with displays of vocabulary at 18 months or sometimes even 6 years, speech difficulties and problems in language, such as deficits in grammar and pragmatics (Ho & Dimitropoulos, 2010). Another deficit is poor narrative skills which may hinder individuals from communicating effectively with others. Studies have shown (Kleppe, et al., 1990, Van Borsel et al., 2007) that PWS children show greater deficits in receptive than expressive language skills. These results have been demonstrated in a study by Dimitropoulos, Ferranti and Lemler (2013) whose findings indicated that both expressive and receptive language skills were significantly lower than verbal intelligence. Furthermore, a specific genetic subtype of PWS, with maternal uniparental disomy, exhibited higher expressive than receptive language skills. This is congruent with what was mentioned above but further research is needed to determine whether different subtypes demonstrate different discrepancies relating to language.
A prominent feature of AS is the absence of language and speech modalities (Williams et al., 2006). Wilson et al. (2011) investigated the severe language delay that is present in AS using MR diffusion tensor imaging to study brain connectivity in AS children. The arcuate fasciculus is a tract connecting the language comprehension region in the temporal lobe with the speech generating region of the frontal lobe. The findings of the study revealed that the arcuate fasciculus of both hemispheres was unidentifiable in AS children compared to controls. This could account for the language impairment in AS, although it is unclear if it could also be related to the overall cognitive deficit present in this syndrome. There have been reports of receptive language being superior to expressive language in AS (Gentile, et al., 2010). This study found that non-deletion participants ' participants with a UBE3A mutation ' were less developmentally delayed than the ones with a deletion. Deletion children had weaker language skills and were generally more developmentally delayed than non-deletion children except in expressive language skills. Expressive language was more impaired than receptive language skills. A paper studying differences in genotype and phenotype in AS (Bird, 2014) replicated these results and found that patients with the UBE3A mutation scored higher on cognition, fine motor skills and receptive language compared to those with a deletion. It seems that AS is also a syndrome whose phenotype can largely vary depending on gene expression. Language, especially phonological processing seems to be a strength in women with TS (Hong, Kent & Kesler, 2009). In a study by Temple (2002), TS participants scored as well as, and even better in some cases, than controls in receptive vocabulary and reading comprehension, demonstrating intact semantic language abilities. Another study reported no language use abnormalities in TS women (Mazzocco et al., 2006). TS participants demonstrate intact language development and a study by Temple and Carney (1996) reported higher reading levels, accuracy and comprehension in TS women compared to age-matched controls. On the other hand, there has been contradicting evidence concerning these results, with language strength not appearing to be global as oral fluency skills seem to be impaired. A study by Waber (2008) compared TS patients with age and IQ-matched controls and found that TS participants scored lower than controls on word fluency, visual memory and motor learning. It seems that even though language seems to be a strength in TS, certain aspects of it can be impaired.
As can be seen from the evidence presented, PWS, AS and TS show impairments in the three areas of social interaction described. PWS children display difficulties in shifting their attention from something that interests them and also show more initiation of joint attention rather than responses to it. In contrast, AS children showed the opposite behavior with more highly impaired initiation than response to joint attention. TS girls seem to have eye gaze as social cueing rather intact compared to PWS and AS and all three syndromes have general problems with maintaining attention. Concerning emotional recognition all three syndromes seem to be impaired in correctly identifying the 6 basic emotions. PWS and TS showed selective poor performance in the recognition of fear which could stem from impaired amygdala function. More research is needed for AS individuals' ability to recognize emotions using control samples and determining whether there are differences in accuracy depending on the emotion presented. PWS children show greater deficits in receptive than expressive language skills as well as delayed development of vocabulary. The opposite results were true when it came to AS children with a greater deficit in expressive language skills. TS girls score as high as controls in semantic language tests and only display slight deficits in oral fluency skills making them superior in language abilities compared to AS and PWS. Differences of phenotype observed in these syndromes depending on individuals' genotype are present. Different gene expression resulted in discrepancies in receptive language skills scores even though participants were all diagnosed with AS.
Based on the evidence PWS and AS have opposite strengths concerning language and joint attention behaviors making them distinguishable from one another. TS differs in both these components of social interaction as patients appear to have language relatively intact as well as social cueing. All three syndromes are impaired in emotional recognition, especially fear, so it is difficult to distinguish between them based on this. However, impairment in all these domains makes the syndromes highly distinguishable from a normal development sample. Although these findings give us a clear picture of the impairments associated with these syndromes, more extensive research is needed, using larger samples, as well as control groups in order to be able to make more generalizable inferences.