Recent Research on Autistic Spectrum Disorder

Causes & Associated Features

Introduction

Causes of ASD have increasingly been attributed to genetic, or prenatal factors. These have affected underlying neuro-anatomical parts of the brain. Substances ingested through the diet have also been blamed for ASD. This has led to problems with language, memory, ability to learn, as well as social development and motor co-ordination as well as rigidity of behaviour.

 Causes and Associated Features

There is considerable evidence that genetics as well as the environment play a role in the development of autistic spectrum disorder (ASD) type individuals. Genetic factors frequently influence underlying neuro anatomical parts of the brain leading to autistic behaviour (Toal, Murphy, & Murphy, 2005; Swanson, Fossella, Grady Moyzis et al., 2006). These neural problems also affect the executive functioning of such young people (Schmitz, Rubia, Daly, Smith, et al., 2006). It should however, be made clear that at this point there is no single aetiology or given cause to explain ASD. It is possible that some substances or compounds, once eliminated from the diet, or pharmaceutically washed out, could reverse or ameliorate some of the co-morbid symptoms in ASD. So far however, there is no scientific evidence that any compound could influence in any respect the course of the treatment, or could be responsible for any abnormality in ASD (Pavone, & Ruggieri, 2005).

Many children who suffer from ASD have impaired motor control and often have impaired motor detection (Milne, White, Campbell, Swettenham, et al. 2006). There is however, evidence for functional abnormalities and metabolic disconnectivity in social brain circuitry. McAlonan, Cheung, Cheung, Suckling et al. (2005) noted that children with autism had a significant reduction in total grey matter. Taken together their data suggests abnormalities in the anatomy and connectivity of limbic striatal social brain systems which may contribute to the brain metabolic differences and behavioral phenotype in autism.

The human secretin gene could well be responsible for this in children with autistic spectrum disorders. Ng, Chow, & Wong, (2005) however did not find evidence of a relationship between human secreting gene mutation and autism.

ASDs are relatively common among neuro-developmental conditions and confer lifelong disabilities. As the majority of affected children will have sensory modulation difficulties, this has significant implications for paediatric occupational therapy services (Adamson, OHare, & Graham, 2006).

Another investigator (Akshoomoff, 2005) found specific aspects of memory processing and language development lacking in ASD. An association between autistic spectrum disorder and imitative impairment might also result from a dysfunction in mirror neurons (MNs). It was also found that activity in the right parietal lobe was less extensive in the ASD group and was absent during non imitative action execution. Brocas area was minimally active during imitation in controls. Hence Williams, Waiter, Gilchrist, Perrett et al. (2006) suggest that ASD is associated with altered patterns of brain activity during imitation, which could stem from poor integration serving visual, motor, proprioceptive and emotional functions.

ASD must be viewed according to Akshoomoff (2005) as a condition related to behaviour, neuropsychological development and early identifiable with pre-schoolers or even before.

Efforts have been made to develop a number of rating forms or checklists including the Social and Communication Disorder Checklist (SCDC). The object is to fulfil the need for a sensitive measure of autistic traits. Traits measured by the SCDC were noted to be highly heritable in both genders (0.74). According to Skuse, Mandy & Scourfield (2005) the SDCD is a unique and efficient first level screening questionnaire for autistic traits. Another rating form frequently used is the Gilliam Autism Rating Scale used by the researchers Adamson et al. (2006) previously mentioned.

It has already been stated that some children with ASD have a reduced ability to detect visual motion. Hence their problems with motor co-ordination (Milne, Swettenham, & Campbell (2005). There are other symptoms typical of ASD. These include rigidity of behaviour, especially in social interactions (Trepagnier, Sebrechts, Finkelmeyer, Stewart et al., 2006), problems with memory and attention (Lloyd, Paintin, & Botting, 2006), and visual as well as auditory impairment (Gibbons, 2005). Some researchers consider that there appears to be an association in some cases between ASD and epilepsy. However, epilepsy is not considered to be the cause of autistic behaviour (Deonna, & Roulet, 2006; Clarke, Roberts, Daraksan, Dupuis et al., 2005). There are also behavioural difficulties and daytime sleepiness identified in such children which affect their ability to learn.

Needless to say when autistic spectrum disorders are associated with visual impairment there are considerable difficulties with learning and in other areas of effective functioning (Dale, 2005; Fletcher-Watson, Leekam, Turner and Moxon, 2006). This is a double handicap. The same can be said when an autistic spectrum disordered child also suffers from deafness or partial deafness (Garcia & Turk, 2007). There are however, also signs of precocious reading ability in some children with the ASD disorder who may suffer at the same time from the absence of spontaneous speech ( Atkin, & Lorch, 2006).

Summary

Evidence shows that there is a genetic aspect as well as environmental aspect to ASD. The neural problems associated with this affect the executive functions of such young people. There is however, no single aetiology or cause to explain ASD. Many children with ASD suffer from problems with language, memory and ability to learn as well as social development and motor co-ordination. They also show a rigidity in behaviour.

 

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