AUTISM : CURRENT ISSUES 22
While these notes are a summary of only three recently published studies, they are significant in highlighting some clear-cut findings.
Reference is made to further evidence for the lack of efficacy in using secretin to treat the core symptoms of autism; and there is specific information concerning the nature of attentional deficits among children with autism with implications for teaching style and curriculum organisation
M.J.Connor March 2002
The work of Goldstein et al (2001) begins with a review of research into attentional style in autism and the authors note how dysfunctions in attention have been regarded as a core area of deficit among individuals with autism in the light of atypical responses to environmental stimuli or of weaknesses in information processing within which attention appears to be critically implicated.
Recent theories have linked the apparent deficits in attention to weaknesses in executive functioning. However, studies show limited consistency in defining the precise nature of the deficits or in describing attentional abilities which are intact. This is attributed at least partly to a lack of agreement concerning now to define attention itself.
Over the years the particular attentional characteristics of individuals with autism have been attributed to deficits in the arousal, orientation, filtering, and gazing components of attention; with one early model explaining repetitive or stereotypical behaviours and limited social development in terms of some underlying deficit in the modulation of arousal. Further, both under- and over- arousal have been perceived to underlie characteristic deficits in autism, although both views are no longer current.
Another frequently cited theory concerns over-selectivity as an explanation of the observed ability to focus upon detail while failing to interpret multiple cues in the environment. One school of thought has argued that this apparent over-selectivity is secondary to a form of tunnel vision or over selective gaze although further observations have indicated that this characteristic is related to developmental level and is not observed among higher functioning and older individuals with autism.
Accordingly there has been explored the possibility that problems with attention result from an inability to filter out irrelevant stimuli.
A recent theory has explored the issue of deficits in reflexive visual orienting although further studies have produced inconsistent findings indicative of no overall visual orienting deficit but of problems with disengagement and shifting attention according to the level of processing demands within the task.
In any event, the authors summarise this whole area by concluding that there are no existing and consistent data to support arousal deficits, over-focusing, over-selective gaze, inadequate filtering, or orienting deficits as key explanations of the attentional style or deficits characteristic of individuals with autism.
It is then noted that the often-observed perseverative behaviour gives some support to the theory of deficits in sustained attention or vigilance, although there is evidence for adequate or even enhanced ability for sustaining attention among individuals with autism, at least when the focus of attention is self chosen.
Further, the various studies exploring attention deficit disorder which have included samples of individuals with autism have suggested no consistent deficits in visual sustained attention in this latter group although there is limited evidence that autistic individuals perform poorly on auditory continuous performance tasks when compared to controls.
Is then a core deficit to be located within the area of shifting attention, a deficit related to parietal lobe dysfunction, with Courchesne et al (1994), for example, hypothesising that individuals with autism cannot readily shift from one stimulus to another, or shift between sensory modalities, or disengage attention?
The current study by Goldstein et al (opp.cit) set out to explore further aspects of attention highlighted in several hypotheses about attention in autism.
In order to be clear about their terms, they adopted the 4-factor model of attention proposed by Mirsky et al (1991) which subdivides attention into the ability to
Focus on a target object and complete a task in the presence of distracting objects
Maintain vigilance over a sustained time period
Shift the focus of attention
Receive and interpret incoming information.
The participants were 103 high-functioning individuals with autism, covering a range of ages with a mean of 18 and whose IQs all fell well above 70; and a control sample.
The assessment battery included measures of encoding (using digit span and arithmetic from the Wechsler Scales) ; focusing (as measured in a task involving marking a target letter from a long array of letters, and in the Stroop Test where participants read a list of colour names or name the colour of printed words when the word and the print colour conflict); sustained attention (using a continuous performance test such as having to press a computer space bar every time a given letter appears on a screen); shifting attention (a card sorting task involving different categories for sorting); and motor skill (finger tapping and pegboard tasks).
The hypothesis was that the autistic sample would perform poorly on measures of attention only when the task involved a higher level executive function or a psychomotor component; and results demonstrated that, in this sample of high-functioning individuals with autism compared to controls, the major weaknesses did indeed apply to those attentional tasks requiring cognitive flexibility or psychomotor speed as opposed simply to accuracy or span of attention.
In other words, differences were noted on the focus and shift elements and not on the vigilance and encode factors of the attention model, so that there is no support for the view that individuals with autism have difficulties with encoding information or sustaining attention over time. Meanwhile, the findings were found not to be confounded by developmental features the younger and older participants showed the same differences (or lack of them) when compared with controls.
These findings are consistent with various previous studies, such as that of Pascualvaca et al (1998), indicating that even quite demanding attentional tasks without the conceptual or psychomotor component do not differentiate high functioning autistic individuals from controls. There is also confirmation, therefore, that there is no invariable problem in autism with regard to making simple perceptual shifts but there is a consistent difficulty when the shift is at a conceptual level.... in, for example, switching from a task of sorting a set of objects by shape to a task of sorting the objects by colour.
In summary, the authors held that the cognitive deficits and characteristic behaviours associated with autism are not the result of a failure to incorporate information or to sustain concentration or to resist distraction. The attentional defects, where they are observed, are at the conceptual level, with implications for executive functions and the monitoring of novel information, and for the ability to organize information along with monitoring ongoing events and making rapid adjustments.
Relevant to the issue of attention is a recent report describing structural anomalies in the brains of individuals diagnosed with autism.
Casanova et al (2002) found that autistic people differed from normally developing people in the size, number, and arrangement of minicolumns which are the basic functional units of the brain. This finding emerged from computerised imaging to analyse brain regions, notably the prefrontal cortex and the temporal lobe.
In the autistic sample, the minicolumns were more numerous, smaller, and less compact in their arrangement than those found among the control sample. The authors held that the finding of a greater number of minicolumns supported the theory that people with autism are actually flooded with stimuli rather than being starved of stimuli. The implication is that certain autistic behaviours may represent a kind of defence against the volume of input; but it is further argued that, under certain circumstances (such as when the individual is allowed to focus upon activities of his/her own choice ??), this brain structuring could bring about some benefits in allowing the individual to focus better upon the task in hand.
(One might argue that this finding is important in providing further information concerning how the various factors interacting in the etiology of autism, notably genetic influence, lead to structural as well as psychological and behavioural characteristics; and it further demonstrates the physical reality of autism, finally to end all speculation linking autism with purely psychogenic factors such as "emotional refrigeration").
The Perceived Ineffectiveness of Secretin in Treating ASD
The most recent Brown University Child and Adolescent Psychopharmacology Update (4 2002) offers a summary and commentary relating to a new controlled study which has found further evidence that secretin (either synthetic or extracted from pigs) is no more effective than a placebo in dealing with autistic symptoms and behaviour.
Secretin promotes the release of digestive fluids from the pancreas, bile from the liver, and pepsin from the stomach; and interest in its possible efficacy in dealing with the core symptoms of autism arose from a small number of anecdotal reports and initial trials which suggested that this hormone, commonly used in diagnostic gastrointestinal tests, was effective in improving the social and language skills in children with autism. (See, for example, Horvath et al 1998.)
The urgency in implementing this controlled study (Owley et al 2001) was linked to the observation that secretin was being prescribed increasingly frequently for individuals with autism when there was no real and systematic evidence for its safety or for its value. In fact, it is argued that the intravenous use of secretin may have side effects such as allergic reactions.
Owley argued that clinical practice must be based as far as practicable upon sound empirical investigations involving double-blind and placebo-controlled testing, and their own study did involve such a structure where the target sample was a group of 56 children between the ages of 3 and 12 with diagnoses of autism according to DSM-III criteria.
The effects of porcine secretin was examined over an eight week period during which the subjects were randomized to an intravenous dose of saline followed at week 4 by a dose of secretin, or vice versa.
A battery of baseline measures were used, including the Autism Diagnostic Observation Schedule, the Autism Diagnostic Interview, and the Developmental Test of Visual Perception; and these were re-used after week 4 and week 8. The parents completed the Vineland Adaptive Behaviour Scales before the study began; and used various checklists, including the Gilliam Autism Rating Scale and the Aberrant Adaptive Behaviour Scales, at the end of weeks 2, 4, 6, and 8.
Analysis of results revealed no significant differences between the placebo-treated and secretin-treated groups.
Over the course of the study, some measures showed improvement, but this improvement took place independently of whether secretin or placebo was used and of the order in which either treatment was used.
The authors acknowledge some limitations in their study such as the fact that only one dose of secretin was used (although the Horvath study reported an initial response to secretin at a dosage similar to that used in the present study). Further, there was no analysis of differences in response relative to age, severity of deficits, and gastrointestinal status. Nevertheless, it was concluded that, much as one would have liked to identify some simple treatment that can relieve some of the core symptoms of autism, the results of this study replicate the negative findings of other controlled clinical trials in respect of the use of secretin.
The authors argue that, with this current finding, it can be underlined that there is no evidence for positive outcomes from secretin, so that continuing use of this treatment would be a matter of exposing the child to risk without known benefit.
M.J.Connor March 2002
Casanova M. et al 2002 Structural brain abnormalities identified in autistic patients.
Summary report in Medscape: February 2002. Original article in Neurology 58 428-432
Courchesne E., Townsend J., Akshoomoff N., et al 1994 Impairments in shifting attention in autistic and cerebellar patients. Behavioural Neuroscience 108 848-865
Goldstein G., Johnson C., and Minshew N. 2001 Attentional processes in autism. Journal of Autism and Developmental Disorders 31(4) 433-446
Horvath K., Stefanatos &, Sokoiski K., et al 1998 Improved social and language skills after secretin administration in patients with autistic spectrum disorders. J. Assoc.. Acad. Minor Phys. 9 9-15
Mirsky A., Anthony B., Duncan C., Aheani M., and Kellam 5. 1991 Analysis of the elements of attention Neuropsychology Review 2 109-145
Owley T., McMahon W., Cook E., et al 2001 Multisite, double blind, placebo controlled trial of porcine secretin in autism. Journal of the American Academy of Child and Adolescent Psychiatry 40(11)1293-1299
Pascualvaca D., Fantie B., Papageorgiou M., and Mirsky A. 1998 Attentional capacities in children with autism. Journal of Autism and Developmental Disabilities 28 467-478
© Mike Connor 2002.
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