Difference between revisions of "Weak Coherence"

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Participants with autism appear to be able to integrate the various properties of an object and to process the meaning of individual words, but it is when people with ASD have to integrate words or objects as a whole that coherence is weak. Additionally, participants may seem to display global processing when really the result is a chaining effect, where a global view can be created by taking into account only items that can be processed locally.   
 
Participants with autism appear to be able to integrate the various properties of an object and to process the meaning of individual words, but it is when people with ASD have to integrate words or objects as a whole that coherence is weak. Additionally, participants may seem to display global processing when really the result is a chaining effect, where a global view can be created by taking into account only items that can be processed locally.   
  
====Neuropathophysiology===
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===Neuropathophysiology===
 
One explanation is that weak coherence is a result of reduced connectivity throughout the brain caused by a lack of synchronization of activities in the brain, lack of connecting fibers, and faulty top down regulation. A second explanation is that there are specific pathways that are abnormal in people with ASD, specifically the right hemisphere., because individuals with right hemisphere damage show deficits in integrating information for global meaning. <sup>10</sup>
 
One explanation is that weak coherence is a result of reduced connectivity throughout the brain caused by a lack of synchronization of activities in the brain, lack of connecting fibers, and faulty top down regulation. A second explanation is that there are specific pathways that are abnormal in people with ASD, specifically the right hemisphere., because individuals with right hemisphere damage show deficits in integrating information for global meaning. <sup>10</sup>
 
* Evidence
 
* Evidence

Revision as of 17:21, 2 February 2010

Weak Coherence and ASD

Description

  • History

The Weak Central Coherence theory for ASD was first suggested by Uta Frith to explain the results for autistic participants' performance on theory of mind tasks. As the theory became more well-known, scientists saw that, in contrast to theory of mind false-belief tasks where approximately 20 percent of autistic study participants passed, all autistic participants showed significant task performance differences compared with control groups on tasks designed to test for central coherence. So the theory began to evolve beyond Frith's original proposition as scientists began to suggest that central coherence characterizes autistic people at all levels of theory of mind ability. Some scientists believe that this theory is a more useful framework than the Theory of Mind for explaining the cognitive causes of ASD because it also explains the superior performance of ASD study participants on certain detail oriented tasks as well as the weaker performance on other theory of mind tasks. Another useful way to think of autism is by accepting both Theory of Mind and Weak Coherence as working together to explain ASD in entirety.2

  • Theory

Central Coherence refers to a person's ability to understand things in a specific context. The Theory of Weak Coherence as it applies to ASD suggests that people with ASD preferentially use a detail-focused processing style over a more global, integrative processing style that predominates as a person ages. This bias toward detail-focused processing can be seen through open-ended tasks which require strong attention to detail, where the ASD research group participants perform significantly better than the typically developing control group. ASD patients, however, still are able to globally process stimuli as seen in selective attention tasks where participants are explicitly told to pay attention to global information. In particular, one popular way of examining processing style bias in ASD is through facial processing because faces could be processed both featurally or configurally. However,these findings cannot necessarily be generalized to other types of stimuli because of the special significance of faces in processing. 1

Participants with autism appear to be able to integrate the various properties of an object and to process the meaning of individual words, but it is when people with ASD have to integrate words or objects as a whole that coherence is weak. Additionally, participants may seem to display global processing when really the result is a chaining effect, where a global view can be created by taking into account only items that can be processed locally.

Neuropathophysiology

One explanation is that weak coherence is a result of reduced connectivity throughout the brain caused by a lack of synchronization of activities in the brain, lack of connecting fibers, and faulty top down regulation. A second explanation is that there are specific pathways that are abnormal in people with ASD, specifically the right hemisphere., because individuals with right hemisphere damage show deficits in integrating information for global meaning. 10

  • Evidence

Extensive research has suggested that those with ASD have exceptional local processing abilities, possibly at the expense of global and configural processing, consistent with the weak central coherence theory

Performance on embedded figure tests have shown that individuals with ASD are able to detect static targets hidden within complex line designs much more rapidly than typically developing observers because typically developing observers appear to analyze images in their entirety rather than focus on local elements that make up the image. Other local processing advantages in ASD have been represented in superior performance on block design tasks, the reproduction of impossible figures, visual search, the ability to learn highly confusable patterns, and performance on tasks with Navon figures that are incongruent across local and global levels of analysis.

Those with ASD are capable of global processing, but it appears that there is an automatic reliance on local information in static visual stimuli.3


Criticisms

There have been conflicting or negative findings for some tests for weak coherence in ASD. Some suggest that this may be because of differences in test-question wording; for example, when Scott et. al. asked study participants with ASD whether two lines of an illusion "looked the same length," the participants performed similarly to control groups, but when ASD participants were asked whether two lines "were the same length," they were more accurate than controls. Additionally, certain selective attention tests are particularly sensitive to small variations in methodologies. 1

Another criticism is that most tasks that test for processing assume that local and global processing levels operate antagonistically, such as in the Navon taks and the EFT. There could theoretically be other situations where the two may not necessarily act in competition with each other. 1

Some researchers have argued the need for tasks that separately examine local and global processing.3


Tests for Weak coherence

Embedded Figures Test

Block Design

Homograph Reading

Brain MRI T1 movie.gifNeuroimaging

One study found that typically developing adults who performed a bilateral visual spatial attention task showed activation in the superior parietal lobe, the left middle temporal gyrus, the left inferior and middle frontal gyri, and the medial frontal gyrus. In contrast, Autistic subjects showed activation in the bilateral ventral occipital cortex and the striate cortex. Study authors suggest that this result fits in with the idea that a defect in the neural and synaptic development produces over-connected neural systems which are prone to noise and crosstalk, which may in turn be the basis for the employment of higher cognitive processes to compensate such as weak central coherence.4

Anaphase IF.gifGenetics

Animal Models





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References

1. Happé F, Frith U. The Weak Coherence Account: Detail-focused Cognitive Style in Autism Spectrum Disorders. J Autism Dev Disord. 2006 Jan;36(1):5-25 PMID 16450045

2. Frith U, Happe F. Autism: beyond "theory of mind".Cognition. 1994 Apr-Jun;50(1-3):115-32. Review. PMID 8039356

3. Kaiser et. al. The visual perception of motion by observers with autism spectrum disorders: A review and synthesis.Psychon Bull Rev. 2009 Oct;16(5):761-77. PMID 19815780

4. Belmonte MK et. al. Functional anatomy of impaired selective attention and compensatory processing in autism.Brain Res Cogn Brain Res. 2003 Oct;17(3):651-64. PMID 14561452