Autism, lateralization, and handedness: a review of the literature and meta-analysis Open Access

Preslar, Jessica Paige (2012)

Permanent URL: https://etd.library.emory.edu/concern/etds/z603qz359?locale=en
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Abstract

Abstract
Autism, lateralization, and handedness: a review of the literature and meta-analysis


A number of theories of hemispheric lateralization and autism have hypothesized a link between the disorder and asymmetries in the brain. Research has been conducted to investigate this connection, but different methods and definitions have been used and the results vary widely. A systematic review and meta-analysis was conducted to assess the literature on this subject, with the hypothesis that there would be an association between autism and laterality that would be moderated by handedness, sex, age, brain region studied, and level of autism. From a broad search resulting in 259 papers, 54 were identified for inclusion in the literature review. This was narrowed further to include only studies reporting results in the inferior frontal gyrus for a meta-analysis, resulting in 4 papers. Reviewing the literature found that the majority of studies found some difference in lateralization between the autistic and control group, although what the difference was varied widely. Trends also suggested moderating variables did not have a strong influence on this relationship, although poor data quality and underrepresentation of some groups made this difficult to assess. The meta-analysis also found a moderate but non-significant effect size of group on lateralization, suggesting a decrease in the strength of lateralization in the autistic group. A subgroup analysis of sex and a meta-regression of handedness showed that these moderating variables did not have a significant effect on the relationship of autism and lateralization. Although the results are not conclusive, there appears to be a general trend towards a relationship between autism and lateralization. However, more rigorous studies with better controls and clearer reporting of definitions and results are needed.

Table of Contents

Table of Contents
Introduction...pg 1-5
Methods...pg 5-15
Results...pg 15-22
Discussion...pg 22-34
References...pg 35-41
Appendix A: Variables...pg 42-43
Appendix B: Brain Regions...pg 44


Tables and Figures
Figure 1: Study selection...pg 5
Table 1: Study characteristics...pg 19-20
Figure 2: Summary effect size...pg 20
Figure 3: Publication bias...pg 21
Figure 4: Meta-regression of handedness...pg 22

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