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Highlights
•
This longitudinal study uses direct measurements of testosterone and lateralization.
•Both prenatal and pubertal testosterone relate to brain lateralization.
•The influence of testosterone differs between right- and left-lateralized tasks.
•These results may explain discrepancies in the current literature.
•We provide a new hypothesis based on androgen receptor distribution and efficiency.
Abstract
After decades of research, the influence of prenatal testosterone on brain lateralization is still elusive, whereas the influence of pubertal testosterone on functional brain lateralization has not been investigated, although there is increasing evidence that testosterone affects the brain in puberty. We performed a longitudinal study, investigating the relationship between prenatal testosterone concentrations in amniotic fluid, pubertal testosterone concentrations in saliva, and brain lateralization [measured with functional Transcranial Doppler ultrasonography [fTCD]] of the Mental Rotation, Chimeric Faces and Word Generation tasks. Thirty boys and 30 girls participated in this study at the age of 15 years. For boys, we found a significant interaction effect between prenatal and pubertal testosterone on lateralization of Mental Rotation and Chimeric Faces. In the boys with low prenatal testosterone levels, pubertal testosterone was positively related to the strength of lateralization in the right hemisphere, while in the boys with high prenatal testosterone levels, pubertal testosterone was negatively related to the strength of lateralization. For Word Generation, pubertal testosterone was negatively related to the strength of lateralization in the left hemisphere in boys. For girls, we did not find any significant effects, possibly because their pubertal testosterone levels were in many cases below quantification limit. To conclude, prenatal and pubertal testosterone affect lateralization in a task-specific way. Our findings cannot be explained by simple models of prenatal testosterone affecting brain lateralization in a similar way for all tasks. We discuss alternative models involving age dependent effects of testosterone, with a role for androgen receptor distribution and efficiency.
Keywords
Puberty
Cognitive function
Brain asymmetry
Laterality
FTCD
Sex hormones
Cited by [0]
© 2017 The Authors. Published by Elsevier Ltd.
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Under a Creative Commons license
Open access
Highlights
•
Prenatal exposure to high levels of fetal testosterone [FT] is a proposed theory for autism.
•The 2D:4D reflects this exposure prenatally.
•It is a case–control study conducted with 60 male children.
•31 individuals have classic-onset autism and 29 individuals serve as age-matched, healthy controls.
•The results showed that the 2D:4D was significantly lower in boys with autism compared to the controls [p ≤ 0.001].
Abstract
Background
Autism is a neurodevelopment disorder with a strikingly higher prevalence in boys than girls. There are many theories regarding this gender bias, and prenatal exposure to high levels of fetal testosterone [FT] may be a predisposing factor. The second to fourth digit ratio [2D:4D] is the only indirect measure that reflects this association postnatally. Thus, this study measured the lengths of the index finger [2D] and the ring finger [4D] and calculated the 2D:4D ratio. Subsequently, this ratio was used to indirectly determine the potential prenatal exposure to high levels of FT in autistic children.
Methods
This case–control study was conducted with 60 male children with 31 individuals having classic-onset autism and 29 individuals serving as age-matched, healthy controls. The lengths of both the index [2D] and the ring [4D] fingers of the right hand of both autism and control groups were obtained using a scanner and the 2D:4D ratio was calculated.
Results
The 2D:4D ratio in the current study was significantly lower in boys with autism compared to the controls [p ≤ 0.001].
Conclusions
This study demonstrates a significantly lower 2D:4D ratio in Saudi boys with autism, which indirectly suggests that these boys were exposed to high levels of prenatal FT. Accordingly, prenatal exposure to high levels of FT is a risk factor for the development of autism, and the postnatal measurement of the 2D:4D ratio could be a potential screening tool.
Keywords
Autism
Digit ratio
Fetal testosterone
Cited by [0]
Copyright © 2015 The Authors. Published by Elsevier Ireland Ltd.