Brain asymmetries in autism and developmental language disorder: a nested whole-brain analysis

Abstract

We report a whole-brain MRI morphometric survey of asymmetry in children with high-functioning autism and with developmental language disorder (DLD). Subjects included 46 boys of normal intelligence aged 5.7-11.3 years (16 autistic, 15 DLD, 15 controls). Imaging analysis included grey-white segmentation and cortical parcellation. Asymmetry was assessed at a series of nested levels. We found that asymmetries were masked with larger units of analysis but progressively more apparent with smaller units, and that within the cerebral cortex the differences were greatest in higher-order association cortex. The larger units of analysis, including the cerebral hemispheres, the major grey and white matter structures and the cortical lobes, showed no asymmetries in autism or DLD and few asymmetries in controls. However, at the level of cortical parcellation units, autism and DLD showed more asymmetry than controls. They had a greater aggregate volume of significantly asymmetrical cortical parcellation units (leftward plus rightward), as well as a substantially larger aggregate volume of right-asymmetrical cortex in DLD and autism than in controls; this rightward bias was more pronounced in autism than in DLD. DLD, but not autism, showed a small but significant loss of leftward asymmetry compared with controls. Right : left ratios were reversed, autism and DLD having twice as much right- as left-asymmetrical cortex, while the reverse was found in the control sample. Asymmetry differences between groups were most significant in the higher-order association areas. Autism and DLD were much more similar to each other in patterns of asymmetry throughout the cerebral cortex than either was to controls; this similarity suggests systematic and related alterations rather than random neural systems alterations. We review these findings in relation to previously reported volumetric features in these two samples of brains, including increased total brain and white matter volumes and lack of increase in the size of the corpus callosum. Larger brain volume has previously been associated with increased lateralization. The sizeable right-asymmetry increase reported here may be a consequence of early abnormal brain growth trajectories in these disorders, while higher-order association areas may be most vulnerable to connectivity abnormalities associated with white matter increases.

N-acetyl aspartate in autism spectrum disorders: Regional effects and relationship to fMRI activation

“…This finding suggests that voxel placement may determine whether neural abnormalities will be observed in ASD. Other brain imaging studies which investigated the frontal lobes in their entirety have also consistently found abnormalities such as reversed asymmetries in language association areas (Herbert et al, 2005), decreased metabolism (Zilbovicius et al, 1995), abnormal patterns of activation (Just et al, 2004;Luna et al, 2002;Muller et al, 2003;Pierce et al, 2004;Silk et al, 2006), and white matter abnormalities (Barnea-Goraly et al, 2004;Carper et al, 2002;Herbert et al, 2004). As such, while ASD almost certainly involves frontal lobe abnormalities, the exact nature of the abnormalities requires further characterization.…”

“…Structural neuroimaging studies of individuals with Autistic Disorder, who among individuals with ASD have the highest level of autistic symptomatology and the lowest level of adaptive functioning (Walker et al, 2004), have reported widespread abnormalities including agedependent increased brain volume (Aylward et al, 2002;Courchesne et al, 2001;Hazlett et al, 2005;Redcay and Courchesne, 2005;Sparks et al, 2002) reduced size of vermal lobules VI and VII (Ciesielski et al, 1997;Courchesne et al, 1994a;Courchesne et al, 1988;Hashimoto et al, 1995;Kaufmann et al, 2003), and reversed patterns of asymmetry (Herbert et al, 2005).…”

The impact of asymmetrical light input on cerebral hemispheric specialization and interhemispheric cooperation

“…Accordingly, even profoundly lateralized cognitive functions, such as speech processing, benefit from efficient interhemispheric communication 2 . On the other hand, developmental disorders like autism 3 , dyslexia 4 or schizophrenia 5 are characterized by untypical cerebral lateralization patterns as well as structural peculiarities of the corpus callosum that are related to cognitive impairments [6][7][8][9][10] . Although several studies suggest a relationship between functional lateralization and structural organization of commissural systems, for example 11,12 , the functional and developmental relationships remain controversial 13 .…”

Aberrant neural networks for the recognition memory of socially relevant information in patients with schizophrenia

“…These results supported our opinion that the compensatory activity in the right superior temporal lobe in the patients indicated the decreased connectivity of that region. Generally, a dominance of the left hemisphere in language‐related areas was observed, which was in accordance with the results of previous studies of healthy controls only (Galaburda, LeMay, Kemper, & Geschwind, 1978) or healthy controls and patients with language disorders (Herbert et al., 2005). However, other studies of healthy controls have reported results that demonstrate right lateralization of the language comprehension network, even though the motor speech network is still lateralized to the left (Zhu et al., 2014).…”