LANGUAGE NETWORKS IN ASD: Hemispheric Lateralization of Language Processing in Autism Spectrum Disorders – a Functional Connectivity Approach

Abstract

Hemispheric specialization for language occurs early in life and it is typically left-lateralized. Recent studies investigating functional connectivity underlying Autism Spectrum Disorders (ASD) have shown that the atypical lateralization patterns of Broca area, Wernicke area, and more recently, of the cerebellum (i.e. less left-lateralized or right-lateralized) might be associated with the language and communication impairments this population suffers from. To further investigate whether functional connectivity associated to language processing differed between ASDs and neurotypicals, separate resting-state fMRI analyses were implemented in the bilateral and unilateral seeds that were placed in Broca area, Wernicke area, and Crus I of the cerebellum. Between-seed analyses were run on the connectivity matrices that were built for each group using the time series correlations of those seeds. And, sensitivity analyses were used to correct for the influence IQ, handedness or both might have exerted on brain lateralization. Additionally, to test whether the intrahemispheric FC of the left and right brain hemisphere differed between groups, a FC laterality index (LI) was computed only in the unilateral seeds. Results revealed the FC between the seed-pairs placed on (left) Broca and Wernicke area was decreased, whereas FC between right Wernicke area and the left cerebellum was increased. Moreover, sensitivity analyses revealed participants' IQ or handedness did not affect FC of those seed-pairs, suggesting these might be intrinsic to ASD. Contrary to expectations, no evidence was found to suggest atypical hemispheric brain lateralization might be intrinsic to ASD. No significant differences were found between the intrahemispheric FC of the left and right brain hemisphere.