Autism is a prenatal disorder: Evidence from late gestation brain overgrowth.

This retrospective study aimed to specify the critical period for atypical brain development in individuals with autism spectrum disorder (ASD) using prenatal and postnatal head growth parameters. The sample consisted of 80 Caucasian, unrelated, idiopathic patients with ASD born after 1995. Fetal ultrasound parameters (head circumference [HC], abdominal circumference, and femur length) were obtained during the second and third trimesters of gestation. HC at birth and postnatal parameters at 12 and 24 months of age were also collected. Head overgrowth, assessed by HC, was highlighted during the second (20-26 weeks of amenorrhea) and third (28-36 weeks of amenorrhea) trimesters. Normal growth of body fetal parameters indicated that head overgrowth was not because of overall body overgrowth. Moreover, postnatal results replicated previously and reported head overgrowth. A critical time window for atypical brain development in autism is hypothesized to begin from the 22nd week of amenorrhea. This period is critical for cortical lamination and glial activation. A pathophysiological cascade is suggested with interactions between candidate genes and environmental factors. Autism Research 2018, 11: 1635-1642. © 2018 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: It is now widely acknowledged in the scientific community, that autism is a neurodevelopmental disorder. Recent evidence from animal and pathological studies has implicated the in utero period. However, the precise time of onset of abnormal brain development remains unknown. This retrospective study reports novel findings, identifying an atypical head growth trajectory in children with autism, during the in utero period (after the 22nd week of amenorrhea). In the same children, postnatal head overgrowth was also observed. Late gestation is identified as a critical period for atypical brain development underlying autism symptoms.

Back to basic: do children with autism spontaneously look at screen displaying a face or an object?

Eye-tracking studies on exploration of faces and objects in autism provided important knowledge but only in a constraint condition (chin rest, total time looking at screen not reported), without studying potential differences between subjects with autism spectrum disorder (ASD) and controls in spontaneous visual attention toward a screen presenting these stimuli. This study used eye tracking to compare spontaneous visual attention to a screen displaying a face or an object between children with autism and controls in a nonconstraint condition and to investigate the relationship with clinical characteristics in autism group. Time exploring screen was measured during passive viewing of static images of faces or objects. Autistic behaviors were assessed by the CARS and the BSE-R in autism group. In autism group, time exploring face screen and time exploring object screen were lower than in controls and were not correlated with degree of distractibility. There was no interaction between group and type of image on time spent exploring screen. Only time exploring face screen was correlated with autism severity and gaze impairment. Results highlight particularities of spontaneous visual attention toward a screen displaying faces or objects in autism, which should be taken into account in future eye-tracking studies on face exploration.