Longitudinal Neuroimaging Study of Autism Spectrum Disorder

Sixty-three children and adolescents (38 ASD, 25 TD, 7–14 years) were recruited for this neuroimaging study at the Hospital for Sick Children (SickKids), between 2011 and 2013 (Vogan et al., 2019 (link)). All participants were invited back two years later (9–16 years) for a follow-up study. Of the 63 participants, 18 (12 ASD, 7 TD) did not return for the follow-up study due to relocation, declined to participate, had contraindications for MEG (e.g., braces), or were lost to follow-up. MEG data from 13 additional participants (10 ASD and 3 TD) were excluded from analyses due to a) sex matching; b) <20 clean MEG trials; and c) <55% task accuracy. Thus, the final sample consisted of 64 datasets from 17 children with ASD and 15 age- and sex-matched TD controls. The final sample differed slightly for the 2-back memory load condition due to increased task difficulty (58 datasets: 15 ASD, 14 TD). Importantly, as previously reported by Vogan et al. (2019) (link), the participants that returned at follow-up did not significantly differ from those who did not return in terms of age, sex, and IQ. The study protocol was approved by the Research Ethics Board at SickKids. Written informed consent was obtained by a parent or legal guardian, and informed verbal assent was provided by all children. For TD controls, exclusion criteria included a diagnosis of a learning, language or neurodevelopmental disorder; for both groups exclusion criteria also included history of prematurity, severe neurological damage, uncorrected visual impairment or colour blindness and IQ < 70. For children in the ASD group, a primary diagnosis of ASD was confirmed by the Autism Diagnostic Observation Schedule-Second Edition (ADOS-2; Lord et al., 2012 ) by expert clinicians. A summary of the demographic characteristics is shown in Table 1.Table 1

Participant demographics.

	Time point	ASD (n = 17)	TD (n = 15)	Significance test
		M (SD) or count	M (SD) or count
Sex (M:F)	Baseline	15:2	8:7	p = 0.05†
Age (years)	BaselineFollow-up	11.13 (1.83)13.50 (1.58)	10.69 (2.32)12.91 (2.29)	t(30) = 0.59, p = 0.56t(30) = 0.85, p = 0.40
ADOS-2	BaselineFollow-up	6.29 (2.05)7.13 (2.28)	–	–

†A Fisher’s exact test was used to test for differences in the proportion of boys and girls between-groups.

Full-scale IQ (FSIQ) was measured using the two sub-test version of the Wechsler Abbreviated Scale of Intelligence (WASI; Wechsler, 2013 (link)) for all children at both time points. FSIQ scores were estimated based on performance on the Vocabulary and Matrix reasoning sub-tests. To assess working memory ability, two sub-tests of the Working Memory Test Battery for Children (WMTB-C) (Gathercole & Pickering, 2000 (link)) were administered (Digit Recall and Block Recall). Parents also completed questionnaires on executive function abilities and social impairment using the Behavior Rating Inventory of Executive Function (BRIEF; Gioia et al., 2000 ) and the Social Responsiveness Scale, Second Edition (SRS-2; Constantino, 2012 ), respectively.