The developing visual system: A building block on the path to autism

Abstract

Longitudinal neuroimaging studies conducted over the past decade provide evidence of atypical visual system development in the first years of life in autism spectrum disorder (ASD). Findings from genomic analyses, family studies, and postmortem investigations suggest that changes in the visual system in ASD are linked to genetic factors, making the visual system an important neural phenotype along the path from genes to behavior that deserves further study. This article reviews what is known about the developing visual system in ASD in the first years of life; it also explores the potential canalizing role that atypical visual system maturation may have in the emergence of ASD by placing findings in the context of developmental cascades involving brain development, attention, and social and cognitive development. Critical gaps in our understanding of human visual system development are discussed, and future research directions are proposed to improve our understanding of ASD as a complex neurodevelopmental disorder with origins in early brain development.

Keywords: Autism; Brain; Development; Infant; Neuroimaging.

Fig. 1

Developmental timeline of visual system differences in ASD and HL infants from birth to 24 months. Top panel (“Autism”): Differences in visual system circuitry in ASD during infancy and toddlerhood are shown (pastel orange) across the period from birth to 24 months (and beyond, indicated by arrows). General timing of the emergence of atypical visual attention and gaze behaviors (dark orange) and autistic social deficits (red) are shown for comparison. Bottom Panel (“High Likelihood”): Differences in visual system are shown for studies that compare high likelihood to typical development (blue). References for each neuroimaging study are shown as superscripts: 1. Hazlett et al., (2017)*; 2. Shen et al., (2022)*; 3. Wolff et al., (2017)*; 4. Elison et al., (2013a)*; 5. Lewis et al., (2014)*; 6. Lombardo et al., (2019); 7. Chen et al., (2022); 8. Rolison et al., (2021); 9. Nair et al., (2021); 10. Ciarrusta et al., (2020); 11. Liu et al., (2024)*. References with an asterisk indicate studies conducted on the same cohort of infants. FC = functional connectivity MRI; WM = white matter.

Fig. 2

Developmental cascade involving genetics, visual system circuitry, visual attention, and downstream brain development, cognition and behavior in ASD. In this hypothesized cascade model, genetic liability for ASD influences the development of visual circuitry that subserves atypical visual attentional and gaze behavior during infancy. Atypical visual system function and differences in visual attention create an altered visual environment for learning, impacting experience-dependent neural development and the development of higher-order brain networks that subserve cognition and social behavior, ultimately giving rise to widespread differences in brain development (e.g., brain overgrowth) and the ASD phenotype that emerges during toddlerhood.