Dorsal and ventral visual streams: Typical and atypical development

The literature on visuospatial processing describes two distinct pathways within the brain: a dorsal route extending from the visual cortex into the parietal lobes that is critical for spatial processing and a ventral route extending from the visual cortex into the temporal lobes that is critical for form perception. These visual streams appear to differ in their developmental trajectories and their vulnerabilities to diverse neurodevelopmental conditions. The present work aims to investigate development and vulnerability in two aspects of dorsal and ventral visual-stream function, namely attention to location and attention to identity. In Study 1, we compare typically-developing (TD) youth aged 9 to 16 years with young adults aged 18 to 22 years on computerized location and identity tasks. In Study 2, we compare children and adolescents who have congenital hypothyroidism (CH), a pediatric endocrine disorder, with age-matched TD controls on the same tasks. The results from Study 1 show that the youths were less accurate than the adults at judging identity, whereas both groups were equally accurate at judging location. The results from Study 2 show that the youths with CH were slower but not less accurate than the TD youths in making both identity and location judgments. The results are interpreted as signifying later development of ventral (identity) stream functions compared to dorsal (location) but equal vulnerability of both functions in CH.