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Sendy Caffarra, Sung Jun Joo, David Bloom, John Kruper, Ariel Rokem, Jason D. Yeatman; Development of the visual pathways predicts changes in electrophysiological responses in visual cortex. Journal of Vision 2021;21(9):2127. doi: https://doi.org/10.1167/jov.21.9.2127.
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© ARVO (1962-2015); The Authors (2016-present)
The latency of neural responses in visual cortex varies dramatically among individuals and changes systematically across the lifespan. Does maturation of the visual pathways predict changes in electrophysiology? Here we test the hypothesis that development of the optic radiations mediates developmental changes in conduction velocities of visual signals. Thirty-eight children participated in a cross-sectional study including a diffusion MRI and an MEG session (17 females, mean age: 9.5 y, SD: 1.6, age range: 7-12 y, between-sessions time gap: 0-35 dd). During the MEG acquisition participants were presented with a sequence of high and low contrast visual stimuli (HC and LC), including words and noise patches. A fixation and a lexical decision task were performed on the same stimuli in alternating runs. For all stimulus types and tasks, early evoked fields were observed around 100 ms after stimulus onset (M100), with a reduced amplitude and longer latency for low as compared to high contrast images. The left and right optic radiations (OR) was identified in each individual’s brain based on anatomically constrained probabilistic tractography and mean fractional anisotropy (FA) was calculated for each pathway. OR FA predicted electrophysiological characteristics of M100 responses, and this was particularly clear in high contrast stimuli: the greater the OR FA the faster the M100 latency and the bigger its amplitude. Moreover, a time-frequency decomposition of the M100 response revealed that participants with higher OR FA had greater power and inter-trial coherence. Examining changes over this developmental window, the M100 peak latency to HC became faster with age and the FA of the optic radiation fully mediated this effect. Similar FA mediation effects were found for the M100 amplitude and power. These findings suggest that development of the optic radiation over childhood accounts for individual differences in the developmental trajectory observed in early visual evoked responses.
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