Attenuated and delayed neural activity in cortical microcircuitry of monocular processing and binocular interactions in human amblyopia

Disruption of retinal input early in life can lead to amblyopia, a condition characterized by reduced visual acuity after optical correction. Although functional abnormalities of amblyopia have been found in the early visual areas, mesoscale deficits in the cortical microcircuitry across cortical depth remain unexplored in humans. Using a combination of submillimeter 7T fMRI and EEG frequency-tagging methods, we investigated the neural deficits in monocular processing and binocular interactions in human adults with unilateral amblyopia. Results showed attenuated and delayed monocular activity in the thalamic input layers of V1, followed by imbalanced binocular suppression and weakened binocular integration in the superficial layers, which further reduced the visual signal strength and processing speed. These findings reveal the precise neural deficits in the cortical microcircuitry in human amblyopia, providing important insights into the mesoscale mechanisms of developmental plasticity and may help to develop more effective treatments for the visual disorder.