TY - JOUR T1 - Interocular Suppression in Primary Visual Cortex in Strabismus JF - The Journal of Neuroscience JO - J. Neurosci. DO - 10.1523/JNEUROSCI.0044-21.2021 SP - JN-RM-0044-21 AU - John R. Economides AU - Daniel L. Adams AU - Jonathan C. Horton Y1 - 2021/05/03 UR - http://www.jneurosci.org/content/early/2021/05/03/JNEUROSCI.0044-21.2021.abstract N2 - People with strabismus acquired during childhood do not experience diplopia (double vision). To investigate how perception of the duplicate image is suppressed, we raised two male monkeys with alternating exotropia by disinserting the medial rectus muscle in each eye at age 4 weeks. Once the animals were mature, they were brought to the laboratory and trained to fixate a small spot while recordings were made in V1. Drifting gratings were presented to the receptive fields of 500 single neurons for 8 interleaved conditions: 1) right eye monocular, 2) left eye monocular, 3) right eye’s field, right eye fixating, 4) right eye’s field, left eye fixating, 5) left eye’s field, right eye fixating, 6) left eye’s field, left eye fixating, 7) both eyes’ fields, right eye fixating, 8) both eyes’ fields, left eye fixating. As expected, ocular dominance histograms showed a monocular bias compared with normal animals, but many cells could still be driven via both eyes. Overall, neuronal responses were not affected by switches in ocular fixation. Individual neurons exhibited binocular interactions, but mean population indices indicated no net interocular suppression or facilitation. Even neurons located in cortex with reduced cytochrome oxidase activity – representing portions of the nasal visual field where perception is suppressed during binocular viewing – showed no net inhibition. These data indicate that V1 neurons do not appear to reflect strabismic suppression and therefore the elimination of diplopia is likely to be mediated at a higher cortical level.SIGNIFICANCE STATEMENTIn patients with strabismus, images fall on non-corresponding points in the two retinas. Only one image is perceived, because signals emanating from the other eye that convey the duplicate image are suppressed. The benefit is that diplopia is prevented, but the penalty is that the visual feedback required to adjust eye muscle tone to realign the globes is eliminated. Here we report the first electrophysiological recordings from the primary visual cortex in awake monkeys raised with strabismus. The experiments were designed to reveal how perception of double images is avoided. ER -