Interocular interactions in macaque LGN

[摘要] Some of the most common visual disorders, such as amblyopia and stereoblindness, affect binocular vision. However, our understanding of how the brain processes binocular inputs is limited. Here we investigate where the signals from the two eyes first interact in the primary visual pathway in primates with normal binocular vision. The LGN is the first structure in this pathway receiving inputs from both eyes, with neighboring layers receiving exclusive inputs from one retina or the other. While the vast majority of neurons in the LGN are driven by stimulation of one eye only, it is unclear to what degree responses of LGN neurons depend on what is viewed by both eyes. In the primary visual cortex (V1), the next stage in the primary visual pathway, the vast majority of neurons respond to either eye, with one eye often evoking stronger responses than the other. In this study, we test the hypothesis that interocular interactions occur prior to spiking in V1. We trained macaque monkeys to fixate on a computer screen. Using a linear multicontact electrode array, we recorded LGN spiking responses to drifting gratings that varied in contrast and were presented to one or both eyes. Then, we compared contrast response functions under monocular and binocular stimulation conditions. We observed that the firing rate of a minority of LGN neurons, exclusive to the magnocellular layers, modulated under binocular stimulation. These effects included both binocular suppression and facilitation. We will discuss these results with regard to interocular anatomical connections in the primate early visual system.

[学科分类] 眼科学