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Paul Martin, Natalie Zeater, Soon Keen Cheong, Samuel Solomon, Alexander Pietersen, Bogdan Dreher; Binocular inputs to single neurons in primate lateral geniculate nucleus. Journal of Vision 2014;14(15):31. doi: 10.1167/14.15.31.
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Parvocellular (P) and magnocellular (M) neurons in the dorsal lateral geniculate nucleus (LGN) receive excitatory input from one eye (monocular). The organization of binocular inputs to koniocellular (K) pathway neurons remains largely unexplored. Here, we recorded from the LGN of sufentanil anaesthetized marmoset monkeys (Callithrixjacchus, n=3). A NeuroNexus 32-channel silicon probe was used to record extracellular single cell activity in response to pulsed achromatic and cone-isolating visual stimuli. Large-field (12 deg. diameter) stimuli were presented monocularly to each eye, or binocularly. Cells were classified by analysis of response properties and, in most cases, by anatomical reconstruction of recording sites. Strength of functional input from the non-dominant eye (0 = no input; 0.5 = equal strength of input from each eye) and sign (+ = excitation; - = suppression) was measured at the time of peak excitatory response from the dominant eye. We found as expected only weak non-dominant eye inputs to P cells (n=16, mean −0.02, SD 0.12) and M cells (n=13, mean 0.05, SD 0.07). Overall the strength of non-dominant inputs to K cells (n=51) was greater (mean 0.14) and more variable (SD 0.20). Weight of inputs to “blue-on” K cells (n=17) ranged from −0.15 to +0.33 (mean 0.05, SD 0.16). “Suppressed-by-contrast” K cells (n=5) and 3/5 “On-Off” K cells showed almost identical responses to stimuli delivered through either eye. We conclude that many K cells receive excitatory input from both eyes, and therefore are a site for subcortical binocular integration.
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