视觉是人和多数动物最重要的感知，它发端于光量子在视网膜上的时空分布图景。昼夜亮度信息通过眼睛进入脑内，促使动物的生理和行为与昼夜节律同步，例如睡眠/觉醒循环。鸟类是唯一单眼闭合即半脑睡眠的陆生脊椎动物。鉴于鸟类双眼侧置，视神经完全交叉，眼间骨透明，我们推测鸟类在半脑睡眠时，环境光首先刺激睁眼视网膜的本体感光神经节细胞，继而激发视杆/视锥细胞，剩余光线透过眼间骨作用于闭眼的视杆/视锥细胞，两眼接收的光能信息通过脑内亮度编码细胞发挥重要的生理作用。本课题以家鸽为模型，用不同强度的光或亮/暗循环分别或同时刺激两眼，在视觉丘脑、视交叉上核和顶盖前区做单细胞记录，以揭示亮度编码神经元在光周期同步和半脑睡眠中的作用；并将埋植电极记录与动物行为相结合进一步为单细胞反应提供行为学意义。预实验表明，眼间透射光有重要生理意义，亮度编码细胞的放电活动能与外界亮/暗周期刺激同步，并记忆和回放光周期同步的放电模式。

Vision is the most important one of all sensory perceptions in humans and most animals, and it originates from the spatial and temporal distribution patterns of incident photons on retinal surface. Information about daily changes in ambient luminance is received by the brain through the eyes, resulting in photoentrainment of physiology and behaviors of animals to the day/night cycle, e.g. sleep/wake cycle. Birds are the only class of terrestrial vertebrates that has a sleep with one eye closed, i.e. unihemispheric sleep. Owing to that avian eyes are laterally positioned, the optic nerves completely cross to the contralateral hemisphere, and interocular cartilage is transparent, we would suggest that during unihemispheric sleep, ambient light first stimulates intrinsically photosensitive retinal ganglion cells and then rod/cone cells in the open eye, and the remaining light shines through interocular tissues to activate rod/cone cells in the closed eye, thereby photic information picked up by both eyes would play essential physiological roles via luminance encoding neurons in the brain. The present project would use the pigeon as a model, in which single cell recordings are made from the visual thalamus, the suprachiasmatic nucleus and the pretectal area while individual or both eyes are stimulated with light of various intensities or light/dark cycle stimuli, aiming at revealing the functional significance of luminance encoding neurons in photoentrainment and unihemispheric sleep. A combination of recording neuronal activity with an implanted electrode array and videography of behaviors of animals would provide behavioral significance of these cell-level findings. Preliminary experiments have shown that interocular light transmission would play essential roles in physiology, and the firing activity of luminance encoding neurons could be entrained to external light/dark cycle stimuli，and they can memorize and replay their own entrained firing patterns.