Oh maybe I misinterpreted. I thought the author was arguing that the purpose of sleep was this protection of the visual cortex, but maybe the idea is that slee

Oh maybe I misinterpreted. I thought the author was arguing that the purpose of sleep was this protection of the visual cortex, but maybe the idea is that sleep has another purpose (with varying timing thoughout the day depending on the animal) and the purpose of dreams is to protect the visual cortex while this is going on.