input when the vision is deprived. In the first 3 days they may have serious space motion sickness that will generally subside later on. When they come back, they may be becoming sick again for a weak or two to readapt to the gravity environment. Other problems such as bone density and cardiovascular function are still a subject to be investigated.
NASA is now more interested in the retinopathy (macula degeneration) that appears developed earlier in astronauts. That is where the money is, man!