We have studied the contrast sensitivity of the visual system in various ranges of the spatial frequencies in “dry” immersion conditions that simulate the physiological effects of microgravity. The contrast sensitivity in the range of low and high spatial frequencies is indicative of the functional state of the magnocellular and parvocellular neuronal pathways that form the dorsal and ventral information flows from the occipital to the frontal lobes. The study involved ten volunteers who were exposed to “dry” immersion for 21 days. The contrast sensitivity of the visual system was recorded with a method of visocontrastometry. The Gabor elements were used as stimuli. An increase in contrast sensitivity was registered in the low spatial frequency range with specific sensitivity of the magnocellular pathway to these frequencies on the third day of immersion and 1 day after the end of the experiment, compared to the background values. The contrast sensitivity in the high spatial frequency range with specific sensitivity of the parvocellular pathway to these frequencies in the experiment remained unchanged. Thus, our findings have shown that the magnocellular neuronal pathway is involved in the processes of adaptation to extreme ambient conditions.