In behavioral experiments rhesus macaque monkeys were trained to interact with the computer using a tactile display. We used grayscale Gabor patches of low spatial frequency as stimuli. Monkeys' task was to touch the screen with his hand in the area of the target stimulus, followed by automatic food or juice reinforcement. After two successive correct answers, stimulus contrast gradually decreased. Using a two-alternative forced choice method the contrast threshold was measured within which monkeys can detect the appearance of low-frequency images. It was shown that the contrast sensitivity decreased with the decrease of stimulus spatial frequency, while the reaction time increased. The findings extend our knowledge of the primates' activity in the virtual environment and open new possibilities for modeling and studying various human diseases.