Answer: The optic lobe gives the sense of vision. The large size of the optic lobe of a frog brain suggests that the major part of processing in the brain of frogs is associated with vision.
In other words, frogs require to process large amount of visual information ( sent by retina via optic nerve) very quickly and effectively. Large and bulging eyes are very sensitive to movements and have excellent night vision. They can visualize things in front, to their sides, partially behind.
Thus, large optic lobe of a frog brain provides great significance to them.
