Behavioral studies on the effect of abnormal early visual experience in monkeys: temporal modulation sensitivity

Temporal modulation sensitivity functions were investigated by behavioral methods in two monkeys reared with normal visual experience and 12 monkeys reared with abnormal early visual experience. Experimental treatments were initiated when the animals were approximately one month of age. Two monkeys were each treated with one of the following procedures: (1) long-term monocular lid suture, (2) short-term monocular lid suture, (3) surgically induced esotropia, (4) surgically induced exotropia, (5) optical dissociation of binocular vision with ophthalmic prisms, or (6) chronic monocular cycloplegia. The temporal modulation sensitivity functions for uniform field flicker for both eyes of the control subjects and for the untreated eyes of the experimental subjects were similar to functions for humans measured on the same apparatus using the same behavioral procedures. All eight of the monkeys preconditioned by lid suture or surgically induced strabismus showed reduced sensitivity at all temporal frequencies with the difference between the experimental and control eyes being larger for the high than low temporal frequencies. The monkeys reared with optical dissociation of binocular vision or chronic monocular cycloplegia showed equal temporal modulation sensitivities of the two eyes, but failed to show binocular summation. It was concluded from these studies that abnormal early visual experience in monkeys results in deficiencies in the processing of both spatial and temporal information, but the differences between the treated and untreated eyes were usually greater in the spatial domain than the temporal domain.