Monocular deprivation

Monocular deprivation is an experimental reduction of normal patterned vision through one eye while the other remains available. It is used to investigate how sensory experience shapes a developing nervous system. In classic cat experiments, researchers closed the eyelids of one eye for a stated interval, then reopened it and compared what the animal could do through each eye.^[ref]

P. B. Dews and colleagues varied both the starting age and duration of deprivation, testing the cats when they were at least a year old. Closure during the first four to six weeks left a lasting reduction in visual acuity. Longer early closure could also impair visually guided paw placement and pattern discrimination. Deprivation beginning at four months or later produced no lasting deficit detectable by their behavioural tests. The comparison identifies a critical period of heightened susceptibility in this species and experimental setting; it does not mean that all forms of adult neuroplasticity disappear.^[ref]

An illuminating feature of the design is its separation of when experience is lost from how long it is lost. A weak response immediately after opening an eye would not alone demonstrate a lasting developmental change; delayed testing and comparison with the other eye make that inference stronger.