= Sensitive period
A <sensitive period> is an interval of development during which a particular kind of experience has an unusually strong effect on subsequent behaviour or nervous-system organization. It is specific to a function and experimental outcome: susceptibility of <visual acuity> and susceptibility of a recorded <neuron>'s response need not have identical schedules. Such timing is one aspect of <neuroplasticity>.
A revealing experiment varied both the age at which a kitten's eyelids were sutured shut on one side and the duration of closure. The investigators later compared <vision> through the two eyes using graded behavioural tasks. Starting deprivation at different ages produced different lasting effects, and longer early deprivation affected more demanding tasks. This separates the timing of experience from merely its total absence.<Consequences of monocular deprivation on visual behaviour in kittens by P. B. Dews and others>[Abstract, observations 1–3: age, duration and later tests]{ref}
The same paper reported some improvement when subsequent experience forced use of the previously deprived eye, including in one older animal. A <sensitive period> can therefore coexist with later improvement. Its experimental meaning depends on the measured behaviour, the timing and duration of deprivation, and the opportunity for recovery.<Consequences of monocular deprivation on visual behaviour in kittens by P. B. Dews and others>[Abstract, observations 4–5: reversal and behavioural versus cortical measurements]{ref}
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