= Critical period
A <critical period> in neural development is a bounded interval in which particular experiences have a strong role in establishing a specified function or circuit organization. Its timing must be stated for a species and a measured outcome. A <sensitive period> emphasizes heightened susceptibility without necessarily asserting that every later change is impossible.
A classic example comes from <monocular deprivation> in <cats>. <P. B. Dews> and colleagues closed one <eye> at different ages and for different durations, then compared <vision> through the two <eyes> when the animals were at least a year old. Starting deprivation at one month offered little protection against lasting impairment; starting at two months reduced the impairment, and starting at four months or later produced no lasting deficit detectable in their behavioural tests. The age comparison revealed a developmental window rather than merely a short-lived effect of having an <eye> closed.<Consequences of monocular deprivation on visual behaviour in kittens by P. B. Dews and others>[Journal of Physiology 206, pp. 437–455; abstract points 1–3, starting age, duration and delayed behavioural testing]{ref}
The design separates \b[age at disruption], \b[duration of disruption], and \b[the function tested]. A change in <visual acuity> and a change in the responses of <visual cortex> <neurons> need not have identical recovery profiles. The existence of a <critical period> for one visual measure does not establish a single deadline for the entire <brain>, or the absence of adult <neuroplasticity>.<Consequences of monocular deprivation on visual behaviour in kittens by P. B. Dews and others>[Abstract points 4–5; behavioural improvement and cortical responses after reversal of eye closure]{ref}
Back to article page
