Questioning the “Critical Period”

Received wisdom says that there is a critical period after birth during which the brain is wired for sight; blindness then means blindness for life. But a new study challenges this wisdom by demonstrating that congenitally blind children up to the age of 15 years can experience substantial vision gains.

By Mark Hillen

In 1963, David Hubel and Torsten Wiesel, discovered that cats that had one eye sewn shut from birth to three months of age only developed full vision in the open eye (1), and that monocular deprivation caused permanent electrophysiological and anatomical changes in the cats’ brains. Sewing the eye closed after three months of age did not have this effect, so the immediate postnatal three months was named the “critical period” for vision development.

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