Visual function of the extrageniculo-calcarine system in man: relationship to cortical blindness.

A 72-year-old woman, blind for more than two years, had normal evoked potentials to visual stimulation. Destruction of both areas 17 and relative preservation of areas 18 and 19 was demonstrated. We concluded that in the presence of bilateral destruction of area 17, visual evoked potentials are mediated by extrageniculocalcarine pathways to secondary visual cortices, but this system is not capable of providing conscious visual perception in humans.