In a patient suffering from a severe bilateral dysfunction in both occipital and parietal areas we have found: (1) A loss of contrast-sensitivity, being strongest in the range of spatial frequencies where the normal eye is most sensitive; (2) Virtually normal grating resolution, a severe loss in letter acuity (about 15-fold), and a very strong loss in vernier acuity (about 100-fold); (3) Rapid partial recovery of contrast sensitivity due to stimulation; (4) Slow partial recovery of letter acuity due to CAM rotating grating treatment; (5) No improvement of a 10-fold temporal retardation in the speed of reading. Evidence is presented that the residual impairment of vision depends upon improper synthesis of spatial frequency components originating from a heavy loss in processing speed and abnormally long store duration for high spatial frequency information.
