Visual functions without the occipital lobe or after cerebral hemispherectomy in infancy

This paper investigates whether and to what extent vision with awareness is still possible in the whole visual field after loss of the occipital lobe of one or both cerebral hemispheres or after hemispherectomy in childhood. The visual functions of four children who suffered from unilateral or bilateral loss of the occipital lobe or who had been hemispherectomized were examined. The results show that even after unilateral loss of the striate and prestriate cortex the extent of the visual field may still be in the normal range. The residual visual functions may be mediated by intact extrastriate areas such as V5 and LO of the damaged cerebral hemisphere. It is also shown that even after complete hemispherectomy in early life the visual field may have a normal extent and that conscious visual perception in the whole visual field may be preserved. In hemispherectomized children, the remaining cerebral hemisphere or neural structures in the midbrain, including the superior colliculi and the praetectum, may be able to mediate these visual functions.