Nature 360, 461 - 463 (03 December 1992); doi:10.1038/360461a0

Possible blindsight in infants lacking one cerebral hemisphere

Oliver Braddick^*, Janette Atkinson^*, Bruce Hood^*, William Harkness^†, Graeme Jackson^† & Faraneh Vargha-Khademt^†

^*Visual Development Unit, Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, UK
^†Hospital for Sick Children and Institute for Child Health, Great Ormond Street, London WC1, UK

PATIENTS with damage to the striate cortex have a subjectively blind region of the visual field, but may still be able to detect and localize targets within this region^1,2. But the relative roles in this 'blindsight' of subcortical neural systems, and of pathways to extra-striate visual areas, have been uncertain³. Here we report results on two infants in whom one cerebral hemisphere, including both striate and extra-striate visual cortex, needed surgical removal in their first year. Single conspicuous targets in the half-field contralateral to the lesion could elicit fixations, implying detection and orienting by a subcortical system. In contrast, binocular optokinetic nystagmus (OKN), for which a subcortical pathway has often been thought adequate, showed a marked asymmetry. In normal neonates, fixation shifts and OKN have both been taken to reflect subcortical control⁴; our results are consistent with subcortical control for fixation but not for OKN.

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