Recognition of visual letter strings following injury to the posterior visual spatial attention system

Abstract

Unilateral posterior lesions often produce a deficit in visual spatial attention. One result of this deficit is a loss of information from a word contralateral to the lesion when presented simultaneously with an ipsilateral word (interword extinction). However, when a single word presented at fixation covers the same visual angle there is frequently no extinction (Sieroff & Michel, 1987). Why are centred words not extinguished? Our studies attempt to discover the reason by comparing centred word and nonword letter strings. Nonwords do show extinction. Words are processed more accurately and show little evidence of extinction. Compound words appear to act like normal words, but segmenting letters into separate strings increases extinction. These results suggest that spatial attention is unnecessary for access to the lexical network that produces a visual word form.