Focusing on/in visual-verbal stimuli in patients with parietal lesions

Abstract

Patients with parietal lesions have been shown to exhibit the phenomenon of visual-verbal extinction between letter strings (when presented with pairs of verbal stimuli) and within a letter string (when presented with multiple, unrelated letters, as in nonwords). A group study is reported with patients suffering from right or left parietal lesions. It is shown that although patients with right lesions show reasonably consistent left extinction with bilateral presentation of nonwords (centred or pairs), patients with left parietal lesions show quite puzzling results: they may present more extinction with pairs of short nonwords than with long centred nonwords; also, the side of extinction is not systematically on the side contralateral to the lesions. A case study is presented of a patient suffering from a left parietal lesion, who shows extinction with pairs of short nonwords but not with centred nonwords. It is argued that he may show a specific deficit in focusing on (selecting) one visual-verbal stimulus, when it is presented with other visual-verbal stimuli. Some hypotheses are developed concerning the different visuo-spatial processes occurring in reading.