Digit span and visual neglect: a puzzling relationship.

Weinberg et al. found a relationship between the presence of extinction and the discrepancy between backward and forward digit span among left hemiplegic patients. The present study replicates this finding in a group of 37 patients suffering from unilateral left visual neglect, demonstrating a strong relationship between degree of neglect and digit span discrepancy. A principal components analysis of a neurospychological examination revealed three main independent components--Neglect, Verbal Memory and Non-verbal Memory respectively. Digit Span Discrepancy had one of the highest loadings on the neglect factor, and loaded significantly on no other factor. Multiple regression analysis showed that the relationship of Digit Span Discrepancy with Degree of Neglect exists independently of visuo-spatial ability, and this is also true for paced auditory serial addition (PASAT) scores for one of the two main indices of neglect. The implications of this for understanding neglect are discussed.