Neuroanatomic and neuropsychologic correlates of digit span performance by brain-damaged adults

Digit repetition performance was examined in samples of adult brain-injured patients having confirmed unilateral lesions. The primary purposes of the study were to investigate the sensitivity of forward and backward repetition to the effects of lateralized brain lesions and to assess the differential neuroanatomic and neuropsychologic substrates of the two forms of digit repetition. Digit repetition, especially digits backward and particularly by patients with left-hemisphere lesions, was significantly lower than would be predicted on the basis of intelligence. However, impaired repetition was not invariably a consequence of brain damage. Correlational data suggested but could not confirm hypotheses about either the functional or the neuroanatomic substrate in differential performance on digits forward and backward. Problems implicit in using measures having a high intellectual loading in clinical studies are discussed, as are suggestions for further research.