Verbal and non-verbal short-term memory impairment following hemispheric damage

Short-term memory was investigated in 30 control and 125 unilaterally brain-damaged patients with a series of tests requiring the immediate reproduction of strings of items of increasing length. In three tests the items were auditorially presented digits or words: one test asked for oral repetition of digits, while the other two required the patient to point to written digits or to pictures. The fourth test aimed at measuring spatial span. On both the Digits Forward test and the two other verbal tests not requiring the use of speech, left brain-damaged patients were impaired in comparison to normals, while the right brain-damaged patients were not. Aphasics had a significantly shorter verbal span than non-aphasic patients with left hemisphere damage. Spatial span, on the other hand, was significantly affected by a lesion posteriorly located in either hemisphere, but not by aphasia. Two patients with an exceedingly poor verbal memory span were observed, one suffering from anomic aphasia and the other from conduction aphasia. There were also two right hemisphere damaged patients who showed an extreme reduction of spatial span, which could not be accounted for by space perceptual disorders and contrasted with a normal performance on a spatial long-term memory test.