Non-verbal, short-term forgetting in the alcoholic Korsakoff syndrome and Alzheimer-type dementia.

On a non-verbal, short-term forgetting task, Alzheimer patients showed a severe impairment and Korsakoff patients a more moderate impairment. At block span, less demanding of information-processing resources. Alzheimer patients were impaired and Korsakoff patients intact. The pattern of results suggested that the impairment resulted from diminished processing resources and/or an encoding or retrieval deficit, rather than from accelerated decay of the memory trace, although this latter possibility could not be completely excluded. The impairment involved memory for location or position, and there was no evidence that "short-term" memory for sequence was disproportionately affected. The deficit correlated with the degree of general, cortical atrophy evident on a CT scan and with a measure of right hemisphere dysfunction (picture arrangement errors). Together, these findings suggest that right hemisphere atrophy may underlie the deficit in non-verbal, "short-term" tests. The results are compared with those obtained in previous studies employing a verbal, short-term forgetting (Brown-Peterson) task.