The nature of memory impairments in multiple sclerosis: acquisition versus retrieval.

The present study was designed to examine whether verbal memory impairment in multiple sclerosis (MS) is attributable to impaired information acquisition or compromised retrieval. Twenty-three MS and 23 control subjects were administered a 10-item verbal list-learning task. Subjects were trained to a specific criterion on the verbal test in order to assure equal information acquisition. Following a 30-min delay, retrieval and recognition performance was evaluated. MS subjects required significantly more trials to reach criterion on the task relative to controls, but the groups did not differ on tests of recall and recognition. Performance was correlated with rate of information processing speed. These results suggest that verbal memory impairment among MS subjects is a consequence of inadequate initial learning and not a function of impaired retrieval.