Preserved recall versus impaired recognition. A case study.

A very pure and most unusual case of memory impairment is reported in a patient operated on for an aneurysm of the anterior communicating artery. Neuropsychological investigation performed about 8 yrs after the operation revealed a dissociation between very poor performance on recognition tests (on which the patient's performance was as poor as that in classical amnesic patients) and normal performance (estimated by the number of correct responses) in recall. This pattern has not previously been reported and is the reverse of that observed both in normal subjects and in amnesic patients. In addition, the patient was able to achieve a number of difficult learning tasks, at times normally; the relearning of one of these tasks after a delay of 1 h was perfectly normal. The recognition failure is interpreted in terms of the suggestion that memory performance results from an interaction between knowledge and subjective experience of remembering.