Dissociation between recall and recognition memory in amnesia: The case of a patient with hippocampal damage following carbon monoxide poisoning

There is currently a debate regarding the status of recall and recognition memory in amnesic patients with focal hippocampal damage. Proportionate deficits of recall and recognition memory have been observed in some patients with selective hippocampal damage. In addition, these patients showed an impairment of both the recollection and familiarity aspects of recognition memory. In contrast, other amnesic patients with selective hippocampal lesions demonstrated relatively preserved recognition memory, despite severely impaired recall abilities. In some of them, familiarity processes were found to be intact. The resolution of this controversy has important implications for theories of episodic memory. In the present study, we examined the recall and recognition performance of an amnesic patient, MR, who suffered from bilateral hippocampal damage and temporoparietal cortical atrophy following carbon monoxide poisoning. Verbal and nonverbal recall and recognition memory were measured by tasks matched for difficulty. On these tasks, MR’s recall performance was more severely impaired than his recognition memory. In addition, MR’s recognition performance was normal on most of the tasks. In order to determine on which processes MR based his recognition decisions, we administered to the patient and to matched controls the process dissociation procedure. This evaluates the contribution of recollection and familiarity within a recognition task. The results indicated that, in this patient, familiarity was preserved, but recollection was impaired. This study thus supports the idea that amnesic patients with hippocampal damage can show preserved familiarity-based recognition memory, despite poor recall and recollection.