Fractionation of memory in medial temporal lobe amnesia

We report a comprehensive investigation of the anterograde memory functions of two patients with memory impairments (RH and JC). RH had neuroradiological evidence of apparently selective right-sided hippocampal damage and an intact cognitive profile apart from selective memory impairments. JC, had neuroradiological evidence of bilateral hippocampal damage following anoxia due to cardiac arrest. He had anomic and "executive" difficulties in addition to a global amnesia, suggesting atrophy extending beyond hippocampal regions. Their performance is compared with that of a previously reported hippocampal amnesic patient who showed preserved recollection and familiarity for faces in the context of severe verbal and topographical memory impairment [VC; Cipolotti, L., Bird, C., Good, T., Macmanus, D., Rudge, P., & Shallice, T. (2006). Recollection and familiarity in dense hippocampal amnesia: A case study. Neuropsychologia, 44, 489-506.] The patients were administered experimental tests using verbal (words) and two types of non-verbal materials (faces and buildings). Receiver operating characteristic analyses were used to estimate the contribution of recollection and familiarity to recognition performance on the experimental tests. RH had preserved verbal recognition memory. Interestingly, her face recognition memory was also spared, whilst topographical recognition memory was impaired. JC was impaired for all types of verbal and non-verbal materials. In both patients, deficits in recollection were invariably associated with deficits in familiarity. JC's data demonstrate the need for a comprehensive cognitive investigation in patients with apparently selective hippocampal damage following anoxia. The data from RH suggest that the right hippocampus is necessary for recollection and familiarity for topographical materials, whilst the left hippocampus is sufficient to underpin these processes for at least some types of verbal materials. Face recognition memory may be adequately subserved by areas outside of the hippocampus. (c) 2006 Elsevier Ltd. All rights reserved.