Abstract
Relational memory theory holds that the hippocampus supports, and amnesia following hippocampal damage impairs, memory for all manner of relations. Unfortunately, many studies of hippocampal-dependent memory have either examined only a single type of relational memory or conflated multiple kinds of relations. The experiments reported here employed a procedure in which each of several kinds of relational memory (spatial, associative, and sequential) could be tested separately using the same materials. In Experiment 1, performance of amnesic patients with medial temporal lobe (MTL) damage was assessed on memory for the three types of relations as well as for items. Compared to the performance of matched comparison participants, amnesic patients were impaired on all three relational tasks. But for those patients whose MTL damage was limited to the hippocampus, performance was relatively preserved on item memory as compared to relational memory, although still lower than that of comparison participants. In Experiment 2, study exposure was reduced for comparison participants, matching their item memory to the amnesic patients in Experiment 1. Relational memory performance of comparison subjects was well above amnesic patient levels, showing the disproportionate dependence of all three relational memory performances on the integrity of the hippocampus. Correlational analyses of the various task performances of comparison participants and of college-age participants showed that our measures of item memory were not influenced significantly by memory for associations among the items.
Highlights
The critical participation of the medial temporal lobe (MTL), and especially the hippocampus, in memory has been well established since the earliest reports of profound amnesia following MTL resection in the patient H.M. (Scoville and Milner, 1957)
We considered whether the finding from Experiment 1 that item memory performance, while relatively preserved compared to relational memory in hippocampal amnesia but inferior to that of the comparison participants, had been influenced in any way by memory for associative relations
The goals of the present work were (1) to develop a paradigm capable of testing memory for different types of relations independently, and of testing item memory, all based on the same study trials with the same stimulus materials, and (2) using this paradigm to assess the status of these different aspects of relational and item memory in hippocampal amnesia
Summary
The critical participation of the medial temporal lobe (MTL), and especially the hippocampus, in memory has been well established since the earliest reports of profound amnesia following MTL resection in the patient H.M. (Scoville and Milner, 1957). The critical participation of the medial temporal lobe (MTL), and especially the hippocampus, in memory has been well established since the earliest reports of profound amnesia following MTL resection in the patient H.M. Work with neurological patients with MTL damage has documented many examples of spatial memory impairments, including deficits in memory for arbitrary object locations (Crane and Milner, 2005; Holdstock et al, 2002, 2005), spatial arrangements among items in scenes (Hannula et al, 2006, submitted; Ryan et al, 2000), spatial lay-outs of residences occupied for years following the onset of amnesia (Bayley and Squire, 2005), and spatial navigation of complex large-scale places (Maguire et al, 2006)
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