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. 2004 Sep 9;431(7005):188-91.
doi: 10.1038/nature02853.

Recollection-like memory retrieval in rats is dependent on the hippocampus

Norbert J Fortin  1 , Sean P Wright, Howard Eichenbaum
Affiliations

Recollection-like memory retrieval in rats is dependent on the hippocampus

Norbert J Fortin et al. Nature. .

Abstract

Recognition memory may be supported by two independent types of retrieval, conscious recollection of a specific experience and a sense of familiarity gained from previous exposure to particular stimuli. In humans, signal detection techniques have been used to distinguish recollection and familiarity, respectively, in asymmetrical and curvilinear components of their receiver operating characteristic (ROC) curves, standard curves that represent item recognition across different levels of confidence or bias. To determine whether animals also employ multiple processes in recognition memory and to explore the anatomical basis of this distinction, we adapted these techniques to examine odour recognition memory in rats. Their ROC curve had asymmetrical and curvilinear components, indicating the existence of both recollection and familiarity in rats. Furthermore, following selective damage to the hippocampus the ROC curve became entirely symmetrical and remained curvilinear, supporting the view that the hippocampus specifically mediates the capacity for recollection.

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Conflict of interest statement

Competing interests statement The authors declare that they have no competing financial interests.

Figures

Figure 1
Figure 1
ROCs for recognition performance in humans and rats. a–c, Performance of humans in verbal recognition (adapted from ref. 20). d–f, Performance of rats in odour recognition. d, Normal rats tested with a 30-min delay. Insets: recollection (R) and familiarity (F) estimates. e, Postoperative performance with a 30-min delay, including an estimated curve for controls based on familiarity alone (con F). f, Control rats tested with a 75-min memory delay. Diagonal dotted lines represent chance performance across criterion levels. C, control group; H, hippocampal group. Error bars, ±s.e.m.; asterisk, P < 0.05.
Figure 2
Figure 2
Lesions of the hippocampus reconstructed on coronal sections of the rat brain. Numbers indicate anterior–posterior (AP) distances (in mm) from bregma. Dark grey, smallest lesion; light grey, largest lesion.
Figure 3
Figure 3
Odour recognition task. a, Sequence of odour presentations. b, Test cup heights and reward pay-offs for each bias level.
See this image and copyright information in PMC

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