Elsevier

Neuropsychologia

Volume 47, Issue 11, September 2009, Pages 2181-2187
Neuropsychologia

Amnesia as an impairment of detail generation and binding: Evidence from personal, fictional, and semantic narratives in K.C.

https://doi.org/10.1016/j.neuropsychologia.2008.11.028Get rights and content

Abstract

Autobiographical episodic recall involves active simultaneous generation and binding of various elements that were present during the initial experience. Deficits in this reconstructive process may account for some aspects of retrograde amnesia (RA) for personally experienced events. Constructive and reconstructive processes may involve similar mechanisms. If so, patients with extensive anterograde amnesia (AA) and RA should show deficits in non-recollective cognitive domains, such as imagining events that had never been experienced and recounting non-personal narratives, that presumably rely on constructive and re-constructive processes, respectively. To test these possibilities, patient K.C., who has severe AA and RA for personal episodes, was asked to generate fictional events and to recall and recognize details of well-known fairy tales and bible stories. K.C.’s performance on both tasks was better than expected given his severely impaired autobiographical episodic memory (AM), but significantly worse than that of control participants. K.C. was able to create a skeletal outline for both types of narratives, providing sufficient information to convey their gist, but the narratives were fragmented and lacking in detail. This deficit cannot be explained as resulting entirely from deficient stored semantic knowledge, because K.C. was able to discriminate between true and false details of non-personal semantic narratives on a recognition test, which he cannot do for personal events [Gilboa, A., Winocur, G., Rosenbaum, R.S., Poreh, A., Gao, F., Black, S.E., Westmacott, R., & Moscovitch, M. (2006a). Hippocampal contributions to recollection in retrograde and anterograde amnesia. Hippocampus, 16, 966–980]. Thus, retrograde AM impairment may be viewed as both a loss of information as well as a deficit in reconstructive processes that hamper or prevent the binding of information to generate a cohesive, detail-rich memory.

Section snippets

Participants

K.C. was 52 years old at the time of testing. He is right-handed with 15 years of formal education and suffered irreversible amnesia as a consequence of a traumatic brain injury from a motorcycle accident in 1981. Magnetic resonance imaging (MRI) performed in 1996 revealed a pattern of diffuse brain damage that includes almost complete loss of hippocampal tissue and clear signs of atrophy to the parahippocampus in both hemispheres (see Rosenbaum et al., 2005). Also of note is a large lesion in

Discussion

This study addressed whether extensive remote memory loss specific to autobiographical information in amnesia is due to an inability to represent episodic details in long-term AM or to a more general construction deficit that does not permit generation or binding of details, independent of AM. K.C. had the most difficulty in reconstructing memories of events he experienced in the past, but he also was impaired in constructing from imagination detailed events that were never personally

Acknowledgments

This work was supported by a Natural Sciences and Engineering Research Council grant to R.S.R. (grant no. 312639), FP6 Marie-Curie IRG grant (EU) to A.G., Canadian Institute of Health Research (CIHR) grant to M.M. and G.W. (grant no. MGP-6694), and National Institutes of Mental Health grant to B.L. (grant no. RO1 MIH0076067-02). R.S.R. is supported by a CIHR New Investigator Award. We wish to thank Namita Kumar, Allison Mackey, and Alina Nikiforov for technical assistance, and Raymond Mar and

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