Hippocampal Morphology and Autobiographic Memory in Mild Cognitive Impairment and Alzheimer’s Disease

Philipp A. Thomann, Ulrich Seidl, Julia Brinkmann, Dusan Hirjak, Tanja Traeger, R. Christian Wolf, Marco Essig, Johannes Schrode

Abstract

Autobiographical memory (AM) comprises memories of one’s own past that are characterized by a sense of subjective time and autonoetic awareness. AM deficits are among the major complaints of patients with Alzheimer’s disease (AD) even in early or preclinical stages. However, little is known on the association between cerebral alterations and AM in mild cognitive impairment (MCI) and AD. In the current study, patients with AD or MCI and healthy controls underwent high-resolution magnetic resonance imaging (MRI) and neuropsychological testing including semi-structured assessment of semantic and episodic AM of distinct lifetime periods. In MRI analysis, FSL-FIRST was used to automatically ascertain volume and shape of the hippocampal formation. Episodic, but not semantic AM loss was associated with morphological changes of the hippocampus, primarily involving the left hemisphere. According to shape analyses, these associations referred to regionally specific rather than global atrophy of the hippocampus. Our study demonstrates that loss of episodic AM early in the course of AD is associated with regionally confined hippocampal atrophy, thus supporting the multiple trace theory for the role of the hippocampus in episodic AM. Our findings are not only relevant for the understanding of memory function, but may also contribute to facilitating the early diagnosis of AD.

Keywords: Alzheimer’s disease, Autobiographical memory, Hippocampus, Magnetic resonance imaging, Mild cognitive impairment, hippocampal degeneration

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