Extent and Neural Basis of Semantic Memory Impairment in Mild Cognitive Impairment

Article type: Research Article

Authors: Barbeau, Emmanuel J.^{a; b; *} | Didic, Mira^{c; d} | Joubert, Sven^{e; f} | Guedj, Eric^g | Koric, Lejla^c | Felician, Olivier^{c; d} | Ranjeva, Jean-Philippe^h | Cozzone, Patrick^h | Ceccaldi, Mathieu^{c; d}

Affiliations: [a] Université de Toulouse, UPS, Centre de Recherche Cerveau et Cognition, Toulouse, France | [b] CNRS, CerCo, Toulouse, France | [c] APHM, CHU Timone, Service de Neurologie et Neuropsychologie, Marseille Cedex, Marseille, France | [d] Aix-Marseille Univ, Laboratoire Epilepsies et Cognition, INSERM, Marseille Cedex, Faculté de Médecine, Marseille, France | [e] Département de psychologie, Université de Montréal, Montréal, Canada | [f] Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montréal, Canada | [g] Service Central de Biophysique et Médecine Nucléaire, CHU Timone and Centre Européen de Recherche en Imagerie Médicale, Université de la Méditerranée, Marseille, France | [h] Centre d'Exploration Métabolique par Résonance Magnétique (UMR CNRS), Universitée de la Méditerranée, Marseille, France

Correspondence: [*] Correspondence to: E.J. Barbeau, Centre de Recherche Cerveau and Cognition (CerCo), CNRS CERCO UMR 5549, Pavillon Baudot, CHU Purpan, BP 25202, 31052 Toulouse Cedex, France. Tel.: +335 81 18 49 56; E-mail: emmanuel.barbeau@cerco.ups-tlse.fr.

Abstract: An increasing number of studies indicate that semantic memory is impaired in mild cognitive impairment (MCI). However, the extent and the neural basis of this impairment remain unknown. The aim of the present study was: 1) to evaluate whether all or only a subset of semantic domains are impaired in MCI patients; and 2) to assess the neural substrate of the semantic impairment in MCI patients using voxel-based analysis of MR grey matter density and SPECT perfusion. 29 predominantly amnestic MCI patients and 29 matched control subjects participated in this study. All subjects underwent a full neuropsychological assessment, along with a battery of five tests evaluating different domains of semantic memory. A semantic memory composite Z-score was established on the basis of this battery and was correlated with MRI grey matter density and SPECT perfusion measures. MCI patients were found to have significantly impaired performance across all semantic tasks, in addition to their anterograde memory deficit. Moreover, no temporal gradient was found for famous faces or famous public events and knowledge for the most remote decades was also impaired. Neuroimaging analyses revealed correlations between semantic knowledge and perirhinal/entorhinal areas as well as the anterior hippocampus. Therefore, the deficits in the realm of semantic memory in patients with MCI is more widespread than previously thought and related to dysfunction of brain areas beyond the limbic-diencephalic system involved in episodic memory. The severity of the semantic impairment may indicate a decline of semantic memory that began many years before the patients first consulted.

Keywords: Long-term memory, mild cognitive impairment, neuroimaging, semantic memory

DOI: 10.3233/JAD-2011-110989

Journal: Journal of Alzheimer's Disease, vol. 28, no. 4, pp. 823-837, 2012