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Open Access Research article

Medial temporal lobe function during emotional memory in early Alzheimer’s disease, mild cognitive impairment and healthy ageing: an fMRI study

Mario A Parra1*, Vivek Pattan2, Dichelle Wong3, Anna Beaglehole4, Jane Lonie3, Hong I Wan5, Garry Honey5, Jeremy Hall3, Heather C Whalley3 and Stephen M Lawrie3

Author Affiliations

1 Scottish Dementia Clinical Research Network, Human Cognitive Neuroscience and Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh EH8 9JZ, UK

2 Higher Specialty Trainee -Old Age Psychiatry, Stobhill Hospital, Glasgow, UK

3 Division of Psychiatry, School of Molecular Medicine, Royal Edinburgh Hospital, Morningside, University of Edinburgh, Edinburgh, EH10 5HF, UK

4 Old Age Psychiatry, St John’s Hospital, West Lothian, UK

5 Translational Medicine, BioTherapeutics Clinical Programs, Pfizer, Inc, Cambridge, USA

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BMC Psychiatry 2013, 13:76  doi:10.1186/1471-244X-13-76

Published: 6 March 2013

Abstract

Background

Relative to intentional memory encoding, which quickly declines in Mild Cognitive Impairment (MCI) and Alzheimer’s disease (AD), incidental memory for emotional stimuli appears to deteriorate more slowly. We hypothesised that tests of incidental emotional memory may inform on different aspects of cognitive decline in MCI and AD.

Methods

Patients with MCI, AD and Healthy Controls (HC) were asked to attend to emotional pictures (i.e., positive and neutral) sequentially presented during an fMRI session. Attention was monitored behaviourally. A surprise post-scan recognition test was then administered.

Results

The groups remained attentive within the scanner. The post-scan recognition pattern was in the form of (HC = MCI) > AD, with only the former group showing a clear benefit from emotional pictures. fMRI analysis of incidental encoding demonstrated clusters of activation in para-hippocampal regions and in the hippocampus in HC and MCI patients but not in AD patients. The pattern of activation observed in MCI patients tended to be greater than that found in HC.

Conclusions

The results suggest that incidental emotional memory might offer a suitable platform to investigate, using behavioural and fMRI measures, subtle changes in the process of developing AD. These changes seem to differ from those found using standard episodic memory tests. The underpinnings of such differences and the potential clinical use of this methodology are discussed in depth.

Keywords:
Alzheimer’s disease; Mild cognitive impairment; fMRI; Medial temporal lobe; Incidental memory; Emotional memory