Activation and Effective Connectivity Changes Following Explicit-Memory Training for Face–Name Pairs in Patients With Mild Cognitive Impairment: A Pilot Study

• Authors: Benjamin Hampstead, Emory University; Anthony Stringer, Emory University; Randall F. Stilla, Emory University; Gopikrishna Deshpande, Emory University; Xiaoping P Hu, Emory University; Anna Bacon Moore, Emory University; Krish Sathian, Emory University
• Journal Title: Neurorehabilitation & Neural Repair
• Volume: Volume 25, Number 3
• Publisher: SAGE Publications (UK and US) | 2011, Pages 210-222
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1177/1545968310382424
• Subjects: Biology, Neuroscience; Health Sciences, Rehabilitation and Therapy
• Keywords: cognitive rehabilitation; mnemonic strategy; Alzheimer’s disease; aging; functional magnetic resonance imaging (fMRI); Granger causality analysis

Abstract

Background: Mild cognitive impairment (MCI) is often a precursor to Alzheimer’s disease. Little research has examined the efficacy of cognitive rehabilitation in patients with MCI, and the relevant neural mechanisms have not been explored. We previously reported on a pilot study showing the behavioral efficacy of cognitive rehabilitation using mnemonic strategies for face-name associations in patients with MCI. Here we used functional magnetic resonance imaging (fMRI) to test whether there were training-specific changes in activation and connectivity within memory-related areas. Methods: Six patients with amnestic, multi-domain MCI underwent pre- and post-training fMRI scans, during which they encoded 90 novel face-name pairs, and completed a 4-choice recognition memory test immediately after scanning. Patients were taught mnemonic strategies for half the face-name pairs during three intervening training sessions. Results: Training-specific effects comprised significantly increased activation within a widespread cerebral cortical network involving medial frontal, parietal, and occipital regions, the left frontal operculum and angular gyrus, and regions in left lateral temporal cortex. Increased activation common to trained and untrained stimuli was found in a separate network involving inferior frontal, lateral parietal and occipital cortical regions. Effective connectivity analysis using multivariate, correlation-purged Granger causality analysis revealed generally increased connectivity after training, particularly involving the middle temporal gyrus and foci in the occipital cortex and the precuneus. Conclusion: Our findings suggest that the effectiveness of explicit memory training in patients with MCI is associated with training-specific increases in activation and connectivity in a distributed neural system that includes areas involved in explicit memory.