Episodic memory enables us to consciously recollect personally experienced past events. Memory performance is reduced in patients with mild cognitive impairment (MCI) – an at risk condition for Alzheimer’s disease (AD). We used functional magnetic resonance imaging (fMRI) to compare brain activity during memory encoding in 29 healthy, elderly subjects (mean age 67.7 years, SD 5.4 years) and 21 MCI patients (mean age 69.7 years, SD 7.0 years). Subjects remembered a list of words while fMRI data was acquired. Later, they had to recognize these words among a list of distractor words. The use of an event-related paradigm made it possible to selectively analyze successfully encoded items in each individual. We compared activation for successfully encoded words between healthy elderly subjects and MCI patients. The main intergroup difference was found in left hippocampus and surrounding medial temporal lobe (MTL) regions for the MCI patients as compared to healthy subjects during successful encoding. These results suggest that in MCI patients an increase of MTL activation is necessary for successful memory encoding. Hippocampal activation may help to link newly learned information to items already stored in memory. Increased activation in MTL regions in MCI may reflect a compensatory response to beginning AD pathology.
- episodic memory
- mild cognitive impairment