An fMRI study of long-term everyday memory using SenseCam

Abstract

We used a novel automatic camera, SenseCam, to investigate recognition memory for real-life events at a 5-month retention interval. Using fMRI we assessed recollection and familiarity memory using the remember/know procedure. Recollection evoked no medial temporal lobe (MTL) activation compared to familiarity and new responses. Instead, recollection activated diverse regions in neocortex including medial prefrontal cortex. We observed decreased activation in anterior hippocampus/ anterior parahippocampal gyrus (aPHG) at 5 months compared to a 36-hour retention interval. Familiarity was associated with greater activation in aPHG and posterior parahippocampal gyrus (pPHG) than recollection and new responses. Familiarity activation decreased over time in anterior hippocampus/aPHG and posterior hippocampus/pPHG. The engagement of neocortical regions such as medial prefrontal cortex at a 5-month delay, together with the reduced MTL activation at 5 months relative to at 36 hours is in line with the assumptions of Consolidation theory. SenseCam provides a valuable technique for assessing the processes that underlie remote everyday recognition memory.

Keywords:

• fMRI
• Recognition memory
• SenseCam
• Recollection
• Familiarity
• Consolidation

ACKNOWLEDGEMENTS

This research was supported by grants from the Great Western Research Initiative and Microsoft Research.

Notes

¹The “new” images are not in the strictest sense new but were also encountered (for 4000 ms) in the 36-hour retrieval session. We used the same stimuli in both sessions to ensure that differences between old and new stimuli were unlikely to be the result of exposure in the initial session rather than the personal experiencing of the event itself. The crucial difference between old and new stimuli is therefore the personal experience with the old stimuli but not with the new stimuli. We used the term “new” to make instructions to participants consistent across sessions; however, we accept that “lure” may be a more adequate description for the foils.