We observed seven brain structures showing the highest activation with increasing load of the retrieved images, viz. The participants had to retrieve these previously memorized images during the fMRI scan in 15 s, with their eyes closed. Behavioral assessments on a separate group of participants (#22) provided the average loads of the images. The images were of 12 categories relevant to daily events, with each category including a high and a low load image. We asked 32 healthy young volunteers to memorize all possible details of 24 images over a 12-day period ending 2 days before the fMRI scan. Despite numerous studies about the effect of cognitive loads on working memory processes, whether these can be applied to long-term memory processes is unclear. Identifying the brain structures which manage this increasing cognitive demand would enhance our knowledge of human memory.
One of the less well-understood aspects of memory function is the mechanism by which the brain responds to an increasing load of memory, either during encoding or retrieval.