Sleep : the architect of memory
These results seem to indicate that the hippocampus processed the mnesic traces during that first night. As time passed, it passed the baton to the medial prefrontal cortex which took over the role of the conductor orchestrating the different cortical areas involved, in this case the extrastriate visual areas, where activity could still be observed.
Bruno Bontempi, (University of Bordeaux)and Paul Frankland (University of Toronto) have also published data that show that a lesion of the medial prefrontal cortex in rats does not interfere with the animal's ability to access recent memories but does prevent it from remembering older ones. Pierre Maquet underlines, however, that it is difficult to establish homologies between rats and humans in this regard because the prefrontal cortex is much more developed in humans.
The results of the study conducted at the CRC contribute further to underlining the importance of sleep in memorization phenomena. More specifically, they confirm that sleep improves systemic memory consolidation, i.e. the long- term reorganization of the mnesic trace in the cortical networks.
The influence of emotions
As mentioned above, Pierre Maquet and his team have recently published the results of a second study in PLOS Biology (October 2007). It is known empirically that "emotional" (i.e. emotionally charged) events tend to be remembered more easily than "neutral" ones. This led the Liège researchers to question whether a particular treatment is reserved for consolidation of this type of memory during sleep.