A team of researchers headed by Nikolai Axmacher performed a memory test on a series of persons while monitoring their brain activity by functional magnetic resonance imaging (fMRI). The experimental setup comprised several resting states including a nap inside a neuroimaging scanner.
Depending on one's mood and activity different regions are active in the human brain. Perceptions and thoughts also influence this condition and this results in a pattern of neuronal activity which is linked to the experienced situation. When it is recalled, similar patterns, which are slumbering in the brain, are reactivated.
The prevalent theory of memory formation assumes that memories are stored in a gradual manner. At first, the brain stores new information only temporarily. For memories to remain in the long term, a further step is required known as "consolidation".
Axmacher, researcher at the Department of Epileptology of the University of Bonn, said visual and spatial perceptions have to be linked together. Such tasks involve several brain regions. These include the visual cortex and the hippocampus, which takes part in many memory processes.
Axmacher said the analysis showed that neuronal activity associated with images that were shown during the experiment initially did reappear during subsequent resting periods and in the sleeping phase.
"The more frequently a pattern had reappeared, the more accurate test participants could label the corresponding image", Axmacher summarizes the findings. "These results support our assumption that neural patterns can spontaneously reappear and that they promote the formation of long-lasting memory contents. Our experiment shows that this phenomenon also happens in humans."
The study indicated that resting periods can generally foster memory performance. Night sleep is considered to be beneficial for the consolidation of memory contents. But it usually takes many hours and includes multiple transitions between different stages of sleep.
The study was published in the journal of Neuroscience.