How the brain brings back memories of past events remains largely unknown. In a collaboration between the MRC Cognition & Brain Sciences Unit in Cambridge (Dr. Maria Wimber), the University of Konstanz (Dr. Simon Hanslmayr, Zukunfskolleg) and the Otto-von-Guericke University Magdeburg, researchers have now identified a rapid memory reactivation mechanism that has so far only been speculated about. In this project, participants learned long lists of words while the screen was flickering at different frequencies. Such flickering stimulation is known to induce a frequency-specific "oscillating" brain signal that is clearly visible in the human electroencephalogram (EEG). The study revealed that when participants later remember one of the previously studied words, the brain rapidly reproduces a signal at the particular frequency that had been present during learning. These results indicate that when people recollect past events, the brain transiently returns to the state that it was in when the event had first been encountered. The study is available online in Current Biology:

http://www.cell.com/current-biology/abstract/S0960-9822(12)00646-X

The research results of the joint work of Fellow of the Zukunftskolleg, Simon Hanslmayr with Prof. Mikael Johansson and with Dr. Gerd Waldhauser (University of Lund, Sweden) showed for the first time that retrieval of associated memory contents inhibits interfering contents which leads to the forgetting of the latter. A distinction between the patterns of contents which have to be recalled and of interfering contents was achieved by means of EEG.  This method provides direct evidence for the reactivation and inhibition of the interfering memory contents. The findings were published in the "The Journal of Neuroscience“(February 8, 2012 • 32(6):1953–1961 • 1953) under the title "Alpha/Beta Oscillations Indicate Inhibition of Interfering Visual Memories".

In this article, by means of simultaneous measuring of brainwaves (EEG) and functional magnetic resonance tomography (MRT), it is shown which neuronal synchronization patterns are at the bottom of the formation of new memory contents.

The article from "The Journal of Neuroscience" is available here.