The 2004 film Eternal Sunshine of the Spotless Mind tells the story of a couple who undergo a procedure to erase memories of each other when their relationship turns sour. Now US and Chinese researchers have claimed that they can selectively erase memories from laboratory mice, suggesting that it may one day be possible to erase traumatic memories in people.
The study, which is published in the October 23 issue of the journal Neuron, reveals a mechanism by which both new and old memories can be eliminated without damage to brain cells. Dr Tsien’s group had previously established the role of the NMDA receptor in memory formation. The new study looked at events downstream of the NMDA receptor, and found that over-expression of α-calcium/calmodulin-dependent kinase II (αCaMKII) while a memory was being recalled eliminated that single memory. During memory formation, the NMDA receptor is activated, resulting in the insertion of AMPA receptors into the synapses and subsequent strengthening of synaptic connections. αCaMKII is believed to play an important role in the insertion of AMPA into the synapses during learning and subsequent strengthening of connections between neurons to form a memory. It has previously been very difficult to dissect out the individual components of memory because of the relatively long timescales needed to switch off production of a particular protein. Dr Tsien’s group has now developed a ‘chemical-genetic’ method which means that αCaMKII can be turned on and off instantly in transgenic mice which have been bred to overproduce the molecule. Using this technique, the group were able to selectively erase memories in the mice during the retrieval stage. The team caution that, although the results are very exciting, translation to humans will need much more work.