“Look into the light”: Scientists Use Light to Manipulate Memories
The Neuralyser device used in the ‘Men in Black’ franchise is the signature tool for erasing specific memories with light. While it was considered as standard issue equipment at MIB headquarters, is this something which can be achieved in real life? Apparently so. Still a far cry from the memory device seen on screen, a team of scientists at the UC Davis Centre for Neuroscience and Department of Psychology have used light to erase specific memories in mice.
Until the recent arrival of Optogenetics, a 40 year old theory by neuroscientists could not be proven. The new technique pioneered by Karl Diesseroth at Stanford University, is used to manipulate and study nerve cells using light, allowing fundamental assumptions in the field to be finally confirmed.
Kazumasa Tanaka, Brian Wiltgen and colleagues at UC Davis applied the technique to test a long-standing idea about memory retrieval, proving the basic theory of how the cerebral cortex and the hippocampus work together to retrieve episodic memories – – memories about specific places and events.
“The theory is that learning involves processing in the cortex, and the hippocampus reproduces this pattern of activity during retrieval, allowing you to re-experience the event,” Wiltgen said. If the hippocampus is damaged, patients can lose decades of memories.
Wiltgen and Tanaka used mice genetically modified so that when nerve cells are activated, they both fluoresce green and express a protein that allows the cells to be switched off by light. They were therefore able both to follow exactly which nerve cells in the cortex and hippocampus were activated in learning and memory retrieval, and switch them off with light directed through a fibre-optic cable.
They trained the mice by placing them in a cage where they got a mild electric shock. Normally, mice placed in a new environment will nose around and explore. But when placed in a cage where they have previously received a shock, they freeze in a “fear response.”
Tanaka and Wiltgen were able to switch off the specific nerve cells in the hippocampus, and show that the mice lost their memories of the unpleasant event.
The arrival of this research opens further advancements for studies in memory management, and the offer of promising possibilities for trauma patients in the future.
Journal Reference: Kazumasa Z. Tanaka, Aleksandr Pevzner, Anahita B. Hamidi, Yuki Nakazawa, Jalina Graham, Brian J. Wiltgen. Cortical Representations Are Reinstated by the Hippocampus during Memory Retrieval. Neuron, 2014 DOI:10.1016/j.neuron.2014.09.037
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