What can flies teach us about long-term memory?
Whilst memories are fluid at first, they can be consolidated into stable long-term memory. But what is the mechanism behind memory consolidation in animals?
A team led by Takaomi Saka from Tokyo Metropolitan University (Japan), have pinpointed the Apterous (Ap) protein as a key part of the memory consolidation mechanism in the Drosophila fruit fly. These results help to unravel the complex biochemistry of memory.
However, for some time scientists have been puzzled by the fact that Ap is still active after the flies have matured physically.
To find out more, Saka and colleagues studied the flies’ brains. Ap was found in the mushroom bodies, a pair of structures in the brain involved in learning and memory, where it forms a complex with a cofactor called Chi. This Ap/Chi complex acts as a transcription factor that helps to maintain long-term memories.
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They also observed Ap in the clock neurons, which play a role in behavioral arousal and sleep, by comparing flies with the Ap mutation to wild type flies. They found that Ap helps to regulate the response of GABA receptors to the inhibitory neurotransmitter GABA in the clock neurons. A suitable level of activity from GABA receptors led to the excitement of the large ventral-lateral clock neurons, which in turn assisted in memory consolidation.
When tested, the team found that, the effect of insufficient Ap in mutated fruit flies was mitigated by artificially suppressing the expression of GABA receptors. This confirmed their proposed mechanism for the role of AP in memory consolidation.
These findings reveal that Ap plays two vital roles in long-term memory: binding with Chi cofactors to maintain memories and regulating neurotransmitters to consolidate long-term memories. In addition, this study confirmed that adult Ap mutants have problems with retaining memories relating to past events.
Notably, the biochemistry uncovered in this study has the potential to give insights into mammalian memory, as mammals have proteins with similar functions to Ap in fruit flies. The team anticipate that their results could lead to new approaches to the treatment of memory disorders.
