Functional optical imaging has helped scientists at The Scripps Research Institute’s Florida campus (Jupiter) make a discovery fundamental to long-term memory.1 While studying the common fruit fly, the researchers identified a change in chemical influx into a specific set of neurons. The influx was absent in 26 different mutants known to impair long-term memory, according to Ron Davis, who led the study. “This logical conclusion is that this increase, which we call a memory trace, is a signature component of long-term memory.”
The trace is an increased influx into a set of neurons in a part of the insect brain known as mushroom bodies, a pair of oversized lobes that have been compared to the hippocampus, a site of memory formation in humans. Increases in calcium influx also occur with learning in other animal models, Davis said, and it seems highly likely a similar correlation exists in humans.
To measure the changes in the Drosophila neurons, Davis and his colleagues used protein sensors that become fluorescent when calcium levels are increased. These observed memory traces occur in parallel with behavioral changes.
1. D.B.G. Akalal et al., J. Neurosci. 31 (15): 5643–5647 (2011).