Short- and long-term memories require same gene, but in different brain circuits

Conducting experiments on fruit flies, a group of scientists have found that long-term and short-term memories are stored very differently because they depend upon the activity of a gene in different circuits of the brain. Assistant Professor Josh Dubnau, of Cold Spring Harbor Laboratory (CSHL), has ofund that both short- and long-term memories require the same gene, known as rutabaga, of which humans also have a similar version. He and his colleagues say that a rapidly occurring, short-lived trace in a group of neurons that make up a structure called the "gamma" lobe produces a short-term memory, while a slower, long-lived trace in the "alpha-beta" lobe fixes a long-term memory. During the study, the researchers placed flies in a training tube attached to an electric grid, and administered shocks through the grid right after a certain odour was piped into the tube. They observed that the flies with normal rutabaga genes learnt to associate the odour with the shock, and, if given a choice, buzzed away from the grid. On the other hand, the flies that carried a mutated version of rutabaga in their brains lacked both short- and long-term memory, did not learn the association, and failed to avoid the shocks. However, the researchers also found that total memory deficit did not occur when flies carried the mutated version in either the gamma or in the alpha-beta lobes. They said that restoring the normal rutabaga function in the gamma lobe caused the flies to regain short-term memory, but not long-term memory. Similarly, added the researchers, restoring the gene's function in the alpha-beta lobe alone restored long-term memory, but not short-term memory. "This ability to independently restore either short- or long-term memory depending on where rutabaga is expressed supports the idea that there are different anatomical and circuit requirements for different stages of memory," Dubnau said. His team will next try to determine how much cross talk, if any, is required between the two lobes for long-term memory to get consolidated, hoping that it may add to the progress that scientists have already made in treating memory deficits in humans with drugs aimed at molecular members of the rutabaga-signalling pathway to enhance its downstream effects. A research article describing the study has been published in the journal Current Biology.