To understand memory function, olfactory memory in insect is studied for many years. Flies begin to avoid the odor experienced with electric shock (punishment) and begin to be attracted to the odor experienced with sucrose (reward). To complete the olfactory memories, olfactory information and reward/punishment information are converged and output changed. The pathways conveying olfactory information are well studied and reward/punishment are partially studied, but the whole memory pathways are not fully understood. To investigate novel memory pathways, we developed a CREB reporter system.
In Drosophila melanogaster, it is known that CREB is involved in memory formation. Specifically, CREB activity in the Mushroom body (MB) and other few neurons are thought to be important for memory. In the CREB reporter flies, many CREB reporter positive neurons were broadly observed in addition to the MB. Here, we used CREB reporter to screen novel neurons involved in memory. Employing Gal4/UAS system, the reporter allows us to control neurons in which CREB is activated. Inhibition of the output from the reporter positive neurons by Shibirets revealed that CREB reporter positive neurons (excluding the MB) are involved in both olfactory aversive memory and appetitive memory but in different ways. By using a Gal4 inhibitor Gal80, a subset of CREB reporter positive neurons are revealed to be needed to the memories. These results suggest a small subset of CREB reporter positive neurons have pivotal roles in the olfactory memory.