Josh Dubnau kicked off the 'redundancy session' with a very spirited talk presenting a systemic view of multiple memory systems in multiple neural populations of classical olfactory conditioning in Drosophila. After a wonderful introduction about the complexities of learning and memory in flies, he emphasized how important a so far unexplored rutabaga-independent learning mechanism is. Then he showed how the sufficiency of different mushroom-body subpopulations for memory shifts between the different memory phases. He then went upstream of the rut-adenylyl cyclase, to the dopamine receptors (he studies aversive learning). Restoring the relevant dopamine D2 receptor in gamma lobe neurons is sufficient to fully restore memory performance. This result suggests that the initial memory in the gamma lobes needs to be transfered from the gamma lobes to the alpha/beta lobes, as rut is required in these neurons for long term memory, but apparently, the D2 receptor is not.

Next up was Lesli Griffith talking about "Sensory cue redundancy in courtship learning: Many ways to learn the same lesson". In order to make an adaptive decision of whether or not court a female, males have a number of different sensory cues at their disposal to make an informed decision. This decision is plastic and can be modulated by prior experience, e.g. courtship conditioning.Courtship conditioning happens when naive males encounter a mated females. Mated females do not want to mate a second time, meaning that all courtship efforts by the male are rejected by the female. This rejection serves as negative feedback ('positive punishment' in operant terms) and the animals learn the odor of the mated female (which is different from that of a virgin female) and selectively suppress courtship to mated females in the future. Interestingly, this memory generalizes to other tester animal to some degree, such that courtship in general is reduced. She then showed a number of elegant experiments showing that the rejection of copulation actually constitutes the punishing stimulus mediating the learning. The smell of the animals used to condition the male was the crucial factor for the amount of courtship in the test after training. Thus, depending on how the male has experienced the rejection (i.e., for how long and by what animal), it will learn to suppress its courtship more or less specifically to all conspecifics or just the particular type it was conditioned with.

Brian Smith concluded the redundancy session with a presentation on multiple memory representations in honey bees. Brian showed a series of experiments using odor preexposure and olfactory conditioning of odor mictures in conjunction with imaging of the antennal lobe. He showed several sites of plasticity in the antennal lobe. this plasticity poses the problem that the signal from the antennal lobe that is transmitted to the mushroom-bodies changes after training. If the memory is also stored in the mushrom-bodies, how do they recognize the changing signal from the antennal lobe? Brian could not answer this question but went on to present some data on the output from the mushroom-body by recording electrophysiologically from the extrinsic neurons. Surprisingly, they found that these extrinsic neurons can distinguish between odor much more quickly than the projections neurons, even though the Projection neurons are upstream in the information flow. Computational models suggest that it is the divergence from projection neurons to mushroom-body neurons that helps speed up the identification of odors at the output of the mushroom-bodies.