The Devil sat behind me on the plane the night before last. I tried blogging from SFN last year. It is a silly idea. I will SFN blog after the fact from now on. One of the most remarkable posters I saw this week was from the Ledoux lab. The amygdala is one of the clearest cases for showing a particular memory trace in a structure (conditioned fear). The poster examined a protein marker for activation/plasticity one hour after training in either paired or unpaired tone-fear conditioning. This means that the animals all received the same amount of all stimuli, but the paired group received the tone just prior to shock which is the condition necessary to produce an association.They used a statistical technique called stereotypy to look for patterns of neuronal activation in the amygdala. There were more marked neurons in paired vs unpaired animals, but the more remarkable thing is that it appears to be the same neurons across animals (for 6 animals). Meaning that there may be a neuron that we can name (P1 or P2 were names they were using) whose hardwired function is to handle association between that particular tone and shock. Yes, I realize that this is probably not what it is "hardwired" to do, but you get the point. Part of the case for calling these the same neurons is that P1 (and others) has the same orientation, dendrite outgrowth, and position across animals. They are currently doing electrophysiology to strengthen the case. There are a subset of neurons that are activated with pairing, but not with unpaired conditioning that are being referred to as AANs (Associatively Activated Neurons? I think that's right.) As far as I could see there wasn't any particular anatomical locus you could stuff them in. They looked sort of like Cassiopeia if I remember correctly.