By Konrad Heinz
September’s neuron of the month is a B’2a PAM DAN – it is a dopaminergic neuron of the mushroom body. The mushroom body (MB, shown in pink) is a major site of olfactory learning in the fly brain, and dopaminergic neurons (DANs), which release the widely conserved neurotransmitter dopamine, are understood to provide learning signals, both in fruit flies and in other species, including humans. Dopamine release can mediate both “reward” and “punishment” signals, contributing to the formation of memories which result in the fly approaching odours it has experienced in a positive context and avoiding odours it has experienced in a negative context. The PAM class of DANs, which this neuron belongs to, is thought to signal reward rather than punishment. Dopamine release by DANs modifies synapses between odour-coding Kenyon cells (which make up the MB) and MB output neurons which instruct behaviour. In this way DANs can “write memories”, as the influence an odour has on behaviour is changed as a result of changing the synaptic connections between neurons processing odour input and behavioural output. We are reconstructing dopaminergic neurons, as well as their upstream neurons, to better understand how they process information to change memory.