1) Functional Connectomics: How does the nervous system affect behavior?
Caenorhabditis elegans has an anatomically well-defined nervous system of just 302 neurons, whose synaptic connections have been mapped precisely by serial electron microscopy.
Knowledge of the cellular connections, however, is only one key to understanding how the circuits work, and only limited insight into function can be deduced from the pure connectome. This is because this dataset does not contain information about the ‘sign’ of individual synapses, the transmitters and postsynaptic receptors used, as well as the synaptic weight and dynamic signalling.
Furthermore, neuronal networks of the worm are more complex than was assumed, because of the adoption of different functional states depending on context and/or the presence of certain neuromodulators. Such brain states involve that anatomical synapses are being switched to active or inactive states, such that several different functional connectomes are overlaid on one anatomical, hard-wired network.