=============== Neuromodulation =============== A neuromodulatory event influences synaptic behaviours by simulating additional neurontransmitters. It is implemented by linking from projection fibers to existing synapses as illustrated below: .. image:: ./img/neuromodulation.png Projection edges (connection type in SONATA: `neuromodulatory`) are created between virtual neurons and existing connectome synapses, as defined by `SONATA docs `_. - A neuromodulator sends a spike, and the relevent post cell receives the spike at synapses e.g. S1, S2 and S7. - The synapse model at S1, S2, and S7 has to manage both presyanaptic spikes (nc_type = 0) and neuromodulatory spikes (nc_type = 10). - Neuromodulatory spikes may change parameters in the synapse models (e.g. `Use`), but not the membrane current `i`. - The neuromodulators influence one or more, but not all synapses from a PRE neuron (e.g. S3 is not changed) - The neuromodulators influence synapses coming from different neurons (e.g. S7 that comes from somewhere else) For each neuromodulatory projection, ``Neurodamus`` finds its closest post cell synapse by the location parameter, the exact `afferent_section_id` and the closest `afferent_section_pos` (< 0.05). Spikes from neuromodulators are injected via `replay `_. The neuromodulatory strength (`neuromodulation_strength`) and decay time (`neuromodulation_dtc`) are pre-defined in projection edges, and users can override them via a simulation config file, see `connection_overrides `_.