Modeling the effects of neuromodulation on internal brain areas: Serotonin and dopamine

The effects of neuromodulator, such as serotonin and dopamine, on individual neurons in the brain have been known qualitatively. However, it is challenging to computationally model such effects in an emergent network, as the elements of internal representations do not have a static, task-specific meaning. Weng and coworkers modeled the effects of serotonin and dopamine on only motor neurons in emergent networks. In this work, we extend the effects of serotonin and dopamine to all neurons inside the emergent network. Our new theory is that although serotonin and dopamine indicate events of different natures (aversive and appetitive), they produce similar effects on internal non-motor neurons in that they increase their learning rates from the cases without serotonin and dopamine. This is because the presence of serotonin and dopamine indicates a higher importance of the event compared with baseline cases. Experimentally, we show that the enhanced developmental network learns faster under a limited resource.