RETRACTED ARTICLE: Neuromodulation of internal emergent representations for sequential tasks

Serotonin and dopamine transmitters are synthesized in the lower brain but are transmitted widely to many areas of the brain for diffused use. Emergent representations are critical for understanding their effects. In prior work Zheng et al. (in: Proceedings of 2013 international joint conference on neural networks (IJCNN2013), pp 1404–1411, Dallas, Texas, USA, August 4–9, 2013), their effects on internal, non-motor neurons were studied for only pattern recognition tasks. In this paper, we study their effects on sequential tasks—robot navigation under different settings. They are sequential tasks because the outcome of behavior depends on not only the current behavior as in pattern recognition but also the previous behaviors and environment (e.g., previous navigational trajectories). Analytically, we show that the serotonin and dopamine systems affect the performance of sequential tasks in a compound way. Experimentally, we show that the effect on the learning rate of internal feature neurons (in the Y area) allows the agent to approach a friend and avoid an enemy faster as compounding effects of sequential states in static and dynamic environment. Further, we test the effect of punishment and reward schedule with the same initial locations. These simulation experiments all indicate that the reinforcement learning via the serotonin and dopamine systems is beneficial for developing desirable behaviors in this set of sequential tasks—staying statistically close to its friend and away from its enemy. As far as we know, this is the first work that investigates the effects of reinforcer (via serotonin and dopamine) on internal neurons (Y neurons) for sequential tasks using emergent representations.