Neuromodulation of Reactive Sensorimotor Mappings as a Short-Term Memory Mechanism in Delayed Response Tasks

This article addresses the relation between memory, representation, and adaptive behavior. More specifically, it demonstrates and discusses the use of synaptic plasticity, realized through neuromodulation of sensorimotor mappings, as a short-term memory mechanism in delayed response tasks. A number of experiments with extended sequential cascaded networks, that is, higher-order recurrent neural nets, controlling simple robotic agents in six different delayed response tasks are presented. The focus of the analysis is on how short-term memory is realized in such control networks through the dynamic modulation of sensorimotor mappings (rather than through feedback of neuronal activation, as in conventional recurrent nets), and how these internal dynamics interact with environmental/behavioral dynamics. In particular, it is demonstrated in the analysis of the last experimental scenario how this type of network can make very selective use of feedback/memory, while as far as possible limiting itself to the use of reactive sensorimotor mechanisms and occasional switches between them.