The computational leech

The local bending reflex of the leech computes a well-defined sensorimotor input—output function in which each of several unique patterns of sensory input elicits a unique pattern of motoneuron activity. Interneurons in the reflex respond to most input patterns and contribute to most motor patterns, suggesting a distributed processing mechanism for the reflex. This suggestion is supported by models in which connection strengths are adjusted by a neural network optimization algorithm to reproduce the local bending input—output function. In addition, computational parallels between the local bending network and the perceptron, a major class of artificial neural networks, brings the functional role of local bending interneurons into question and suggests new physiological experiments.