Identified nerve cells and insect behavior

Studies of insect identified neurons over the past 25 years have provided s ome of the very best data on sensorimotor integration; tracing information flow from sensory to motor networks. General principles have emerged that h ave increased the sophistication with which we now understand both sensory processing and motor control. Two overarching themes have emerged from stud ies of identified sensory interneurons. First, within a species, there are profound differences in neuronal organization associated with both the sex and the social experience of the individual. Second, single neurons exhibit some surprisingly rich examples of computational sophistication in terms o f (a) temporal dynamics (coding superimposed upon circadian and shorter-ter m rhythms), and also (b) what Kenneth Roeder called 'neural parsimony': tha t optimal information can be encoded, and complex acts of sensorimotor coor dination can be mediated, by small ensembles of cells. Insect motor systems have proven to be relatively complex, and so studies of their organization typically have not yielded completely defined circuits as are known from s ome other invertebrates. However, several important findings have emerged. Analysis of neuronal oscillators for rhythmic behavior have delineated a pr ofound influence of sensory feedback on interneuronal circuits: they are no t only modulated by feedback, but may be substantially reconfigured. Additi onally, insect motor circuits provide potent examples of neuronal restructu ring during an organism's lifetime, as well as insights on how circuits hav e been modified across evolutionary time. Several areas where future advanc es seem likely to occur include: molecular genetic analyses, neuroecologica l syntheses, and neuroinformatics - the use of digital resources to organiz e databases with information on identified nerve cells and behavior. (C) 20 01 Elsevier Science Ltd. All rights reserved.