Effect of Signal Orientation on the Firing of Electrosensory Cells in the Electric Fish Eigenmannia

Animals respond to only a relatively small fraction of stimuli in the environment. A recurring question facing investigators of sensory processing is how the nervous system filters and processes information to recognize behaviorally relevant stimuli. An attractive working hypothesis is that systems are hardwired in such a way that a particular unit or class of units responds when the animal encounters the appropriate stimulus or combination of stimuli for a particular behavior. Recent studies have supported an alternate hypothesis, based upon quite different design criteria. Rather than discrete feature detectors tuned to, for instance, the fundamental frequency of a mating call, investigators have found populations of cells with a wide range of tunings but with a preponderance of cells firing in response to a particular range of the behaviorally relevant variable (R.R. Capranica, this volume).