Noise cancellation in the electrosensory system of the thornback ray; common mode rejection of input produced by the animal's own ventilatory movement

Summary1.The use of electroreception in feeding depends on the detection of the weak fields of the prey above the interference produced by the predator's own bioelectric fields.2.In this study, the ray's ventilatory movements are shown to produce powerful modulation of electroreceptive afferent input.3.The afferent discharge pattern results mainly from changes of the electric fields within the animal, since it is similar in afferents which innervate ampullary canals of opposite orientation.4.If inputs from canals of opposite orientation are subtracted by the CNS, the sensitivity to external fields is enhanced, and the ventilatory interference removed by common mode rejection.5.Recordings from secondary electrosensory neurons provide evidence that the appropriate inputs exist for common mode rejection, and that ventilation related activity is greatly reduced in these cells and virtually absent in recordings from a mesencephalic electrosensory area.