Electrosensory activity in the telencephalon of the axolotl

Electrical shock of the anterior lateral line nerve evokes slow wave potentials in the contralateral corpus striatum and bilaterally in the medial pallium of the telencephalon of axolotls. The onset latency of the evoked response in the medial pallium (70 ms) is considerably longer than that of the corpus striatum (46 ms). Quasi-natural stimuli, such as weak uniform electric fields (100 microV/cm) or water drops striking the surface of the water surrounding the axolotls elicited evoked potentials or multiple unit activity in the corpus striatum but not in the medial pallium. Striatal responses to weak electric fields have a threshold of approximately 50 microV/cm and habituate at rates higher than 1 every 10 s. Multiple-unit responses in the medial pallium were elicited only by gentle strokes to the snout with a brush, and it is possible that trigeminal fibers were inadvertently stimulated in the nerve shock cases. The discovery that the corpus striatum is a major telencephalic target of electrosensory information rather than the medial pallium as reported in elasmobranch fishes, suggests that there are additional electrosensory telencephalic centers in elasmobranchs and/or that homologous nuclei of the midbrain or thalamus have evolved different projections.