Localization of electroreceptive function in rabbits

The detection process by which animals react to the presence of electromagnetic fields (EMFs) may be a form of sensory transduction. However, the anatomic location of signal transduction in most species is unknown. Attempts to solve this problem by applying local EMFs and registering the resulting changes in the electroencephalogram (EEG) have not succeeded because of the nonstationarity of the EEG and the insensitivity of linear methods of analysis. We approached the problem of localizing electroreception in rabbits by using recurrence quantification analysis (RQA), a novel method of nonlinear analysis designed to detect small deterministic changes in a larger signal irrespective of considerations involving stationarity. When 2.5 G, 60 Hz was applied to the entire body, increased determinism in the EEG was found in all 10 animals studied, as evidenced by statistically significant increases in two RQA quantifiers. A similar result occurred when the field was applied only to the front half of each animal, but no effect on the EEG was seen when the field was applied only to the back half. When the field was localized to the head, the effect on the determinism in the EEG was again seen. When the field was further localized to the eye, the effect did not occur. Overall, the results indicated that detection of the field occurred in cells or extracellular structures in the head, probably the brain, although the methods used did not have the resolution to discriminate between specific brain structures. Thus, our results showed that the presence of transient deterministic brain states induced by an EMF signal could be documented using dynamical analysis, thereby allowing us to infer the approximate anatomic location of the signal's transduction.