Responses of central neurons to electrical and magnetic stimuli of the ampullae of lorenzini in the Black Sea skate

1. Evoked and neuronal responses in the area acustico-lateralis to electrical and magnetic stimulation of ampullae of Lorenzini were studied in the anaesthetised Black Sea skate,Trygon pastinaca. 2. Evoked responses with marked negative phase corresponded to the excitation of neurons, those with marked positive phase to the inhibition of neurons (Fig. 2). 3. 80% of all studied neurons were spontaneously active (8.2±1.0 imp/sec). The background activity of some neurons was modulated in the rhythm of the respiratory movements. 4. Thresholds for electrical stimulation were in the range of 1×10−10−6× 10−9 A/mm2. 5. The character of neuronal responses depended on the stimulus polarity (Figs. 2, 3). 6. Relations between the parameters of stimulation and the latencies of “on” -and “off”-responses, the spike frequency, the duration of “contrast interval” as well as the thresholds of reactions were analysed (Figs. 4, 5, 7). 7. Four main patterns of responses to electrical stimulation were observed: phasic-tonic, tonic, sustained and bursting (Fig. 6). 8. Neurons responded to a changing magnetic field penetrating the fish. The character of the responses depended on the direction of the magnetic field, and the intensity depended on the rate of magnetic field change. A constant magnetic field failed to influence single unit activity (Figs. 8–11). 9. The threshold for magnetic stimulation was 2 Gs/sec. Thus perception of the magnetic field of the earth by the fish is possible.