[Frequency-threshold characteristics of the subcortical formations of the auditory analyzer of the dolphin Phocaena phocaena]

The evoked potentials (EP) have been recorded in subcortical auditory structures of porpoises exposed to ultrasound stimulation. The magnitude of EP thresholds served as the criterion of auditory centers sensitivity to variations in stimulus frequency. The region of maximum sensitivity occurred within the range 100 to 120 kHz and in some trials additional maximum was observed. Reaction thresholds of "off"-responses invariably exceeded those of "on"-responses. Frequency-threshold curves for both reaction types coincided.