Invariance of evoked-potential echo-responses to target strength and distance in an echolocating false killer whale.
Brain auditory evoked potentials (AEPs) were recorded in a false killer whale Pseudorca crassidens trained to accept suction-cup EEG electrodes and to detect targets by echolocation. AEP collection was triggered by echolocation pulses transmitted by the animal. The target strength varied from -22 to -40 dB; the distance varied from 1.5 to 6 m. All the records contained two AEP sets: the first one of a constant latency (transmission-related AEP) and a second one with a delay proportional to the distance (echo-related AEP). The amplitude of echo-related AEPs was almost independent of both target strength and distance, though combined variation of these two parameters resulted in echo intensity variation within a range of 42 dB. The amplitude of transmission-related AEPs was independent of distance but dependent on target strength: the less the target strength, the higher the amplitude. Recording of transmitted pulses has not shown their intensity dependence on target strength. It is supposed that the constancy of echo-related AEP results from variation of hearing sensitivity depending on the target strength and release of echo-related responses from masking by transmitted pulses depending on the distance.
Supin
Alexander Ya
AY
Institute of Ecology and Evolution of the Russian Academy of Sciences, 33 Leninsky Prospect, 119071 Moscow, Russia. alex_supin@sevin.ru
Nachtigall
Paul E
PE
Au
Whitlow W L
WW
Breese
Marlee
M
D000818:Animals; D001288:Attention / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology; D004215:Distance Perception / Q000502:physiology*; D004289:Dolphins / Q000502:physiology*; D004455:Echolocation / Q000502:physiology*; D004569:Electroencephalography; D005071:Evoked Potentials / Q000502:physiology*; D009949:Orientation / Q000502:physiology*; D011571:Psychoacoustics; D013018:Sound Spectrography