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PLoS One. 2014 Aug 25;9(8):e105938. doi: 10.1371/journal.pone.0105938. eCollection 2014.

Cognitive adaptation of sonar gain control in the bottlenose dolphin.

Author information

1
Department of Neuroscience, Brown University, Providence, Rhode Island, United States of America; Electrical and Computer Engineering, University of Massachusetts Dartmouth, Dartmouth, Massachusetts, United States of America.
2
Department of Zoology, University of Hawaii, Honolulu, Hawaii, United States of America.
3
Electrical and Computer Engineering, University of Massachusetts Dartmouth, Dartmouth, Massachusetts, United States of America.
4
Department of Neuroscience, Brown University, Providence, Rhode Island, United States of America.

Abstract

Echolocating animals adjust the transmit intensity and receive sensitivity of their sonar in order to regulate the sensation level of their echoes; this process is often termed automatic gain control. Gain control is considered not to be under the animal's cognitive control, but previous investigations studied animals ensonifying targets or hydrophone arrays at predictable distances. To test whether animals maintain gain control at a fixed level in uncertain conditions, we measured changes in signal intensity for a bottlenose dolphin (Tursiops truncatus) detecting a target at three target distances (2.5, 4 and 7 m) in two types of sessions: predictable and unpredictable. Predictable sessions presented the target at a constant distance; unpredictable sessions moved the target randomly between the three target positions. In the predictable sessions the dolphin demonstrated intensity distance compensation, increasing the emitted click intensity as the target distance increased. Additionally, as trials within sessions progressed, the animal adjusted its click intensity even from the first click in a click train, which is consistent with the animal expecting a target at a certain range. In the unpredictable sessions there was no significant difference of intensity with target distance until after the 7th click in a click train. Together, these results demonstrate that the bottlenose dolphin uses learning and expectation for sonar gain control.

PMID:
25153530
PMCID:
PMC4143348
DOI:
10.1371/journal.pone.0105938
[Indexed for MEDLINE]
Free PMC Article

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