Marine Mammal Cognition
Sounds treatment in marine mammals
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Hemispheric brain treatment of communicative sounds in marine mammals brain.
Introduction
In humans the left hemisphere of the brain is dominant for processing language. Nowadays, one of the important challenges in Cognitive Neuroscience is to assess the evolutionary origins of this neuropsychological mechanism. Several experiments were conducted to show a lateralized treatment of social vocalizations in monkeys. Great apes like chimpanzees or gorillas, monkeys like rhesus (Macaca mulatta)(Heffner, 1982) , present such a brain treatment. Adult apes favored the right ear (left hemisphere) when vocalizations from their own repertoire are heard but favored the left ear when listening to heterospecific vocalizations (Hauser, 1994). It is also clear that communication is lateralized in birds, and in mice (Ehret, 1987).
Hypotheses
My advisors and I would like to test if
(i) hearing of communicative vocalizations is lateralized in marine mammals' brain
(ii) if, as suggested by a recent behavioral studie(Von Fersen and Güntürkün, 2000), brain treatment of vocalization in dolphins is under the responsability of the right hemisphere.
Experiments
In order to prove our hypothesis, an experimental set is conducted with sea lions (Zalophus californianus) housed in Nürnberg's Tiergarten and an adult male dolphin housed in Parc Asterix Delphinarium.
- A group of 7 sea lions is tested in a playback protocol inspired from primatology (M. Hauser, 1994).
- One sea lion and a dolphin are trained to pass a dichotic experiment test. (Damasio et al, 1976).
Conclusion
Comprehension of how communicative sounds are proceed within marine mammal brain will help us to better understand
- which brain features are important to deal with vocal communicative informations.
- which evolutionnary pressure are modeling the communicative part of the brain.
Some references
Kilian, A., von Fersen, L., Güntürkün, O. (2000). Lateralization of visuospatial processing in the bottlenose dolphin (Tursiops truncatus). Behav Brain Res 116: 211-215
