Optokinetic nystagmus in harbor seals (Phoca vitulina)
F.D. Hanke, W. Hanke, K.-P. Hoffmann & G. Dehnhardt
Vision Res. 48: 304-315, 2008
- Harbor seals experience motion due to self-motion and to movement in the external world. However, motion vision
has not been studied yet in marine mammals moving in the underwater world. To open up this research, optokinetic
nystagmus (OKN) as a basic motion sensing and retinal image stabilizing reflex was studied in four harbor seals
during stimulation with moving black-and-white stripe patterns. All seals responded with optokinetic eye movements.
Detailed measurements obtained with one animal revealed a moderate gain for horizontal binocular OKN. Monocularly
stimulated, the seal displayed a symmetrical OKN with slightly stronger responses to leftward moving stimuli, and,
surprisingly, a symmetrical OKN was found in the vertical domain.
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