Low frequency electroencephalogram oscillations govern left-eye lateralization during anti-predatory responses in the music frog

Abstract

Visual lateralization is widespread for prey and anti-predation in numerous taxa. However, it is still unknown how the brain governs this asymmetry. In this study, we conducted both behavioral and electrophysiological experiments to evaluate anti-predatory behaviors and dynamic brain activities in the Emei music frogs (Nidirana daunchina) in order to explore the potential eye bias for anti-predation and the underlying neural mechanism. To do this, the predator stimuli (the head of a snake model and leaf as control) were moved around the subjects in clockwise and anticlockwise at steady velocity, respectively. We counted the number of anti-predatory responses and measured electroencephalogram (EEG) power spectra for each band and each brain area (the telencephalon, diencephalon and mesencephalon). The results showed that: (1) no significant eye preferences could be found for the control (leaf), however, the laterality index was significantly lower than zero when the predator stimulus was moved anticlockwise, suggesting left-eye advantage exists in this species for anti-predation; (2) compared with no stimulus in the visual field, the power spectra of delta and alpha bands were significantly greater when the predator stimulus was moved into LVF anticlockwise; and (3) generally, the power spectra of each band in the right-hemisphere for LVF were higher than those in the left counterpart. These results support that the left-eye mediates monitoring of the predator in the music frogs and the lower frequency EEG oscillations govern this visual lateralization.