Local motion processing in the optic tectum of the Japanese toad, Bufo japonicus

Abstract

The results of previous behavioral studies can be so interpreted that the prey-catching behavior in the toad is elicited if there is a 'local' motion restricted within a small part of the visual field, while it is suppressed if there is a 'global' motion over a large part of the visual field. This has led us to design experiments to answer a specific question (yet a very essential one for understanding neural processes underlying this behavior): Are there 'local motion detectors' in the toad's visual system that are not activated by 'global' motion over a large part of the visual field but are activated by 'local' motion confined within a smaller part of it? The present study showed that (1) the majority of the toad's tectal neurons exhibit properties of the 'local motion detectors' as defined above, and (2) these properties can be explained from the receptive field structure revealed in the present experiments. Based on these results, we suggest that the tectal 'local motion detectors' are essential for the detection and localization of small moving prey-objects in the natural environment while ignoring the large moving objects or the self-induced motion of the visual field.

Prey capture in frogs: alternative strategies, biomechanical trade‐offs, and hierarchical decision making

“…However, vision appears to be the dominant sensory modality that most frogs use to detect prey. When vision is intact, frogs seldom attempt to capture stationary prey (Lettvin et al, '59; Ewert, '85; Satou and Shiraishi, ‘91). Frogs analyze prey characteristics visually before movement, and numerous previous studies have investigated the visual cues that frogs use in prey recognition (reviewed in Ewert, '87).…”

A gyroscopic advantage: phylogenetic patterns of compensatory movements in frogs

“…The higher head compensatory ability can be interpreted as a gyroscopic advantage in foraging and/or antipredator contexts. Visual cues are the dominant sensory modality that most frogs use to detect prey (Lettvin et al, 1959;Kaess and Kaess, 1960;Ewert, 1985;Satou and Shiraishi, 1991). A multidisciplinary neurobiological approach to the neural basis of visually guided prey-catching behavior revealed the concept of the key stimulus and releasing mechanism in toads (Ewert, 1985).…”

Experimental analysis of lizard pause-travel movement: pauses increase probability of prey capture

“…The experiment reported here tests the hypothesis that a pausing lizard will be more likely to detect and capture an item of invertebrate prey in its vicinity than a moving one. Lacertid lizards usually feed only on moving prey, as do many lower vertebrates (Ewert, 1985;Saton and Shiraishi, 1991; data relating to toads in both cases), and so the experiment utilised living prey which were themselves able to move.…”