An electromyographic analysis of electrically-evoked prey-catching behavior by means of stimuli applied to the optic tectum in the Japanese toad.

As a step toward elucidating the tectal-controlling functions for generating the prey-catching motor pattern, electrically-evoked "snapping" (the final consummatory phase of the prey-catching sequence) by means of stimuli applied to the optic tectum was analyzed using electromyographic methods in freely-moving Japanese toads. Electromyographic activities were recorded from the following 7 muscles in the head region (the presumed "snapping"-related muscles): M. depressor mandibulae, M. temporalis, M. sternohyoideus, M. geniohyoideus, M. genioglossus, M. hyoglossus, and M. submentalis. It was found that the characteristic activities evoked in these muscles were associated with jaw/tongue movements during the electrically-evoked "snapping". All of these muscles, except for sternohyoideus and geniohyoideus muscles, were activated in an all-or-nothing manner which corresponded to the elicitation of the electrically-evoked "snapping". It was suggested that such an all-or-nothing character may reflect an all-or-nothing property of the neuronal circuits for generating the prey-catching motor-pattern.