著者

Tomina Yusuke Takahata Masakazu

出版者

Elsevier

雑誌

Physiology & Behavior (ISSN:00319384)

巻号頁・発行日

vol.101, no.1, pp.108-116, 2010-08-04

被引用文献数

10

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Operant conditioning is a common tool for studying cognitive aspects of brain functions. As the first step toward understanding those functions in simple invertebrate microbrains, we tested whether operant conditioning could be applied to train American lobster Homarus americanus that has been extensively adopted as an animal model for neurophysiological analyses of nervous system functions and behavioral control. The animal was trained by food rewarding for gripping of a sensor bar as the operant behavior. Lobsters were first reinforced when they acted on the bar with a stronger grip than a pre-set value. After this reinforcement, the animal learnt to grip the bar for food pellets. The yoked control experiment in which the animal received action-independent reinforcement excluded the possibility of pseudoconditioning that the food simply drove the animal to frequent gripping of the sensor bar. The association of the bar grip with food was extinguished by rewarding nothing to the operant behavior, and was restored by repeating the reinforcement process as before. In addition, lobsters successfully carried out differential reinforcement regarding the gripping force: their gripping force changed depending on the increased force threshold for food reward. These data demonstrate that lobsters can be trained by operant conditioning paradigms involving acquisition and extinction procedures with the precise claw gripping even under the force control.

著者

Chikamoto Kyoko Kagaya Katsushi Takahata Masakazu

出版者

Zoological Society of Japan

雑誌

Zoological Science (ISSN:02890003)

巻号頁・発行日

vol.25, no.8, pp.783-792, 2008-08

被引用文献数

11

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Crayfish initiate walking behavior not only reflexively in response to external stimuli but also spontaneously in the absence of any specific stimulus. In order to analyze the initiation mechanism underlying these different types of walking, we made simultaneous electromyographic (EMG) recordings from thoracic legs when animals initiated walking, either reflexively or spontaneously, and video recorded their movements synchronously with the EMG recording. Two different stimuli, mechanical and chemical, were used to reflexively induce walking. A non-rhythmic, sustained activation of leg muscles was found to precede the behavioral initiation of either type of walking. The duration of this non-rhythmic muscle activation was significantly longer in the spontaneously initiated walking than in the mechanical stimulus-evoked walking, although no difference was observed between the spontaneous and chemical stimulus-evoked walking. EMG recordings from all eight legs revealed that their non-rhythmic muscle activation occurred almost simultaneously prior to initiation of rhythmical stepping movements. When an animal was suspended without a leg substratum, the timing of muscle activation was more variable among the legs than in the free condition on the substratum. When the circumesophageal commissures were both severed to eliminate signals descending from the brain to the thoracic ganglia, the bilaterally coordinated rhythmic burst activity was not observed in the walking legs. These findings suggest that the spontaneous initiation of walking behavior requires sensory feedback signals from leg proprioceptors, subserved by a different descending activation mechanism from that for stimulus-driven initiation of walking.