Objective Many studies have reported that animals will display collision avoidance behavior when the size of retinal image of an object reaches a threshold.The present study aimed to investigate the neural correlates ...Objective Many studies have reported that animals will display collision avoidance behavior when the size of retinal image of an object reaches a threshold.The present study aimed to investigate the neural correlates underlying the frog collision avoidance behavior.Methods Different types of visual stimuli simulating the retinal image of an approaching or a recessing object were generated by a computer and presented to the right eye of frog.A multielectrode array was used to examine the activity of collision-sensitive neurons,and single electrode recordings were employed to quantify visual parameter （s）of the frog collision-sensitive neurons.Results The multielectrode array revealed that 40 neurons in the optic tectum showed selective responsiveness to objects approaching on a direct collision course.The response profiles of these collision-sensitive neurons were similar to those of lobula giantmovement detector（LGMD）in the locust or to those ofηneurons in the pigeon.However,the receptive field（RF）size of the frog neurons[（18.5±3.8）°,n=33）]was smaller than those of collision-sensitive neurons of the locust and the pigeon.Multielectrode recordings also showed that the collision-sensitive neurons were activated only when the focus of expansion of a looming retinal image was located within the center of its RF.There was a linear relationship between the parameter l/v（l denotes half-size of the object,v denotes approaching velocity） and time-to-collision（time difference between the peak of the neuronal activity and the predictive collision）in 16 collisionsensitive neurons.Theoretical consideration showed that the peak firing rate always occurred at a fixed delay of（60.1±39.5）ms （n=16）after the object had reached a constant angular size of（14.8±3.4）°（n=16）on the retina.Conclusion The results may help clarify the mechanisms underlying the collision avoidance behavior in bullfrog.展开更多
We study the top-quark pair production via polarized and unpolarized photon collisions at the International Linear Collider in the context of the littlest Higgs model with T-parity.We calculate the production cross se...We study the top-quark pair production via polarized and unpolarized photon collisions at the International Linear Collider in the context of the littlest Higgs model with T-parity.We calculate the production cross section of the process γγ→ tt and find the effects can be more significant in the (——) polarized photon collision mode than in other collision modes,and the relative correction can be expected to reach about 1% in the favorable parameter space.展开更多
基金supported by the 21st Century Program,committee of Education of Japan at the Kyushu Institute of Technology
文摘Objective Many studies have reported that animals will display collision avoidance behavior when the size of retinal image of an object reaches a threshold.The present study aimed to investigate the neural correlates underlying the frog collision avoidance behavior.Methods Different types of visual stimuli simulating the retinal image of an approaching or a recessing object were generated by a computer and presented to the right eye of frog.A multielectrode array was used to examine the activity of collision-sensitive neurons,and single electrode recordings were employed to quantify visual parameter （s）of the frog collision-sensitive neurons.Results The multielectrode array revealed that 40 neurons in the optic tectum showed selective responsiveness to objects approaching on a direct collision course.The response profiles of these collision-sensitive neurons were similar to those of lobula giantmovement detector（LGMD）in the locust or to those ofηneurons in the pigeon.However,the receptive field（RF）size of the frog neurons[（18.5±3.8）°,n=33）]was smaller than those of collision-sensitive neurons of the locust and the pigeon.Multielectrode recordings also showed that the collision-sensitive neurons were activated only when the focus of expansion of a looming retinal image was located within the center of its RF.There was a linear relationship between the parameter l/v（l denotes half-size of the object,v denotes approaching velocity） and time-to-collision（time difference between the peak of the neuronal activity and the predictive collision）in 16 collisionsensitive neurons.Theoretical consideration showed that the peak firing rate always occurred at a fixed delay of（60.1±39.5）ms （n=16）after the object had reached a constant angular size of（14.8±3.4）°（n=16）on the retina.Conclusion The results may help clarify the mechanisms underlying the collision avoidance behavior in bullfrog.
基金Supported by the National Natural Science Foundation of China under Grant Nos.10775039,11075045Specialized Research Fund for the Doctoral Program of Higher Education under Grant No.20094104110001HASTIT under Grant No.2009HASTIT004
文摘We study the top-quark pair production via polarized and unpolarized photon collisions at the International Linear Collider in the context of the littlest Higgs model with T-parity.We calculate the production cross section of the process γγ→ tt and find the effects can be more significant in the (——) polarized photon collision mode than in other collision modes,and the relative correction can be expected to reach about 1% in the favorable parameter space.
