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
Objective Electrophysiological examination of the ipsilateral pretectotectal projection has proved that pretectal cells elicit strong suppressive responses to the ipsilateral tectum.However,the neural mechanisms under...Objective Electrophysiological examination of the ipsilateral pretectotectal projection has proved that pretectal cells elicit strong suppressive responses to the ipsilateral tectum.However,the neural mechanisms underlying the contralateral pretectotectal prejection are still obscure.The present study aimed to examine the synaptic nature of pretectal nuclei and contralateral tectal cells,and to demonstrate the spatiotemporal pattern of neuronal activity in the 2 main brain structures. Methods Intracellular recording and current source density（CSD）analysis were used to test the complexity of neuronal mechanism of pretectotectal information transfer.Results The pretectal stimulation elicited only one type of response on the contralateral tectum,the inhibitory postsynaptic potential（IPSP）.The majority of contra-induced IPSPs were assumed to be polysynaptically driven.In the CSD analysis,only one sink with short latency was observed in each profile.The ipsilateral projection produced a prominent monosynaptic sink in layer 8 of tectum.Recipient neurons were located in layers 6 and 7 of tectum.The result confirmed former findings from ipsilateral intracellular recordings.Conclusion These results suggest the following neuronal circuit：afferents from the pretectal nuclei broadly inhibit both tectal neuron,and since no second sink occurs in tectal layers,the pretectotectal excitatory afferents probably do not extend over the whole tectum,but are within limited state.The results of intracellular recording and CSD analysis further provide evidence of how pretectal afferent activity flows within the tectal laminae.展开更多
Objective A few investigations have been reported about pretectal suppressive influences on the optic tectum of frog, but characteristics of tectal activity to pretectal input are left unknown. We made intracellular r...Objective A few investigations have been reported about pretectal suppressive influences on the optic tectum of frog, but characteristics of tectal activity to pretectal input are left unknown. We made intracellular recordings to demonstrate the unexpected complexity in synaptic mechanisms involved in the suppressive influences of pretecal stimulation on the tectal cells. Methods In the present study, we investigated the neuronal activity evoked by pretectal （Lpd/P） nuclei stimulation using intracellular recording technique. Results The pretectal stimulation mainly elicited two types of responses in the ipsilateral tectum： an excitatory postsynaptic potential （EPSP） followed by an inhibitory postsynaptic potential （IPSP） and a pure IPSP. The latter predominated in the tectal cells responding to pretectal stimulation. In a few cells, biphasic hyperpolarization appeared under stronger stimulus intensities. The spikes of tecto-pretectal projecting cells elicited by antidromical stimulation were recorded in the ipsilateral tectum, which revealed reciprocal connections between the tectum and particular pretectal nuclei. The synaptic natures underlying pretecto-tectal information transformation have also been demonstrated. EPSPs with short latencies were concluded to be monosynaptic. Most IPSPs were generated through polysynaptic paths, but monosynaptic IPSPs were also recorded in the tectum. Nearly 98% of impaled tectal cells （except for antidromically projecting cells） showed inhibitory responses to pretectal stimulation. Conclusion The results provide strong evidence that pretectal cells broadly inhibit tectal neurons as that has suggested by behavioral and extracellular recording studies.展开更多
Some shallow and middle optic tectum(OT)neurons have stable,asymmetric full-screen ON and OFF stimulus response properties,which makes them candidates for delay encoding.In this paper,we investigated the de...Some shallow and middle optic tectum(OT)neurons have stable,asymmetric full-screen ON and OFF stimulus response properties,which makes them candidates for delay encoding.In this paper,we investigated the delay encoding mechanism for the neuronal clusters in the OT region of pigeons and determined the mechanism of delay coding in the OT region.By analyzing the responses of the neuron cluster under full-screen switch-on and switch-off stimulation,we found that the delay coding was widespread in the OT region where the ON/OFF stimulation time difference was 4-6 ms.Information theory analysis under grating stimulation and experiments based on single-neuron character reconstruction of neurons showed that OT neuron clusters use the first spike latency(FSL)for the rapid transfer of spatial structure information.Furthermore,4 models were used to predict the first spike latency of these OT neurons.The best simulation results were obtained using an architecture where the ON and OFF paths of multiple retinal ganglion cells(RGCs)were integrated and summed,respectively.展开更多
Using the blind patch-clamp technique with the whole-cell mode, we have studied the modulation of pre-synaptic receptor on postsynaptic g-aminobutyric acid (GABA) receptor measuring miniature inhibitory postsy-naptic ...Using the blind patch-clamp technique with the whole-cell mode, we have studied the modulation of pre-synaptic receptor on postsynaptic g-aminobutyric acid (GABA) receptor measuring miniature inhibitory postsy-naptic currents (mIPSCs) in optic tectum of Xenopus during critical peroid. It was demonstrated that compared with mature neurons, mIPSCs recorded from immature neurons had smaller amplitude and longer decay time. mIPSCs are mediated by GABAa receptor. The nicotinic acetylcholine receptor agonists (carbachol, cytisine, nicotine, DMPP and so on) could increase the frequency of mIPSCs. The enhance-ment of mIPSCs frequency induced by nAChR agonists was calcium-dependent. However, the choline, a product of hy-drolyzed acetylcholine, could not increase the frequency of mIPSCs. DH-b-E, a competitive antagonist of nAChR, blocked the increase of mIPSCs frequency induced by car-bachol. Mecamyllamine, an a3b4 subtype of nAChR antago-nist, also blocked the carbachol-induced enhancement of mIPSCs. On the other hand, MLA, a7 subtype of nAChR antagonist, had no effect on it. Thus, it seems that nAChR could presynaptically modulate the mIPSCs and a3b4 sub-type of nAChR might be involved. But a7 nAChR subtype of nAChR would not be involved. The modulation is calcium- dependent. Meanwhile, we found that Ca2+-free solution could elicit giant PSCs. The frequency of mIPSCs also is related with the level of HP.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 21st Century program,Committee of Education of Japan at the Kyushu Institute of Technology,and the Health Bureau of Shangdong Province,China
文摘Objective Electrophysiological examination of the ipsilateral pretectotectal projection has proved that pretectal cells elicit strong suppressive responses to the ipsilateral tectum.However,the neural mechanisms underlying the contralateral pretectotectal prejection are still obscure.The present study aimed to examine the synaptic nature of pretectal nuclei and contralateral tectal cells,and to demonstrate the spatiotemporal pattern of neuronal activity in the 2 main brain structures. Methods Intracellular recording and current source density（CSD）analysis were used to test the complexity of neuronal mechanism of pretectotectal information transfer.Results The pretectal stimulation elicited only one type of response on the contralateral tectum,the inhibitory postsynaptic potential（IPSP）.The majority of contra-induced IPSPs were assumed to be polysynaptically driven.In the CSD analysis,only one sink with short latency was observed in each profile.The ipsilateral projection produced a prominent monosynaptic sink in layer 8 of tectum.Recipient neurons were located in layers 6 and 7 of tectum.The result confirmed former findings from ipsilateral intracellular recordings.Conclusion These results suggest the following neuronal circuit：afferents from the pretectal nuclei broadly inhibit both tectal neuron,and since no second sink occurs in tectal layers,the pretectotectal excitatory afferents probably do not extend over the whole tectum,but are within limited state.The results of intracellular recording and CSD analysis further provide evidence of how pretectal afferent activity flows within the tectal laminae.
文摘Objective A few investigations have been reported about pretectal suppressive influences on the optic tectum of frog, but characteristics of tectal activity to pretectal input are left unknown. We made intracellular recordings to demonstrate the unexpected complexity in synaptic mechanisms involved in the suppressive influences of pretecal stimulation on the tectal cells. Methods In the present study, we investigated the neuronal activity evoked by pretectal （Lpd/P） nuclei stimulation using intracellular recording technique. Results The pretectal stimulation mainly elicited two types of responses in the ipsilateral tectum： an excitatory postsynaptic potential （EPSP） followed by an inhibitory postsynaptic potential （IPSP） and a pure IPSP. The latter predominated in the tectal cells responding to pretectal stimulation. In a few cells, biphasic hyperpolarization appeared under stronger stimulus intensities. The spikes of tecto-pretectal projecting cells elicited by antidromical stimulation were recorded in the ipsilateral tectum, which revealed reciprocal connections between the tectum and particular pretectal nuclei. The synaptic natures underlying pretecto-tectal information transformation have also been demonstrated. EPSPs with short latencies were concluded to be monosynaptic. Most IPSPs were generated through polysynaptic paths, but monosynaptic IPSPs were also recorded in the tectum. Nearly 98% of impaled tectal cells （except for antidromically projecting cells） showed inhibitory responses to pretectal stimulation. Conclusion The results provide strong evidence that pretectal cells broadly inhibit tectal neurons as that has suggested by behavioral and extracellular recording studies.
基金the National Natural Science Foundation of China(NSFC)General program(61673353)the Young Scientist Fund of NSFC(61603344)Key research projects of Higher Education of Henan Province of China(15A120017).
文摘Some shallow and middle optic tectum(OT)neurons have stable,asymmetric full-screen ON and OFF stimulus response properties,which makes them candidates for delay encoding.In this paper,we investigated the delay encoding mechanism for the neuronal clusters in the OT region of pigeons and determined the mechanism of delay coding in the OT region.By analyzing the responses of the neuron cluster under full-screen switch-on and switch-off stimulation,we found that the delay coding was widespread in the OT region where the ON/OFF stimulation time difference was 4-6 ms.Information theory analysis under grating stimulation and experiments based on single-neuron character reconstruction of neurons showed that OT neuron clusters use the first spike latency(FSL)for the rapid transfer of spatial structure information.Furthermore,4 models were used to predict the first spike latency of these OT neurons.The best simulation results were obtained using an architecture where the ON and OFF paths of multiple retinal ganglion cells(RGCs)were integrated and summed,respectively.
基金the Na-tional Natural Science Foundation of China (Grant No.39670774)
文摘Using the blind patch-clamp technique with the whole-cell mode, we have studied the modulation of pre-synaptic receptor on postsynaptic g-aminobutyric acid (GABA) receptor measuring miniature inhibitory postsy-naptic currents (mIPSCs) in optic tectum of Xenopus during critical peroid. It was demonstrated that compared with mature neurons, mIPSCs recorded from immature neurons had smaller amplitude and longer decay time. mIPSCs are mediated by GABAa receptor. The nicotinic acetylcholine receptor agonists (carbachol, cytisine, nicotine, DMPP and so on) could increase the frequency of mIPSCs. The enhance-ment of mIPSCs frequency induced by nAChR agonists was calcium-dependent. However, the choline, a product of hy-drolyzed acetylcholine, could not increase the frequency of mIPSCs. DH-b-E, a competitive antagonist of nAChR, blocked the increase of mIPSCs frequency induced by car-bachol. Mecamyllamine, an a3b4 subtype of nAChR antago-nist, also blocked the carbachol-induced enhancement of mIPSCs. On the other hand, MLA, a7 subtype of nAChR antagonist, had no effect on it. Thus, it seems that nAChR could presynaptically modulate the mIPSCs and a3b4 sub-type of nAChR might be involved. But a7 nAChR subtype of nAChR would not be involved. The modulation is calcium- dependent. Meanwhile, we found that Ca2+-free solution could elicit giant PSCs. The frequency of mIPSCs also is related with the level of HP.
