Accurate information on eye position in the orbit is available from visual feedback,efference copy of the oculomotor commands and proprioceptive signals from the extraocular muscles (EOM).Whereas visual feedback and o...Accurate information on eye position in the orbit is available from visual feedback,efference copy of the oculomotor commands and proprioceptive signals from the extraocular muscles (EOM).Whereas visual feedback and oculomotor commands have been extensively studied,central processing of EOM proprioceptive signals remains to be elucidated.A challenge to the field is to develop an approach to induce passive eye movements without physically contacting the eyes.A novel method was developed to generate passive eye movements in rats.A small rare-earth magnet disk (0.7 mm diameter,0.5 mm thickness) was attached to the surface of a rat's eyeball.A metal rod (5 mm diameter) wrapped with an electromagnetic (EM) coil was placed near the magnet (8-15 mm).By passing currents to the EM coil,electromagnetic force (EMF) was generated and acted upon the magnet and induced passive eye movements.The EMF induced well-defined passive eye movements,whose directions were dependent on current polarity and amplitudes and peak velocities were dependent on current intensity and duration.Peak velocities of the EMF-induced eye movements were linearly related to amplitudes,exhibiting main sequence relationships similar to that of saccades in awake rats and eye movements induced by electrical microstimulation of the abducens nucleus in anesthetized rats.Histological examination showed that repetitive EMF stimulations did not appear to result in damages in the EOM fibers.These results validated the EMF approach as a novel tool to investigate EOM proprioceptive signals and their roles in visual localization and gaze control.展开更多
We analyze the drawbacks of generally distributed time transition stochastic Petri nets(GDTT_SPN) in evaluating the performance of parallel systems,and propose a more general model,stochastic individual predicate/tran...We analyze the drawbacks of generally distributed time transition stochastic Petri nets(GDTT_SPN) in evaluating the performance of parallel systems,and propose a more general model,stochastic individual predicate/transition nets(SIPTN). SIPTN has higher modeling power and could provide more realistic models compared to GDTT_SPN,because in SIPTN the sojourn time distribution is determined not only by the transition,but also by the individuals. It is further proved that GDTT_SPN is a subset of SIPTN. As SIPTN introduces folding techniques from predicate/transition nets,SIPTN models have simpler and more intuitive graphic notations and accordingly higher usability,and thus are suitable for constructing simulation models for parallel systems.展开更多
基金supported by NIH grants to WZ(R21EY025550 R01DC014930)and HZ(R01DC012060)
文摘Accurate information on eye position in the orbit is available from visual feedback,efference copy of the oculomotor commands and proprioceptive signals from the extraocular muscles (EOM).Whereas visual feedback and oculomotor commands have been extensively studied,central processing of EOM proprioceptive signals remains to be elucidated.A challenge to the field is to develop an approach to induce passive eye movements without physically contacting the eyes.A novel method was developed to generate passive eye movements in rats.A small rare-earth magnet disk (0.7 mm diameter,0.5 mm thickness) was attached to the surface of a rat's eyeball.A metal rod (5 mm diameter) wrapped with an electromagnetic (EM) coil was placed near the magnet (8-15 mm).By passing currents to the EM coil,electromagnetic force (EMF) was generated and acted upon the magnet and induced passive eye movements.The EMF induced well-defined passive eye movements,whose directions were dependent on current polarity and amplitudes and peak velocities were dependent on current intensity and duration.Peak velocities of the EMF-induced eye movements were linearly related to amplitudes,exhibiting main sequence relationships similar to that of saccades in awake rats and eye movements induced by electrical microstimulation of the abducens nucleus in anesthetized rats.Histological examination showed that repetitive EMF stimulations did not appear to result in damages in the EOM fibers.These results validated the EMF approach as a novel tool to investigate EOM proprioceptive signals and their roles in visual localization and gaze control.
基金supported by the National Natural Science Foundation of China (No. 60576027)the Hi-Tech Research and Development Program (863) of China (No. 2006AA01Z415)
文摘We analyze the drawbacks of generally distributed time transition stochastic Petri nets(GDTT_SPN) in evaluating the performance of parallel systems,and propose a more general model,stochastic individual predicate/transition nets(SIPTN). SIPTN has higher modeling power and could provide more realistic models compared to GDTT_SPN,because in SIPTN the sojourn time distribution is determined not only by the transition,but also by the individuals. It is further proved that GDTT_SPN is a subset of SIPTN. As SIPTN introduces folding techniques from predicate/transition nets,SIPTN models have simpler and more intuitive graphic notations and accordingly higher usability,and thus are suitable for constructing simulation models for parallel systems.
