Auditory And Visual Spatial Discrimination And Multisensory Integration In Mouse Superior Colliculus Neurons

The superior colliculus(SC)of the midbrain plays an important role in locating external stimuli and initiating the orientation of the head,eyes and upper limbs.The intermediate and deep layers of SC receive visual,auditory and tactile inputs and can integrate these inputs.Previous studies regarding multisensory integration and spatial localization of stimuli in SC were mostly conducted in anesthetized animals.Therefore,it is still unclear how SC neurons localize a cue and integrate multisensory inputs when awake animals perform behavioral tasks.In this study,we trained C57BL/6 mice to perform a cue-location-discrimination task.The mice were required to judge whether the the triggered stimulus was derived from the left or right hemisfield(30° left and 30° right).We recorded SC neurons’response in task engagement using the multi-channels electrode recording.Our data show that more SC neurons could significantly discriminate the diference in cue locations in task engagement(that is,the response to the stimulus on one spatial location was significantly greater than that on the opposite side).Most of SC neurons examined prefer the stimulus located in the spatial field contralateral to SC.Also,we found that SC neurons showed the greater capability of spatial discrimination in multisensory conditions.Further study demonstrated that this improved capability of multisensory-cue localizations is closely related to the differential manner of multisensory integration that SC neurons used in task engagement(multisensory enhancement is mainly used in integrating cues on the contralateral hemisfield,and weak or no multisensory enhancement or even manner leads to an increase of the difference between neuron’s responses recordemultisensory inhibition is used on the ipsilateral side).This differential integrating d in different hemisfields.It should be noted that SC neurons also exhibited the differential integrating manner in the passive condition despite a less degree.In addition,we noticed that the spatial tuning of SC neurons is significantly enhanced in task engagement.Thus,these data greatly improve our understanding of the role of SC in spatial discrimination and multisensory integration.