Title : Impact of Response Duration on Multisensory Integration

23 Multisensory neurons in the superior colliculus (SC) have been shown to have large 24 receptive fields that are heterogeneous in nature. These neurons have the capacity to 25 integrate their different sensory inputs, a process that has been shown to depend on the 26 physical characteristics of the stimuli that are combined (i.e., spatial and temporal 27 relationship and relative effectiveness). Recent work has highlighted the 28 interdependence of these factors in driving multisensory integration, adding a layer of 29 complexity to our understanding of multisensory processes. In the current study our 30 goal is to add to this understanding by characterizing how stimulus location impacts the 31 temporal dynamics of multisensory responses in cat SC neurons. The results illustrate 32 that locations within the spatial receptive fields (SRFs) of these neurons can be divided 33 into those showing short duration responses and long duration response profiles. Most 34 importantly, discharge duration appears to be a good determinant of multisensory 35 integration, such that short duration responses are typically associated with high 36 magnitude of multisensory integration (i.e., superadditive responses) while long duration 37 responses are typically associated with low integrative capacity. These results further 38 reinforce the complexity of the integrative features of SC neurons, and show that the 39 large SRFs of these neurons are characterized by vastly differing temporal dynamics; 40 dynamics that strongly shape the integrative capacity of these neurons. 41