Impact of response duration on multisensory integration.

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