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Suryadeep Dash, Xiaogang Yan, Hongying Wang, J. Douglas Crawford; Continuous updating of superior colliculus visuospatial memory responses during smooth pursuit eye movements.. Journal of Vision 2012;12(9):992. doi: 10.1167/12.9.992.
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Spatial updating is a process that enables us to constantly compute spatial relationships between ourselves and the surrounding environment during self-motion. Primates are able to spatially update saccade targets across intervening saccade or smooth pursuit (SP) eye movements. Various studies have demonstrated discrete remapping of visual responses, in several brain structures, before and after the saccade. However, no study to date has shown continuous updating of such responses during the eye movement, nor has anyone published a study of the neural mechanism of spatial updating for SP. In this study we recorded superior-colliculus unit activity from 2 monkeys. Animals were trained to spatially update the location of a saccade target across an intervening SP. Neurons were characterized (as visual, visuo-motor or motor neurons) and their visual / motor receptive fields (RF) were specified using a delayed saccade paradigm. After this each neuron was tested in the SP-saccade paradigm. Saccade target direction and pursuit ramp length were varied such that (across trials) the remembered saccade target passed approximately through the neuron’s RF at 2-5 different points on the SP ramp. Of the 50 neurons analyzed to date, every neuron that showed a visual response (n=47), whether it was a visual and visuomotor neuron, exhibited a clear and robust modulation in activity when the location of remembered target passed across the RF of the neuron during SP. In contrast, none of the motor neurons showed any updating related response, but instead only burst for an intended saccade. We conclude that 1) the superior colliculus visual memory response is continuously updated during SP eye movements in a gaze-centered coordinates, and 2) only visual responses (not motor) are involved in visuospatial memory. This may reflect a general mechanism for continuous updating during slow self-motion.
Meeting abstract presented at VSS 2012
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